Refuse an exclude pattern that does not compile when the config loads (closes #455)

An exclude pattern that did not compile was skipped with a log warning during the backup, which then stored what it meant to leave out. Config.Validate now refuses such a pattern, global or per snapshot, naming the setting and quoting the pattern. The compile step moves to a new package, internal/exclude, which both the config and the scanner call.

Model: opus-5-5

README.md

@@ -313,12 +313,10 @@ when the next path element is a number (so
 `vaultik config set age_recipients.0 age1...` works on a file without
 `age_recipients`), otherwise as a map. If the config loads, a change after which
 it would not, such as `vaultik config set compression_level 99`, is refused and
-the file is left unchanged. A config that does not load, such as the one
+the file is left unchanged. A config that does not load is checked one setting
-`config init` writes before `storage_url` is set or one with a `${ENV:...}`
+at a time. Examples are the file `config init` writes before `storage_url` is
-reference to a variable not set in this shell, is checked one setting at a time:
+set, and one with a `${ENV:...}` reference to a variable not set in this shell.
-only a change after which the changed setting cannot be read, such as one giving
+In such a config, an unknown key or a value of the wrong type is refused.
-it the wrong type (a single value where a list belongs or a word where a number
-belongs), is refused.
 
 **`snapshot create`**: Perform incremental backup of configured snapshots.
 
@@ -1041,20 +1039,37 @@ is `git describe --tags --always --dirty`, which `script/version` runs for the
 A `docker build .` of a clone, with no build arguments, runs the same
 `git describe` (without `--dirty`) on the `.git` in its build context, so it
 stamps the same value for a clean commit; the build fails if the context carries
-`.git` and no version, commit or commit date comes out. A binary built without
+`.git` and no version, commit or commit date comes out. `make` outside a git
-git metadata reports `dev`, or `unknown` when `script/docker` or
+checkout and `docker build .` without `.git` both stamp `dev`. `script/docker`
-`script/cibuild` built it outside a git checkout.
+and `script/cibuild` stamp `unknown` when they run outside a git checkout.
+
+A binary built by plain `go install` or `go build` carries no stamped version.
+It reports the version Go recorded in it instead:
+
+- a `go install` of the tag `v1.0.0` → `v1.0.0`.
+- a `go build` of an untagged commit → a Go pseudo-version, such as
+  `v1.0.1-0.20261110231226-0123456789ab`.
+- a build where Go recorded no version → `dev`.
 
 `goreleaser` stamps a release binary with the tag minus its leading `v`, so the
 tag `v1.0.0` produces `vaultik 1.0.0`, matching the archive name
 `vaultik_1.0.0_linux_amd64.tar.gz`. `goreleaser --snapshot` stamps
 `dev-<12 chars of the commit sha>` rather than inventing the next patch number.
-`vaultik version` calls a build a development build when its version is `dev`,
+
-`unknown`, `dev-<sha>`, the short commit sha or `<tag>-<N>-g<short sha>`, with
+`vaultik version` calls a build a development build when its version is one of
-or without `-dirty`; only a plain tag, such as `v1.0.0` or `1.0.0`, is a
+these:
-release. If `script/version` cannot be run at all, `make` stops with an error
+
-instead of building an unversioned binary, and a binary that somehow carries an
+- `dev` or `unknown`.
-empty version string still reports itself as a development build.
+- `dev-<sha>`.
+- the short commit sha.
+- `<tag>-<N>-g<short sha>`.
+- a Go pseudo-version.
+- any version with a `-dirty` or `+dirty` suffix.
+
+Only a plain tag, such as `v1.0.0` or `1.0.0`, is a release. If `script/version`
+cannot be run at all, `make` stops with an error instead of building an
+unversioned binary. A binary stamped with an empty version reports the version
+Go recorded in it; if Go recorded none, it is a development build.
 
 ### cutting a release
 

configs/config.example.yml

@@ -295,6 +295,7 @@ storage_url: "rclone://myremote/path/to/backups"
 
 # Path to local SQLite index database
 # This database tracks file state for incremental backups
+# It must be an absolute path; ~ is expanded
 # Default: the platform data directory, e.g.
 #   macOS: ~/Library/Application Support/vaultik/index.sqlite
 #   Linux: ~/.local/share/vaultik/index.sqlite

go.mod

@@ -24,6 +24,7 @@ require (
 	github.com/stretchr/testify v1.11.1
 	go.uber.org/dig v1.19.0
 	go.uber.org/fx v1.24.0
+	golang.org/x/mod v0.29.0
 	golang.org/x/sync v0.18.0
 	golang.org/x/sys v0.38.0
 	golang.org/x/term v0.37.0

internal/blobgen/negative_test.go

@@ -2,8 +2,10 @@ package blobgen_test
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"testing"
+	"testing/iotest"
 
 	"filippo.io/age"
 	"github.com/stretchr/testify/assert"
@@ -120,6 +122,38 @@ func TestNewReaderTrailingAndGarbage(t *testing.T) {
 	})
 }
 
+// TestNewReaderGarbageErrorQuotesNoBytes checks that lines of text in
+// place of a blob fail with ErrNotAgeStream, and that the error carries
+// none of their bytes. The lines end in a newline because age's own error
+// quotes the data's first line only when it reads a whole line.
+func TestNewReaderGarbageErrorQuotesNoBytes(t *testing.T) {
+	t.Parallel()
+
+	id, _ := makeIdentity(t)
+	garbage := bytes.Repeat([]byte("garbage-bytes-\n"), 100)
+
+	_, err := blobgen.NewReader(bytes.NewReader(garbage), id)
+
+	require.ErrorIs(t, err, blobgen.ErrNotAgeStream)
+	assert.NotContains(t, err.Error(), "garbage-bytes-")
+}
+
+// errConnectionReset stands for a storage read that fails.
+var errConnectionReset = errors.New("connection reset")
+
+// TestNewReaderReadFailure checks that a failed read of the age header is
+// returned as that read error, not as ErrNotAgeStream.
+func TestNewReaderReadFailure(t *testing.T) {
+	t.Parallel()
+
+	id, _ := makeIdentity(t)
+
+	_, err := blobgen.NewReader(iotest.ErrReader(errConnectionReset), id)
+
+	require.ErrorIs(t, err, errConnectionReset)
+	assert.NotErrorIs(t, err, blobgen.ErrNotAgeStream)
+}
+
 // TestNewWriterInvalidLevel covers the rejected end of issue case 9: an
 // out-of-range compression level errors and writes nothing to the destination.
 func TestNewWriterInvalidLevel(t *testing.T) {

internal/blobgen/reader.go

@@ -11,6 +11,11 @@ import (
 	"github.com/klauspost/compress/zstd"
 )
 
+// ErrNotAgeStream is returned by NewReader when the data cannot be opened
+// as an age stream, for example because its header is malformed. It
+// replaces age's own error, which can quote the data's first bytes.
+var ErrNotAgeStream = errors.New("not a valid age stream")
+
 // Reader wraps decompression and decryption with SHA256 verification
 type Reader struct {
 	reader       io.Reader
@@ -24,11 +29,25 @@ type Reader struct {
 // NewReader creates a new Reader that decrypts, decompresses, and verifies
 // data. Every supplied identity is offered to age.Decrypt, so a blob
 // encrypted to any one of them can be read.
+//
+// A failure to read r is returned as that error, and a blob encrypted to
+// none of the identities as age.NoIdentityMatchError. Any other failure
+// to open the age stream is ErrNotAgeStream.
 func NewReader(r io.Reader, identities ...age.Identity) (*Reader, error) {
-	// Create decryption reader
+	src := &readErrorRecorder{reader: r}
-	decReader, err := age.Decrypt(r, identities...)
+
+	decReader, err := age.Decrypt(src, identities...)
 	if err != nil {
+		var noMatch *age.NoIdentityMatchError
+
+		switch {
+		case src.err != nil:
+			return nil, fmt.Errorf("reading age header: %w", src.err)
+		case errors.As(err, &noMatch):
 			return nil, fmt.Errorf("creating decryption reader: %w", err)
+		default:
+			return nil, ErrNotAgeStream
+		}
 	}
 
 	// Create decompression reader
@@ -52,6 +71,23 @@ func NewReader(r io.Reader, identities ...age.Identity) (*Reader, error) {
 	}, nil
 }
 
+// readErrorRecorder passes reads through to reader and keeps the first
+// error other than io.EOF, so NewReader can tell a failed read from bad
+// data.
+type readErrorRecorder struct {
+	reader io.Reader
+	err    error
+}
+
+func (r *readErrorRecorder) Read(p []byte) (int, error) {
+	n, err := r.reader.Read(p)
+	if err != nil && !errors.Is(err, io.EOF) && r.err == nil {
+		r.err = err
+	}
+
+	return n, err
+}
+
 // Read implements io.Reader
 func (r *Reader) Read(p []byte) (int, error) {
 	n, err := r.teeReader.Read(p)

internal/cli/app.go

@@ -7,11 +7,9 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"path/filepath"
 	"sync"
 	"time"
 
-	"github.com/adrg/xdg"
 	"github.com/spf13/cobra"
 	"go.uber.org/dig"
 	"go.uber.org/fx"
@@ -339,7 +337,7 @@ func runVaultikApp(
 		},
 		Mode: mode,
 	}, op, func(err error) {
-		log.Error(failMsg, "error", err)
+		log.Info(failMsg, "error", err)
 		ReportErrorf("%s: %v", failMsg, err)
 	})
 }
@@ -351,8 +349,7 @@ func runVaultikApp(
 // only one runs at a time; a read-only command runs without it and is not
 // blocked while a mutator holds the lock (opts.Mode).
 func RunWithApp(ctx context.Context, opts AppOptions) error {
-	release, err := acquireLockIfMutating(opts.Mode,
+	release, err := acquireLockIfMutating(opts.Mode, pidlock.Dir())
-		filepath.Join(xdg.DataHome, "vaultik"))
 	if err != nil {
 		return err
 	}

internal/cli/config.go

@@ -49,8 +49,14 @@ var (
 	errWouldNotLoad     = errors.New(
 		"vaultik would not load the config after this change, " +
 			"so the file was not changed")
+	errSetS3KeysFirst = errors.New(
+		"set s3.access_key_id and s3.secret_access_key first, " +
+			"then storage_url")
 )
 
+// storageURLKey is the config key that selects the storage backend.
+const storageURLKey = "storage_url"
+
 // macOS is the value of runtime.GOOS on macOS.
 const macOS = "darwin"
 
@@ -276,7 +282,8 @@ storage_url: ""
 # Hostname used in snapshot IDs. Default: system hostname.
 # hostname: myserver
 
-# Path to the local SQLite index database.
+# Path to the local SQLite index database. It must be an absolute path;
+# ~ is expanded.
 # Default: the platform data directory, e.g.
 #   macOS: ~/Library/Application Support/vaultik/index.sqlite
 #   Linux: ~/.local/share/vaultik/index.sqlite
@@ -443,11 +450,10 @@ number, otherwise as a map.
 
 If the config loads, a change after which it would not, such as
 compression_level 99, is refused and the file is left unchanged. A
-config that does not load, such as the one config init writes before
+config that does not load is checked one setting at a time. Examples
-storage_url is set or one with a ${ENV:...} reference to a variable
+are the file config init writes before storage_url is set, and one
-not set here, is checked one setting at a time: only a change after
+with a ${ENV:...} reference to a variable not set in this shell. In
-which the changed setting cannot be read, such as one giving it the
+such a config, an unknown key or a value of the wrong type is refused.
-wrong type, is refused.
 
 Examples:
   vaultik config set storage_url "file:///mnt/backups"
@@ -484,6 +490,13 @@ func writeConfigSet(out *ui.Writer, path, key, value string) error {
 
 	keys := strings.Split(key, ".")
 
+	if keys[0] != config.EnvSection {
+		_, err = config.SettingType(keys)
+		if err != nil {
+			return err
+		}
+	}
+
 	err = yamlPathSet(root, keys, value)
 	if err != nil {
 		return err
@@ -506,7 +519,7 @@ func writeConfigSet(out *ui.Writer, path, key, value string) error {
 
 	err = checkConfigChange(oldData, data, settingData)
 	if err != nil {
-		return fmt.Errorf("%w: %w", errWouldNotLoad, err)
+		return wouldNotLoadError(key, err)
 	}
 
 	err = os.WriteFile(path, data, configFileMode)
@@ -530,6 +543,21 @@ func writeConfigSet(out *ui.Writer, path, key, value string) error {
 	return nil
 }
 
+// wouldNotLoadError returns the refusal of a change to key that vaultik
+// would not load for reason. When storage_url moves to s3:// before the S3
+// credentials are set, it says to set them first: they can be set while
+// the old storage_url is still in place.
+func wouldNotLoadError(key string, reason error) error {
+	if key == storageURLKey &&
+		(errors.Is(reason, config.ErrS3KeyIDRequired) ||
+			errors.Is(reason, config.ErrS3SecretRequired)) {
+		return fmt.Errorf("%w: %w; %w", errWouldNotLoad, reason,
+			errSetS3KeysFirst)
+	}
+
+	return fmt.Errorf("%w: %w", errWouldNotLoad, reason)
+}
+
 // checkConfigChange returns the reason vaultik would not load newData, the
 // config after a change, if the change brings that failure in. If oldData,
 // the config before it, loads, the new one must load too. A config that
@@ -739,41 +767,11 @@ func yamlPathSet(root *yaml.Node, keys []string, value string) error {
 }
 
 // configKeyIsString reports whether the dotted key names a string in
-// config.Config, following the fields' yaml tags, as s3.access_key_id and
+// config.Config, as s3.access_key_id and snapshots.home.exclude.0 do.
-// snapshots.home.exclude.0 do.
 func configKeyIsString(keys []string) bool {
-	typ := reflect.TypeFor[config.Config]()
+	typ, err := config.SettingType(keys)
 
-	for _, key := range keys {
+	return err == nil && typ.Kind() == reflect.String
-		switch {
-		case typ.Kind() == reflect.Map || typ.Kind() == reflect.Slice:
-			// The key is a snapshot name or a list index.
-			typ = typ.Elem()
-		case typ.Kind() == reflect.Struct:
-			field, ok := yamlField(typ, key)
-			if !ok {
-				return false
-			}
-
-			typ = field.Type
-		default:
-			return false
-		}
-	}
-
-	return typ.Kind() == reflect.String
-}
-
-// yamlField returns the field of struct type typ whose yaml tag names key.
-func yamlField(typ reflect.Type, key string) (reflect.StructField, bool) {
-	for field := range typ.Fields() {
-		name, _, _ := strings.Cut(field.Tag.Get("yaml"), ",")
-		if name == key {
-			return field, true
-		}
-	}
-
-	return reflect.StructField{}, false
 }
 
 // yamlSetInMapping resolves (creating if needed) the value node for the

internal/cli/config_test.go

@@ -2,6 +2,7 @@ package cli //nolint:testpackage // exercises unexported yamlPathGet/yamlPathSet
 
 import (
 	"bytes"
+	"errors"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -152,6 +153,21 @@ snapshots:
       - "~"
 `
 
+// testS3URL is an S3 storage_url, which needs credentials to load.
+const testS3URL = "s3://bucket/prefix?endpoint=https://s3.example.com"
+
+// configWithS3Keys loads: its storage_url is testS3URL and both S3 keys are
+// set.
+const configWithS3Keys = storageURLKey + ": " + testS3URL + `
+s3:
+  access_key_id: AKIAEXAMPLE
+  secret_access_key: example-secret
+snapshots:
+  home:
+    paths:
+      - "~"
+`
+
 // configWithUnsetReference loads only where VAULTIK_TEST_UNSET_SECRET is
 // set, as a backup job's environment might set it. No test sets it.
 const configWithUnsetReference = configWithoutRecipients + `s3:
@@ -225,7 +241,7 @@ func TestConfigSetIndexUnderMissingKey(t *testing.T) {
 // change after which the config would not load, with an error giving the
 // reason, and leaves the file as it was. On the file `config init` writes,
 // which does not load until storage_url is set, and on one that cannot be
-// read here, only a value of the wrong type is refused.
+// read here, only an unknown key or a value of the wrong type is refused.
 func TestConfigSetKeepsFileThatWouldNotLoad(t *testing.T) {
 	t.Parallel()
 
@@ -237,6 +253,14 @@ func TestConfigSetKeepsFileThatWouldNotLoad(t *testing.T) {
 		value  string
 		reason string
 	}{
+		// Keys that no setting has, on a config that loads and on one
+		// that does not.
+		{configWithoutRecipients, "nosuchkey", "1",
+			`unknown config key "nosuchkey"`},
+		{configWithoutRecipients, "snapshots.home.exlude", "/tmp",
+			`unknown config key "snapshots.home.exlude"`},
+		{defaultConfigText(macOS), "compression_lvl", "9",
+			`unknown config key "compression_lvl"`},
 		// Index 1 of the empty list the missing key gives.
 		{configWithoutRecipients, "age_recipients.1", testRecipient,
 			"index out of range"},
@@ -244,12 +268,20 @@ func TestConfigSetKeepsFileThatWouldNotLoad(t *testing.T) {
 		{configWithoutRecipients, "snapshots.home.paths", "/srv",
 			"into []string"},
 		{configWithoutRecipients, "chunk_size", "fast",
-			"invalid size format"},
+			`chunk_size: "fast" is not a size`},
 		// Values of the right type that fail validation.
 		{configWithoutRecipients, "compression_level", "99",
 			"compression_level must be between 1 and 19"},
 		{configWithoutRecipients, "chunk_size", "1KB",
 			"chunk_size must be at least 1MB"},
+		// An s3:// URL before its credentials names them.
+		{configWithoutRecipients, storageURLKey, testS3URL,
+			"s3.access_key_id is required for s3:// URLs; " +
+				"set s3.access_key_id and s3.secret_access_key first"},
+		{configWithoutRecipients + "s3:\n  access_key_id: AKIAEXAMPLE\n",
+			storageURLKey, testS3URL,
+			"s3.secret_access_key is required for s3:// URLs; " +
+				"set s3.access_key_id and s3.secret_access_key first"},
 		// With its reference filled in, the config loads.
 		{levelReference, "blob_size_limit", "1MB",
 			"blob_size_limit must be at least"},
@@ -335,6 +367,109 @@ func TestConfigSetRefusesOnlyItsOwnFailure(t *testing.T) {
 	}
 }
 
+// TestConfigSetS3KeysBeforeStorageURL checks that the order the refusal
+// gives works on a config that loads with a file:// storage_url.
+func TestConfigSetS3KeysBeforeStorageURL(t *testing.T) {
+	t.Parallel()
+
+	path := filepath.Join(t.TempDir(), "config.yml")
+
+	err := os.WriteFile(path, []byte(configWithoutRecipients), configFileMode)
+	if err != nil {
+		t.Fatalf("write config: %v", err)
+	}
+
+	for _, set := range [][2]string{
+		{"s3.access_key_id", "AKIAEXAMPLE"},
+		{"s3.secret_access_key", "example-secret"},
+		{storageURLKey, testS3URL},
+	} {
+		err = writeConfigSet(ui.NewWithColor(&bytes.Buffer{}, false),
+			path, set[0], set[1])
+		if err != nil {
+			t.Fatalf("config set %s: %v", set[0], err)
+		}
+	}
+
+	data, err := os.ReadFile(path) //nolint:gosec // G304: test-controlled path
+	if err != nil {
+		t.Fatalf("read config: %v", err)
+	}
+
+	if !strings.Contains(string(data), storageURLKey+": "+testS3URL) {
+		t.Errorf("config set storage_url wrote:\n%s", data)
+	}
+}
+
+// TestConfigSetRefusesClearingS3Key checks that clearing s3.access_key_id on
+// a config with an s3:// storage_url is refused without saying to set the
+// S3 keys first. That advice is only for a change to storage_url.
+func TestConfigSetRefusesClearingS3Key(t *testing.T) {
+	t.Parallel()
+
+	const key = "s3.access_key_id"
+
+	path := filepath.Join(t.TempDir(), "config.yml")
+
+	err := os.WriteFile(path, []byte(configWithS3Keys), configFileMode)
+	if err != nil {
+		t.Fatalf("write config: %v", err)
+	}
+
+	err = writeConfigSet(ui.NewWithColor(&bytes.Buffer{}, false), path, key, "")
+	if !errors.Is(err, errWouldNotLoad) {
+		t.Errorf("clearing %s gives error %v, want one saying %q",
+			key, err, errWouldNotLoad)
+	}
+
+	if errors.Is(err, errSetS3KeysFirst) {
+		t.Errorf("clearing %s gives error %v, want one not saying %q",
+			key, err, errSetS3KeysFirst)
+	}
+
+	data, err := os.ReadFile(path) //nolint:gosec // G304: test-controlled path
+	if err != nil {
+		t.Fatalf("read config: %v", err)
+	}
+
+	if string(data) != configWithS3Keys {
+		t.Errorf("clearing %s changed the file to:\n%s", key, data)
+	}
+}
+
+// TestConfigSetWritesEnvSection checks that config set writes a key under
+// the top-level env section, whose keys are not settings, on a config that
+// loads.
+func TestConfigSetWritesEnvSection(t *testing.T) {
+	const name = "VAULTIK_TEST_CONFIG_SET_ENV"
+
+	// Loading the changed config sets the variable; t.Setenv restores it
+	// after the test.
+	t.Setenv(name, "")
+
+	path := filepath.Join(t.TempDir(), "config.yml")
+
+	err := os.WriteFile(path, []byte(configWithoutRecipients), configFileMode)
+	if err != nil {
+		t.Fatalf("write config: %v", err)
+	}
+
+	err = writeConfigSet(ui.NewWithColor(&bytes.Buffer{}, false),
+		path, "env."+name, "value")
+	if err != nil {
+		t.Fatalf("config set env.%s: %v", name, err)
+	}
+
+	data, err := os.ReadFile(path) //nolint:gosec // G304: test-controlled path
+	if err != nil {
+		t.Fatalf("read config: %v", err)
+	}
+
+	if !strings.Contains(string(data), "env:\n  "+name+": value\n") {
+		t.Errorf("config set env.%s wrote:\n%s", name, data)
+	}
+}
+
 // TestConfigSetStringLooksLikeNumber sets string settings to values that
 // YAML reads as numbers or booleans when they are unquoted, and checks that
 // config.Load returns each one unchanged.

internal/cli/database.go

@@ -6,7 +6,9 @@ import (
 
 	"github.com/spf13/cobra"
 	"sneak.berlin/go/vaultik/internal/config"
+	"sneak.berlin/go/vaultik/internal/database"
 	"sneak.berlin/go/vaultik/internal/log"
+	"sneak.berlin/go/vaultik/internal/vaultik"
 )
 
 // NewDatabaseCommand creates the database command group
@@ -90,26 +92,24 @@ Use --force to skip the confirmation prompt.`,
 
 				var confirm string
 
-				_, err = fmt.Scanln(&confirm)
+				// A failure to read the answer means no confirmation.
+				_, err = fmt.Fscanln(cmd.InOrStdin(), &confirm)
 				if err != nil || confirm != "yes" {
 					_, _ = fmt.Fprintln(w, "Aborted.")
 
-					//nolint:nilerr // a failed/aborted confirmation is a clean abort
+					return vaultik.ErrNotConfirmed
-					return nil
 				}
 			}
 
-			// Delete the database file
+			// Delete the database file and its side files. A side file
-			err = os.Remove(dbPath)
+			// may not exist, so only failing to delete the database file
-			if err != nil {
+			// is an error.
+			for _, indexFile := range database.IndexFiles(dbPath) {
+				err = os.Remove(indexFile)
+				if err != nil && indexFile == dbPath {
 					return fmt.Errorf("failed to delete database: %w", err)
 				}
-
+			}
-			// Also delete WAL and SHM files if they exist
-			walPath := dbPath + "-wal"
-			shmPath := dbPath + "-shm"
-			_ = os.Remove(walPath) // Ignore errors - files may not exist
-			_ = os.Remove(shmPath)
 
 			out.Infof("Local state database deleted: %s.", dbPath)
 			log.Info("Local state database deleted", "path", dbPath)

internal/cli/database_test.go

@@ -0,0 +1,75 @@
+package cli //nolint:testpackage // sets the unexported rootFlags directly
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"sneak.berlin/go/vaultik/internal/database"
+	"sneak.berlin/go/vaultik/internal/vaultik"
+)
+
+// TestDatabaseDeleteDeclinedIsError checks that answering anything but
+// "yes" keeps the database and returns ErrNotConfirmed, so the command
+// exits non-zero.
+//
+//nolint:paralleltest // mutates the process-global rootFlags
+func TestDatabaseDeleteDeclinedIsError(t *testing.T) {
+	dir := t.TempDir()
+	dbPath, cfgPath := seedDatabaseDeleteConfig(t, dir)
+
+	setRootFlags(t, RootFlags{ConfigPath: cfgPath})
+
+	var out bytes.Buffer
+
+	cmd := newDatabaseDeleteCommand()
+	cmd.SetOut(&out)
+	cmd.SetErr(io.Discard)
+	cmd.SetIn(strings.NewReader("no\n"))
+	cmd.SetArgs(nil)
+
+	err := cmd.Execute()
+	if !errors.Is(err, vaultik.ErrNotConfirmed) {
+		t.Errorf("declined database delete returned %v, want %v",
+			err, vaultik.ErrNotConfirmed)
+	}
+
+	_, err = os.Stat(dbPath)
+	if err != nil {
+		t.Errorf("declined database delete removed the file: %v", err)
+	}
+
+	if !strings.Contains(out.String(), "Aborted.") {
+		t.Errorf("declined database delete printed %q, want Aborted.",
+			out.String())
+	}
+}
+
+// TestDatabaseDeleteRemovesSideFiles checks that the side files SQLite
+// keeps beside the database file are deleted with it.
+//
+//nolint:paralleltest // mutates the process-global rootFlags
+func TestDatabaseDeleteRemovesSideFiles(t *testing.T) {
+	dir := t.TempDir()
+	dbPath, cfgPath := seedDatabaseDeleteConfig(t, dir)
+
+	indexFiles := database.IndexFiles(dbPath)
+	for _, indexFile := range indexFiles {
+		seedFile(t, dir, filepath.Base(indexFile), "data")
+	}
+
+	setRootFlags(t, RootFlags{ConfigPath: cfgPath})
+
+	mustExecute(t, newDatabaseDeleteCommand(), "--force")
+
+	for _, indexFile := range indexFiles {
+		_, err := os.Stat(indexFile)
+		if !os.IsNotExist(err) {
+			t.Errorf("database delete left %s: stat err = %v", indexFile, err)
+		}
+	}
+}

internal/cli/entry.go

@@ -21,6 +21,8 @@ const shortCommitLen = 12
 const exitCodeInterrupted = 130
 
 // Entry is the main entry point for the CLI application.
+// It first calls globals.FillUnsetFromBuildInfo, which fills in the
+// version, commit and commit date that the linker flags did not set.
 // It prints the startup banner to stderr (unless a banner-suppressing
 // flag is present in os.Args — see bannerSuppressedInArgs), executes the
 // root cobra command, and routes any returned error through the
@@ -33,6 +35,7 @@ const exitCodeInterrupted = 130
 // deferred profile writers run before the process ends. See run in
 // cmd/vaultik/main.go.
 func Entry() int {
+	globals.FillUnsetFromBuildInfo()
 	emitStartupBanner(os.Args[1:], os.Stderr)
 
 	rootCmd := NewRootCommand()
@@ -82,6 +85,10 @@ func emitStartupBanner(args []string, w io.Writer) {
 // 🛑 ERROR: format. Use it from goroutine error paths (where returning
 // an error to cobra isn't an option) and anywhere else a CLI command
 // must surface a failure outside the normal RunE return path.
+//
+// This line is the one report of the failure. A caller that also logs
+// the failure logs it at info level, so the record appears only under
+// --verbose or --debug and the error is not printed twice.
 func ReportErrorf(format string, args ...any) {
 	ui.New(os.Stderr).Errorf(format, args...)
 }

internal/cli/entry_failure_once_test.go

@@ -0,0 +1,205 @@
+package cli //nolint:testpackage // shares the fixtures and capture helpers
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"filippo.io/age"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/vaultik/internal/database"
+	"sneak.berlin/go/vaultik/internal/ui"
+)
+
+const (
+	// errorLinePrefix starts the final line that reports a failed command.
+	errorLinePrefix = "ERROR: "
+
+	flagVerbose = "--verbose"
+	cmdRestore  = "restore"
+
+	// blobsDir is the directory of a destination store that holds the
+	// blobs.
+	blobsDir = "blobs"
+)
+
+// TestEntryFailureIsPrintedOnce runs commands that fail after startup
+// against a destination they cannot use. `info` is not among them: it
+// cannot fail after startup.
+//
+//nolint:paralleltest // replaces os.Args, os.Stdout, os.Stderr and the xdg globals
+func TestEntryFailureIsPrintedOnce(t *testing.T) {
+	for _, command := range [][]string{
+		{cmdSnapshot, cmdCreate},
+		{cmdSnapshot, cmdRemove, someSnapshotID},
+		{cmdSnapshot, cmdVerify, someSnapshotID},
+		{cmdRemote, cmdInfo},
+		{cmdPrune, flagJSON},
+	} {
+		for _, verbose := range []bool{false, true} {
+			name := fmt.Sprintf("%s verbose=%t", strings.Join(command, " "), verbose)
+
+			t.Run(name, func(t *testing.T) {
+				requireErrorPrintedOnce(t, verbose, append([]string{flagConfig,
+					writeUnusableDestinationConfig(t)}, command...)...)
+			})
+		}
+	}
+}
+
+// TestEntryBlobUploadFailureIsPrintedOnce backs up to a destination
+// whose blobs directory is a file, so the blob upload fails.
+//
+//nolint:paralleltest // replaces os.Args, os.Stdout, os.Stderr and the xdg globals
+func TestEntryBlobUploadFailureIsPrintedOnce(t *testing.T) {
+	for _, verbose := range []bool{false, true} {
+		t.Run(fmt.Sprintf("verbose=%t", verbose), func(t *testing.T) {
+			configPath, storeDir := writeBackupConfig(t)
+
+			require.NoError(t, os.WriteFile(
+				filepath.Join(storeDir, blobsDir), nil, 0o600))
+
+			requireErrorPrintedOnce(t, verbose,
+				flagConfig, configPath, cmdSnapshot, cmdCreate)
+		})
+	}
+}
+
+// TestEntryBlobDownloadFailureIsPrintedOnce backs up, deletes the blobs
+// from the destination, and restores, so the blob download fails.
+//
+//nolint:paralleltest // replaces os.Args, os.Stdout, os.Stderr and the xdg globals
+func TestEntryBlobDownloadFailureIsPrintedOnce(t *testing.T) {
+	for _, verbose := range []bool{false, true} {
+		t.Run(fmt.Sprintf("verbose=%t", verbose), func(t *testing.T) {
+			configPath, storeDir := writeBackupConfigWithPrivateKey(t)
+
+			code, _, _ := runEntry(t,
+				flagConfig, configPath, cmdSnapshot, cmdCreate)
+			require.Equal(t, 0, code)
+
+			require.NoError(t, os.RemoveAll(filepath.Join(storeDir, blobsDir)))
+
+			requireErrorPrintedOnce(t, verbose, flagConfig, configPath,
+				cmdSnapshot, cmdRestore, onlySnapshotID(t, configPath), t.TempDir())
+		})
+	}
+}
+
+// requireErrorPrintedOnce runs Entry with args, adding --verbose when
+// verbose is set. The command must fail, and stderr must carry its error
+// once, as the final ERROR: line. A log record carrying the same error
+// appears only under --verbose.
+func requireErrorPrintedOnce(t *testing.T, verbose bool, args ...string) {
+	t.Helper()
+
+	if verbose {
+		args = append(args, flagVerbose)
+	}
+
+	code, _, stderr := runEntry(t, args...)
+	require.Equal(t, 1, code)
+
+	errorLine, records := failureOutput(t, stderr)
+
+	if !verbose {
+		assert.Zero(t, records,
+			"without --verbose no log record repeats the error:\n%s", stderr)
+
+		return
+	}
+
+	assert.NotZero(t, records,
+		"--verbose must keep the log record of %q", errorLine)
+}
+
+// failureOutput requires stderr to hold exactly one ERROR: line and
+// returns it, with the number of log records whose error attribute is
+// the error that line reports. stderr is a pipe here, so every log
+// record is a JSON object on its own line.
+func failureOutput(t *testing.T, stderr string) (string, int) {
+	t.Helper()
+
+	var (
+		errorLines []string
+		records    []map[string]any
+	)
+
+	for line := range strings.Lines(stderr) {
+		var record map[string]any
+		if json.Unmarshal([]byte(line), &record) == nil {
+			records = append(records, record)
+
+			continue
+		}
+
+		if strings.Contains(line, errorLinePrefix) {
+			errorLines = append(errorLines, strings.TrimSpace(line))
+		}
+	}
+
+	require.Len(t, errorLines, 1,
+		"the error must be printed once as an ERROR: line:\n%s", stderr)
+
+	// An error can run over several lines; the ERROR: line holds the
+	// first of them.
+	repeats := 0
+
+	for _, record := range records {
+		failure, ok := record["error"].(string)
+		firstLine, _, _ := strings.Cut(failure, "\n")
+
+		if ok && strings.Contains(errorLines[0], firstLine) {
+			repeats++
+		}
+	}
+
+	return errorLines[0], repeats
+}
+
+// writeBackupConfigWithPrivateKey builds what writeBackupConfig builds,
+// with a generated key pair in place of its recipient. The config also
+// holds the private key, so that restore can decrypt the backup. Returns
+// the config path and the store directory.
+func writeBackupConfigWithPrivateKey(t *testing.T) (string, string) {
+	t.Helper()
+
+	configPath, storeDir := writeBackupConfig(t)
+
+	identity, err := age.GenerateX25519Identity()
+	require.NoError(t, err)
+
+	out := ui.NewWithColor(io.Discard, false)
+
+	require.NoError(t, writeConfigSet(out, configPath,
+		"age_recipients.0", identity.Recipient().String()))
+	require.NoError(t, writeConfigSet(out, configPath,
+		"age_secret_key", identity.String()))
+
+	return configPath, storeDir
+}
+
+// onlySnapshotID returns the ID of the one snapshot in the local index
+// that writeBackupConfig puts beside the config file.
+func onlySnapshotID(t *testing.T, configPath string) string {
+	t.Helper()
+
+	ctx := context.Background()
+
+	db, err := database.New(ctx,
+		filepath.Join(filepath.Dir(configPath), "index.sqlite"))
+	require.NoError(t, err)
+
+	defer func() { require.NoError(t, db.Close()) }()
+
+	backedUp, err := database.NewRepositories(db).Snapshots.GetOnlySnapshot(ctx)
+	require.NoError(t, err)
+
+	return backedUp.ID.String()
+}

internal/cli/entry_snapshot_create_index_and_lock_files_test.go

@@ -0,0 +1,69 @@
+package cli //nolint:testpackage // shares runEntry and the hermetic config helpers
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/adrg/xdg"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// TestEntrySnapshotCreateSkipsIndexAndLockFiles backs up a directory
+// that holds vaultik's index and PID file beside one other file, with no
+// exclude pattern set. The summary counts only the other file. See
+// https://git.eeqj.de/sneak/vaultik/issues/421.
+//
+// Not parallel: it replaces os.Args, os.Stdout, os.Stderr and the xdg
+// globals.
+func TestEntrySnapshotCreateSkipsIndexAndLockFiles(t *testing.T) {
+	for _, testCase := range []struct {
+		name string
+		// linked sets index_path to a symlink outside the backed-up
+		// directory that points to the index inside it.
+		linked bool
+	}{
+		{name: "index in the backed-up directory"},
+		{name: "index_path links into the backed-up directory", linked: true},
+	} {
+		t.Run(testCase.name, func(t *testing.T) {
+			dir := t.TempDir()
+			configPath := filepath.Join(dir, "config.yml")
+			sourceDir := filepath.Join(dir, "source")
+			storeDir := filepath.Join(dir, "store")
+
+			indexPath := filepath.Join(sourceDir, "index.sqlite")
+
+			if testCase.linked {
+				link := filepath.Join(dir, "index.sqlite")
+				require.NoError(t, os.Symlink(indexPath, link))
+
+				indexPath = link
+			}
+
+			contents := fmt.Sprintf(hermeticConfig,
+				sourceDir, storeDir, indexPath)
+			require.NoError(t,
+				os.WriteFile(configPath, []byte(contents), configFileMode))
+			require.NoError(t, os.Mkdir(storeDir, 0o750))
+			require.NoError(t, os.Mkdir(sourceDir, 0o750))
+			require.NoError(t, os.WriteFile(
+				filepath.Join(sourceDir, "file.txt"), []byte("hello"), 0o600))
+
+			// The PID file goes in a directory under XDG_DATA_HOME, which
+			// xdg reads at package init.
+			t.Setenv("XDG_DATA_HOME", filepath.Join(sourceDir, "data"))
+			xdg.Reload()
+			t.Cleanup(xdg.Reload)
+
+			code, stdout, _ := runEntry(t,
+				flagConfig, configPath, cmdSnapshot, cmdCreate)
+
+			require.Equal(t, 0, code)
+			assert.Contains(t, stdout,
+				"Files: 1 examined, 1 backed up, 0 unchanged.")
+		})
+	}
+}

internal/cli/entry_snapshot_create_prune_test.go

@@ -61,8 +61,8 @@ func TestEntrySnapshotCreateRejectsKeepNewerThanBeforeBackup(t *testing.T) {
 
 // TestEntrySnapshotCreateReportsPostBackupPruneFailure makes the
 // post-backup prune fail after a good backup, by planting a manifest
-// that cannot be decoded, and checks that the failure is reported as the
+// that cannot be decoded, and checks that the failure is reported once,
-// prune's and not as a failed snapshot creation.
+// as the prune's and not as a failed snapshot creation.
 //
 //nolint:paralleltest // replaces os.Args, os.Stdout, os.Stderr and the xdg globals
 func TestEntrySnapshotCreateReportsPostBackupPruneFailure(t *testing.T) {
@@ -83,6 +83,9 @@ func TestEntrySnapshotCreateReportsPostBackupPruneFailure(t *testing.T) {
 	assert.Contains(t, stderr, "Backup completed, but post-backup prune failed")
 	assert.NotContains(t, stderr, "Snapshot creation failed")
 
+	_, repeats := failureOutput(t, stderr)
+	assert.Zero(t, repeats, "no log record may repeat the error:\n%s", stderr)
+
 	snapshots, err := os.ReadDir(filepath.Join(storeDir, "metadata"))
 	require.NoError(t, err)
 	assert.Len(t, snapshots, 2,
@@ -93,7 +96,8 @@ func TestEntrySnapshotCreateReportsPostBackupPruneFailure(t *testing.T) {
 // empties the source directory, as a volume that is not mounted leaves
 // its mount point, and runs `snapshot create --prune`. The command exits
 // non-zero and reports the backup as completed, not as a failed snapshot
-// creation. See https://git.eeqj.de/sneak/vaultik/issues/388.
+// creation. The error is printed once. See
+// https://git.eeqj.de/sneak/vaultik/issues/388.
 //
 //nolint:paralleltest // replaces os.Args, os.Stdout, os.Stderr and the xdg globals
 func TestEntrySnapshotCreatePruneExitsNonZeroWhenSourceIsEmpty(t *testing.T) {
@@ -114,6 +118,9 @@ func TestEntrySnapshotCreatePruneExitsNonZeroWhenSourceIsEmpty(t *testing.T) {
 		"Backup completed, but 1 source path(s) were empty")
 	assert.NotContains(t, stderr, "Snapshot creation failed")
 
+	_, repeats := failureOutput(t, stderr)
+	assert.Zero(t, repeats, "no log record may repeat the error:\n%s", stderr)
+
 	snapshots, err := os.ReadDir(filepath.Join(storeDir, "metadata"))
 	require.NoError(t, err)
 	assert.Len(t, snapshots, 2, "the older snapshot is kept")
@@ -124,7 +131,8 @@ func TestEntrySnapshotCreatePruneExitsNonZeroWhenSourceIsEmpty(t *testing.T) {
 // directory as a mount point, and runs `snapshot create --prune`, which
 // does not find it as one. The command exits non-zero, reports the
 // backup as completed, not as a failed snapshot creation, and keeps the
-// older snapshot. See https://git.eeqj.de/sneak/vaultik/issues/395.
+// older snapshot. The error is printed once. See
+// https://git.eeqj.de/sneak/vaultik/issues/395.
 //
 //nolint:paralleltest // replaces os.Args, os.Stdout, os.Stderr and the xdg globals
 func TestEntrySnapshotCreatePruneExitsNonZeroWhenMountPointIsMissing(
@@ -159,6 +167,9 @@ func TestEntrySnapshotCreatePruneExitsNonZeroWhenMountPointIsMissing(
 		"an earlier snapshot recorded were not found")
 	assert.NotContains(t, stderr, "Snapshot creation failed")
 
+	_, repeats := failureOutput(t, stderr)
+	assert.Zero(t, repeats, "no log record may repeat the error:\n%s", stderr)
+
 	snapshots, err := os.ReadDir(filepath.Join(storeDir, "metadata"))
 	require.NoError(t, err)
 	assert.Len(t, snapshots, 2, "the older snapshot is kept")

internal/cli/info.go

@@ -39,7 +39,7 @@ func NewInfoCommand() *cobra.Command {
 			}, func(v *vaultik.Vaultik) error {
 				return v.ShowInfo()
 			}, func(err error) {
-				log.Error("Failed to show info", "error", err)
+				log.Info("Failed to show info", "error", err)
 				ReportErrorf("Failed to show info: %v", err)
 			})
 		},

internal/cli/prune.go

@@ -60,7 +60,7 @@ referenced.`,
 			}, func(v *vaultik.Vaultik) error {
 				return v.Prune(opts)
 			}, func(err error) {
-				log.Error("Prune operation failed", "error", err)
+				log.Info("Prune operation failed", "error", err)
 				ReportErrorf("Prune failed: %v", err)
 			})
 		},

internal/cli/remote.go

@@ -98,7 +98,7 @@ func newRemoteInfoCommand() *cobra.Command {
 			}, func(v *vaultik.Vaultik) error {
 				return v.RemoteInfo(jsonOutput)
 			}, func(err error) {
-				log.Error("Failed to get remote info", "error", err)
+				log.Info("Failed to get remote info", "error", err)
 				ReportErrorf("Failed to get remote info: %v", err)
 			})
 		},

internal/cli/snapshot.go

@@ -109,7 +109,7 @@ on Linux), then /etc/vaultik/config.yml.`,
 				return v.CreateSnapshot(opts)
 			}, func(err error) {
 				if errors.Is(err, vaultik.ErrPostBackupPruneFailed) {
-					log.Error("Post-backup prune failed", "error", err)
+					log.Info("Post-backup prune failed", "error", err)
 					ReportErrorf("Backup completed, but %v", err)
 
 					return
@@ -118,13 +118,13 @@ on Linux), then /etc/vaultik/config.yml.`,
 				if errors.Is(err, vaultik.ErrFilesUnreadable) ||
 					errors.Is(err, vaultik.ErrSourcePathEmpty) ||
 					errors.Is(err, vaultik.ErrVolumeNotMounted) {
-					log.Error("Backup completed with an error", "error", err)
+					log.Info("Backup completed with an error", "error", err)
 					ReportErrorf("Backup completed, but %v", err)
 
 					return
 				}
 
-				log.Error("Snapshot creation failed", "error", err)
+				log.Info("Snapshot creation failed", "error", err)
 				ReportErrorf("Snapshot creation failed: %v", err)
 			})
 		},
@@ -258,7 +258,7 @@ func newSnapshotVerifyCommand() *cobra.Command {
 					return
 				}
 
-				log.Error("Verification failed", "error", err)
+				log.Info("Verification failed", "error", err)
 				ReportErrorf("Verification failed: %v", err)
 			})
 		},

internal/cli/snapshot_restore.go

@@ -104,7 +104,7 @@ func runRestore(cmd *cobra.Command, args []string, opts *RestoreOptions) error {
 			SkipErrors: rootFlags.SkipErrors,
 		})
 	}, func(err error) {
-		log.Error("Restore operation failed", "error", err)
+		log.Info("Restore operation failed", "error", err)
 		ReportErrorf("Restore failed: %v", err)
 	})
 }

internal/config/config.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"reflect"
 	"sort"
 	"strings"
 	"time"
@@ -69,14 +70,22 @@ var (
 	errFileURLNotAbsolute = errors.New(
 		"a file:// storage_url needs an absolute path, " +
 			"as in file:///path/to/backup")
+	errIndexPathNotAbsolute = errors.New(
+		"index_path and VAULTIK_INDEX_PATH need an absolute path, " +
+			"as in ~/.local/share/vaultik/index.sqlite")
 	errNegativePruneGracePeriod = errors.New(
 		"prune_grace_period must not be negative")
 	errStorageNotConfigured = errors.New(
 		"storage not configured; set storage_url or provide s3.endpoint + " +
 			"s3.bucket + credentials")
 	errS3BucketRequired = errors.New("s3.bucket is required (or set storage_url)")
-	errS3KeyIDRequired  = errors.New("s3.access_key_id is required")
+)
-	errS3SecretRequired = errors.New("s3.secret_access_key is required")
+
+// Validate returns these when S3 storage is configured without its
+// credentials.
+var (
+	ErrS3KeyIDRequired  = errors.New("s3.access_key_id is required")
+	ErrS3SecretRequired = errors.New("s3.secret_access_key is required")
 )
 
 // expandTilde expands ~ at the start of a path to the user's home directory.
@@ -286,15 +295,39 @@ func Load(path string) (*Config, error) {
 }
 
 // Parse reads YAML config data as Load does, without validating it. It
-// applies default values for optional fields, fills in ${...} references
+// refuses a key that no setting has and a size setting whose value is not a
-// using smartconfig, and expands ~ in paths.
+// size, naming the setting. It applies default values for optional
+// fields, fills in ${...} references using smartconfig, and expands ~ in
+// paths.
 func Parse(data []byte) (*Config, error) {
+	// smartconfig drops line numbers, so keys are checked in the data as
+	// written.
+	var root yaml.Node
+
+	err := yaml.Unmarshal(data, &root)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse config: %w", err)
+	}
+
+	err = checkKeys(&root, reflect.TypeFor[Config](), "",
+		map[*yaml.Node]bool{}, map[nodeAndType]bool{})
+	if err != nil {
+		return nil, err
+	}
+
 	// Load config using smartconfig for interpolation
 	sc, err := smartconfig.NewFromReader(bytes.NewReader(data))
 	if err != nil {
 		return nil, fmt.Errorf("failed to load config file: %w", err)
 	}
 
+	// A ${...} reference can bring in keys that are not in the file, and
+	// is the value of a size setting only once it is filled in.
+	err = checkFilledConfig(sc.Data())
+	if err != nil {
+		return nil, err
+	}
+
 	cfg := &Config{
 		// Set defaults
 		BlobSizeLimit:    defaultBlobSizeLimit,
@@ -363,7 +396,11 @@ func Parse(data []byte) (*Config, error) {
 //     never the value. An empty list is accepted, because only snapshot
 //     create needs a recipient and it checks for one itself
 //   - At least one snapshot must be configured with at least one path
+//   - Every exclude pattern, global or in a snapshot, must compile; errors
+//     name the setting and quote the pattern
 //   - Storage must be configured (either storage_url or s3.* fields)
+//   - The index path must be absolute: a relative one would resolve against
+//     the working directory, so each directory would get its own index
 //   - Chunk size must be at least 1MB
 //   - Blob size limit must be at least the largest chunk the chunker can emit
 //     (chunk_size times chunker.ChunkSizeSpread), so a single-chunk blob never
@@ -381,22 +418,26 @@ func (c *Config) Validate() error {
 		}
 	}
 
-	if len(c.Snapshots) == 0 {
+	err := c.validateSnapshots()
-		return errNoSnapshots
+	if err != nil {
+		return err
 	}
 
-	for name, snap := range c.Snapshots {
+	err = c.validateExcludes()
-		if len(snap.Paths) == 0 {
+	if err != nil {
-			return fmt.Errorf("%w: %q", errSnapshotNoPaths, name)
+		return err
-		}
 	}
 
 	// Validate storage configuration
-	err := c.validateStorage()
+	err = c.validateStorage()
 	if err != nil {
 		return err
 	}
 
+	if !filepath.IsAbs(c.IndexPath) {
+		return fmt.Errorf("%w: %q", errIndexPathNotAbsolute, c.IndexPath)
+	}
+
 	if c.ChunkSize.Int64() < minChunkSize {
 		return errChunkSizeTooSmall
 	}
@@ -427,6 +468,22 @@ func (c *Config) Validate() error {
 	return nil
 }
 
+// validateSnapshots refuses a config with no snapshot or with a snapshot
+// that has no path.
+func (c *Config) validateSnapshots() error {
+	if len(c.Snapshots) == 0 {
+		return errNoSnapshots
+	}
+
+	for name, snap := range c.Snapshots {
+		if len(snap.Paths) == 0 {
+			return fmt.Errorf("%w: %q", errSnapshotNoPaths, name)
+		}
+	}
+
+	return nil
+}
+
 // validateAgeRecipient parses one age_recipients entry with the age library
 // and returns a value-free error on failure. A recipient string can be
 // sensitive (an operator may paste a secret key by mistake), so neither the
@@ -490,11 +547,11 @@ func (c *Config) validateStorage() error {
 	}
 
 	if c.S3.AccessKeyID == "" {
-		return errS3KeyIDRequired
+		return ErrS3KeyIDRequired
 	}
 
 	if c.S3.SecretAccessKey == "" {
-		return errS3SecretRequired
+		return ErrS3SecretRequired
 	}
 
 	return nil
@@ -521,11 +578,11 @@ func (c *Config) validateStorageURL() error {
 	case strings.HasPrefix(c.StorageURL, "s3://"):
 		// S3 storage needs credentials
 		if c.S3.AccessKeyID == "" {
-			return fmt.Errorf("%w for s3:// URLs", errS3KeyIDRequired)
+			return fmt.Errorf("%w for s3:// URLs", ErrS3KeyIDRequired)
 		}
 
 		if c.S3.SecretAccessKey == "" {
-			return fmt.Errorf("%w for s3:// URLs", errS3SecretRequired)
+			return fmt.Errorf("%w for s3:// URLs", ErrS3SecretRequired)
 		}
 
 		return nil

internal/config/config_test.go

@@ -165,6 +165,7 @@ func TestValidateBlobSizeLimit(t *testing.T) {
 			AgeRecipients:    []string{testSneakAgePublicKey},
 			Snapshots:        map[string]SnapshotConfig{"test": {Paths: []string{"/tmp/src"}}},
 			StorageURL:       "file:///tmp/vaultik-test-store",
+			IndexPath:        "/tmp/vaultik-test-index.sqlite",
 			ChunkSize:        chunkSize,
 			BlobSizeLimit:    blobLimit,
 			CompressionLevel: 3,
@@ -510,6 +511,65 @@ func TestLoadRejectsRelativeFileURL(t *testing.T) {
 	}
 }
 
+// TestLoadIndexPath checks that a relative index_path fails at load, naming
+// the value. Accepted, it would resolve against the working directory, so a
+// backup run from another directory would start from an empty index. A path
+// starting with ~ is expanded and loads.
+func TestLoadIndexPath(t *testing.T) {
+	t.Parallel()
+
+	home, err := os.UserHomeDir()
+	if err != nil {
+		t.Fatalf("home directory: %v", err)
+	}
+
+	load := func(t *testing.T, indexPath string) (*Config, error) {
+		t.Helper()
+
+		data := "snapshots:\n" +
+			"  test:\n" +
+			"    paths: [/tmp/vaultik-test-source]\n" +
+			"storage_url: file:///tmp/vaultik-test-storage\n" +
+			"index_path: " + indexPath + "\n"
+
+		path := filepath.Join(t.TempDir(), "config.yml")
+
+		err := os.WriteFile(path, []byte(data), 0o600)
+		if err != nil {
+			t.Fatalf("write config: %v", err)
+		}
+
+		return Load(path)
+	}
+
+	t.Run("relative path is rejected", func(t *testing.T) {
+		t.Parallel()
+
+		_, err := load(t, "relative/index.sqlite")
+		if !errors.Is(err, errIndexPathNotAbsolute) {
+			t.Fatalf("Load() error = %v, want errIndexPathNotAbsolute", err)
+		}
+
+		if !strings.Contains(err.Error(), `"relative/index.sqlite"`) {
+			t.Errorf("error %q does not name the value", err.Error())
+		}
+	})
+
+	t.Run("path starting with ~ is expanded", func(t *testing.T) {
+		t.Parallel()
+
+		cfg, err := load(t, "~/vaultik/index.sqlite")
+		if err != nil {
+			t.Fatalf("Load() unexpected error: %v", err)
+		}
+
+		want := filepath.Join(home, "vaultik", "index.sqlite")
+		if cfg.IndexPath != want {
+			t.Errorf("IndexPath = %q, want %q", cfg.IndexPath, want)
+		}
+	})
+}
+
 // TestValidateAgeRecipients checks that recipients are parsed at config load
 // (a bad entry fails immediately, not mid-backup) and that no invalid entry —
 // least of all a pasted secret key — is echoed in the error. An empty list
@@ -522,6 +582,7 @@ func TestValidateAgeRecipients(t *testing.T) {
 			AgeRecipients:    recipients,
 			Snapshots:        map[string]SnapshotConfig{"test": {Paths: []string{"/tmp/src"}}},
 			StorageURL:       "file:///tmp/vaultik-test-store",
+			IndexPath:        "/tmp/vaultik-test-index.sqlite",
 			ChunkSize:        Size(10 * 1024 * 1024),
 			BlobSizeLimit:    Size(10 * 1024 * 1024 * 1024),
 			CompressionLevel: 3,

internal/config/exclude.go

@@ -0,0 +1,39 @@
+package config
+
+import (
+	"fmt"
+
+	"sneak.berlin/go/vaultik/internal/exclude"
+)
+
+// validateExcludes refuses an exclude pattern, global or in a snapshot,
+// that does not compile, naming the setting and quoting the pattern.
+func (c *Config) validateExcludes() error {
+	err := validateExcludeList("exclude", c.Exclude)
+	if err != nil {
+		return err
+	}
+
+	for _, name := range c.SnapshotNames() {
+		err = validateExcludeList("snapshots."+name+".exclude",
+			c.Snapshots[name].Exclude)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// validateExcludeList refuses the first pattern in patterns that does not
+// compile. setting is the name of the list, as in "exclude".
+func validateExcludeList(setting string, patterns []string) error {
+	for i, pattern := range patterns {
+		_, _, err := exclude.Compile(pattern)
+		if err != nil {
+			return fmt.Errorf("%s[%d]: %w", setting, i, err)
+		}
+	}
+
+	return nil
+}

internal/config/exclude_test.go

@@ -0,0 +1,65 @@
+package config_test
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"sneak.berlin/go/vaultik/internal/config"
+)
+
+// TestLoadRefusesBadExcludePattern checks that an exclude pattern that does
+// not compile, global or in a snapshot, fails at load with the setting and
+// the pattern named, rather than the backup storing what it meant to leave
+// out.
+func TestLoadRefusesBadExcludePattern(t *testing.T) {
+	t.Parallel()
+
+	const storage = "storage_url: file:///tmp/vaultik-test-storage\n"
+
+	tests := []struct {
+		name    string
+		config  string
+		wantErr string
+	}{
+		{
+			name: "global",
+			config: "exclude: ['*.tmp', '.cache', 'build[']\n" +
+				"snapshots:\n" +
+				"  home:\n" +
+				"    paths: [/tmp/vaultik-test-source]\n" + storage,
+			wantErr: `exclude[2]: "build[" is not a valid exclude pattern`,
+		},
+		{
+			name: "snapshot",
+			config: "snapshots:\n" +
+				"  home:\n" +
+				"    paths: [/tmp/vaultik-test-source]\n" +
+				"    exclude: ['/a/**/x[']\n" + storage,
+			wantErr: `snapshots.home.exclude[0]: "/a/**/x[" is not a valid exclude pattern`,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			path := filepath.Join(t.TempDir(), "config.yml")
+
+			err := os.WriteFile(path, []byte(tt.config), 0o600)
+			if err != nil {
+				t.Fatalf("write config: %v", err)
+			}
+
+			_, err = config.Load(path)
+			if err == nil {
+				t.Fatalf("Load() returned nil, want an error containing %q", tt.wantErr)
+			}
+
+			if !strings.Contains(err.Error(), tt.wantErr) {
+				t.Fatalf("Load() error = %q, want it to contain %q", err, tt.wantErr)
+			}
+		})
+	}
+}

internal/config/keys.go

@@ -0,0 +1,220 @@
+package config
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+
+	"gopkg.in/yaml.v3"
+)
+
+// yamlMergeTag is the tag YAML gives a merge key (<<), which adds the keys
+// of the map it names to the map it sits in.
+const yamlMergeTag = "!!merge"
+
+// EnvSection is the top-level key of a map of environment variables that
+// smartconfig sets while it loads the config. It is not a vaultik setting,
+// so its keys are not checked.
+const EnvSection = "env"
+
+var (
+	errUnknownKey           = errors.New("unknown config key")
+	errAnchorContainsItself = errors.New("anchor contains itself")
+)
+
+// nodeAndType is a node of a parsed config and the setting type it is
+// checked against.
+type nodeAndType struct {
+	node *yaml.Node
+	typ  reflect.Type
+}
+
+// SettingType returns the type of the setting that the dotted key names in
+// Config, following the fields' yaml tags, as for s3.bucket or
+// snapshots.home.exclude.0. A snapshot name or a list index may be any
+// word. It returns an unknown key error when no setting has that key.
+func SettingType(keys []string) (reflect.Type, error) {
+	typ := reflect.TypeFor[Config]()
+
+	for _, key := range keys {
+		switch {
+		case typ.Kind() == reflect.Map || typ.Kind() == reflect.Slice:
+			typ = typ.Elem()
+		case typ.Kind() == reflect.Struct:
+			field, ok := yamlField(typ, key)
+			if !ok {
+				return nil, fmt.Errorf("%w %q", errUnknownKey, strings.Join(keys, "."))
+			}
+
+			typ = field.Type
+		default:
+			return nil, fmt.Errorf("%w %q", errUnknownKey, strings.Join(keys, "."))
+		}
+	}
+
+	return typ, nil
+}
+
+// yamlField returns the field of struct type typ whose yaml tag names key.
+func yamlField(typ reflect.Type, key string) (reflect.StructField, bool) {
+	for field := range typ.Fields() {
+		name, _, _ := strings.Cut(field.Tag.Get("yaml"), ",")
+		if name == key && name != "-" {
+			return field, true
+		}
+	}
+
+	return reflect.StructField{}, false
+}
+
+// checkKeys returns an error naming the first key in node, a parsed config
+// or part of one at the dotted path, that no setting in typ has. The error
+// gives the key's line in the file, when it has one. A value of the wrong
+// type is left for the YAML decoder to report. following holds the aliases
+// the walk is inside. Meeting one of them again means its anchor contains
+// itself, which is an error. checked holds each anchored node the walk has
+// checked completely, with the type it was checked against. An alias to
+// that node is not followed again for that type.
+func checkKeys(node *yaml.Node, typ reflect.Type, path string,
+	following map[*yaml.Node]bool, checked map[nodeAndType]bool,
+) error {
+	switch node.Kind {
+	case yaml.DocumentNode:
+		for _, child := range node.Content {
+			err := checkKeys(child, typ, path, following, checked)
+			if err != nil {
+				return err
+			}
+		}
+	case yaml.AliasNode:
+		if following[node] {
+			return fmt.Errorf("%w: %q on line %d",
+				errAnchorContainsItself, node.Value, node.Line)
+		}
+
+		target := nodeAndType{node.Alias, typ}
+		if checked[target] {
+			return nil
+		}
+
+		following[node] = true
+		defer delete(following, node)
+
+		err := checkKeys(node.Alias, typ, path, following, checked)
+		if err != nil {
+			return err
+		}
+
+		checked[target] = true
+	case yaml.SequenceNode:
+		if typ.Kind() != reflect.Slice {
+			return nil
+		}
+
+		for i, child := range node.Content {
+			err := checkKeys(child, typ.Elem(), joinKey(path, strconv.Itoa(i)),
+				following, checked)
+			if err != nil {
+				return err
+			}
+		}
+	case yaml.MappingNode:
+		return checkMappingKeys(node, typ, path, following, checked)
+	case yaml.ScalarNode:
+		// A scalar has no keys.
+	}
+
+	return nil
+}
+
+// checkFilledConfig checks data, the config after smartconfig has filled in
+// its ${...} references: its keys with checkKeys, then its size settings
+// with checkSizes. A key that a reference brings in is not in the file, and
+// the copy that Encode makes has no line numbers.
+func checkFilledConfig(data map[string]any) error {
+	var filled yaml.Node
+
+	err := filled.Encode(data)
+	if err != nil {
+		return fmt.Errorf("failed to marshal config data: %w", err)
+	}
+
+	err = checkKeys(&filled, reflect.TypeFor[Config](), "",
+		map[*yaml.Node]bool{}, map[nodeAndType]bool{})
+	if err != nil {
+		return err
+	}
+
+	return checkSizes(&filled, nil)
+}
+
+// checkMappingKeys is checkKeys for a map.
+func checkMappingKeys(node *yaml.Node, typ reflect.Type, path string,
+	following map[*yaml.Node]bool, checked map[nodeAndType]bool,
+) error {
+	for i := 0; i+1 < len(node.Content); i += 2 {
+		key, value := node.Content[i], node.Content[i+1]
+
+		if key.Tag == yamlMergeTag {
+			// The value is one map or a list of maps.
+			merged := []*yaml.Node{value}
+			if value.Kind == yaml.SequenceNode {
+				merged = value.Content
+			}
+
+			for _, m := range merged {
+				err := checkKeys(m, typ, path, following, checked)
+				if err != nil {
+					return err
+				}
+			}
+
+			continue
+		}
+
+		keyPath := joinKey(path, key.Value)
+		if keyPath == EnvSection {
+			continue
+		}
+
+		var valueType reflect.Type
+
+		switch {
+		case typ.Kind() == reflect.Map:
+			valueType = typ.Elem()
+		case typ.Kind() == reflect.Struct:
+			field, ok := yamlField(typ, key.Value)
+			if !ok && key.Line == 0 {
+				// A key that a ${...} reference brought in has no line.
+				return fmt.Errorf("%w %q", errUnknownKey, keyPath)
+			}
+
+			if !ok {
+				return fmt.Errorf("%w %q on line %d",
+					errUnknownKey, keyPath, key.Line)
+			}
+
+			valueType = field.Type
+		default:
+			return nil
+		}
+
+		err := checkKeys(value, valueType, keyPath, following, checked)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// joinKey appends key to the dotted path.
+func joinKey(path, key string) string {
+	if path == "" {
+		return key
+	}
+
+	return path + "." + key
+}

internal/config/keys_test.go

@@ -0,0 +1,163 @@
+package config //nolint:testpackage // checks the unexported errUnknownKey
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"slices"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+// keysTestConfig loads; each case below adds one line to it.
+const keysTestConfig = "storage_url: file:///tmp/vaultik-test-storage\n" +
+	"s3:\n" +
+	"  region: us-east-1\n" +
+	"snapshots:\n" +
+	"  test:\n" +
+	"    paths: [/tmp/vaultik-test-source]\n"
+
+// TestParseRefusesUnknownKey checks that a key no setting has, at any
+// depth, fails the parse with an error naming the key and its line. A key
+// that a ${...} reference brings in is not in the file, so its error gives
+// no line.
+func TestParseRefusesUnknownKey(t *testing.T) {
+	t.Parallel()
+
+	snapshotPath := filepath.Join(t.TempDir(), "snapshot.yml")
+
+	err := os.WriteFile(snapshotPath, []byte("other:\n"+
+		"  paths: [/tmp/vaultik-test-source]\n"+
+		"  exlude: [/tmp/cache]\n"), 0o600)
+	if err != nil {
+		t.Fatalf("write snapshot: %v", err)
+	}
+
+	tests := []struct {
+		name string
+		yaml string
+		want string
+	}{
+		{"top level", keysTestConfig + "compression_lvl: 9\n",
+			`unknown config key "compression_lvl" on line 7`},
+		{"in a snapshot", keysTestConfig + "    exlude: [/tmp/cache]\n",
+			`unknown config key "snapshots.test.exlude" on line 7`},
+		{"in s3", strings.Replace(keysTestConfig, "  region:",
+			"  bukcet: b\n  region:", 1),
+			`unknown config key "s3.bukcet" on line 3`},
+		{"from a reference",
+			keysTestConfig + "  other: ${YAML:" + snapshotPath + ":other}\n",
+			`unknown config key "snapshots.other.exlude"`},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			_, err := Parse([]byte(tt.yaml))
+			if !errors.Is(err, errUnknownKey) {
+				t.Fatalf("Parse() error = %v, want errUnknownKey", err)
+			}
+
+			if err.Error() != tt.want {
+				t.Errorf("Parse() error = %q, want %q", err.Error(), tt.want)
+			}
+		})
+	}
+}
+
+// TestParseRefusesAnchorThatContainsItself checks that a YAML merge key (<<)
+// naming the anchor of the map it sits in fails the parse with an error.
+func TestParseRefusesAnchorThatContainsItself(t *testing.T) {
+	t.Parallel()
+
+	data := strings.Replace(keysTestConfig, "  test:", "  test: &test", 1) +
+		"    <<: *test\n"
+
+	_, err := Parse([]byte(data))
+	if !errors.Is(err, errAnchorContainsItself) {
+		t.Fatalf("Parse() error = %v, want errAnchorContainsItself", err)
+	}
+
+	want := `anchor contains itself: "test" on line 7`
+	if err.Error() != want {
+		t.Errorf("Parse() error = %q, want %q", err.Error(), want)
+	}
+}
+
+// TestParseRefusesExcessiveAliasing checks that Parse returns an error for
+// a file whose merge keys (<<) fan out. Each of eight snapshots merges the
+// one before it ten times. A key check that followed every alias would walk
+// the first snapshot over 10^8 times and run past the package's test
+// timeout.
+func TestParseRefusesExcessiveAliasing(t *testing.T) {
+	t.Parallel()
+
+	const snapshots, merges = 8, 10
+
+	var data strings.Builder
+
+	data.WriteString(strings.Replace(keysTestConfig, "  test:", "  test: &s0", 1))
+
+	for i := 1; i <= snapshots; i++ {
+		aliases := slices.Repeat([]string{"*s" + strconv.Itoa(i-1)}, merges)
+		fmt.Fprintf(&data, "  s%d: &s%d\n    <<: [%s]\n",
+			i, i, strings.Join(aliases, ", "))
+	}
+
+	_, err := Parse([]byte(data.String()))
+	if err == nil {
+		t.Fatal("Parse() returned no error")
+	}
+}
+
+// TestParseAcceptsKnownKeys checks that a config with a ${...} reference
+// and a YAML merge key (<<) still parses.
+func TestParseAcceptsKnownKeys(t *testing.T) {
+	t.Parallel()
+
+	levelPath := filepath.Join(t.TempDir(), "level")
+
+	err := os.WriteFile(levelPath, []byte("9"), 0o600)
+	if err != nil {
+		t.Fatalf("write level: %v", err)
+	}
+
+	data := strings.Replace(keysTestConfig, "  test:", "  test: &test", 1) +
+		"  other:\n" +
+		"    <<: *test\n" +
+		"    exclude: [/tmp/vaultik-test-source/cache]\n" +
+		"compression_level: ${FILE:" + levelPath + "}\n"
+
+	cfg, err := Parse([]byte(data))
+	if err != nil {
+		t.Fatalf("Parse() unexpected error: %v", err)
+	}
+
+	if cfg.CompressionLevel != 9 {
+		t.Errorf("compression_level = %d, want 9", cfg.CompressionLevel)
+	}
+
+	other := cfg.Snapshots["other"]
+	if len(other.Paths) != 1 || len(other.Exclude) != 1 {
+		t.Errorf("snapshot other = %+v, want the paths of test and one exclude",
+			other)
+	}
+}
+
+// TestParseAcceptsEnvSection checks that a config with a top-level env
+// section still parses. smartconfig sets the environment variables it
+// lists, so its keys are not settings.
+func TestParseAcceptsEnvSection(t *testing.T) {
+	const name = "VAULTIK_TEST_ENV_SECTION"
+
+	// Parse sets the variable; t.Setenv restores it after the test.
+	t.Setenv(name, "")
+
+	_, err := Parse([]byte(keysTestConfig + "env:\n  " + name + ": set\n"))
+	if err != nil {
+		t.Fatalf("Parse() unexpected error: %v", err)
+	}
+}

internal/config/size.go

@@ -4,13 +4,20 @@ import (
 	"errors"
 	"fmt"
 	"math"
+	"reflect"
+	"slices"
+	"strconv"
+	"strings"
 
 	"github.com/dustin/go-humanize"
+	"gopkg.in/yaml.v3"
 )
 
 var (
 	errSizeType     = errors.New("size must be a number or string")
 	errSizeTooLarge = errors.New("size exceeds maximum supported value")
+	errNotASize     = errors.New(
+		"is not a size; use a number of bytes or a unit such as 10MB")
 )
 
 // Size represents a byte size that can be specified in configuration files.
@@ -32,6 +39,15 @@ func (s *Size) UnmarshalYAML(unmarshal func(any) error) error {
 		return nil
 	}
 
+	// A number too large for an int64 decodes as a float64. Its text can be
+	// 1e+20, which is not a size string.
+	var floatVal float64
+
+	err = unmarshal(&floatVal)
+	if err == nil && floatVal > math.MaxInt64 {
+		return errSizeTooLarge
+	}
+
 	// Try to unmarshal as string
 	var strVal string
 
@@ -40,17 +56,66 @@ func (s *Size) UnmarshalYAML(unmarshal func(any) error) error {
 		return errSizeType
 	}
 
-	// Parse the string using go-humanize
+	size, err := ParseSize(strVal)
-	bytes, err := humanize.ParseBytes(strVal)
 	if err != nil {
-		return fmt.Errorf("invalid size format: %w", err)
+		return err
 	}
 
-	if bytes > math.MaxInt64 {
+	*s = size
-		return fmt.Errorf("%w: %s", errSizeTooLarge, strVal)
+
+	return nil
 }
 
-	*s = Size(bytes)
+// checkSizes returns an error naming the first size setting in node whose
+// value is not a size. node is the config, or the part of it at the dotted
+// keys, after smartconfig has filled in its ${...} references.
+func checkSizes(node *yaml.Node, keys []string) error {
+	typ, err := SettingType(keys)
+	if err != nil {
+		// Unknown keys are refused before this check, so keys is in one of
+		// two places. The env section holds no settings. A value of the
+		// wrong shape, such as a map given for hostname or inside exclude,
+		// is reported later by the YAML decoder.
+		return nil //nolint:nilerr // not an error here
+	}
+
+	if typ == reflect.TypeFor[Size]() {
+		var size Size
+
+		err = node.Decode(&size)
+		if err != nil {
+			return fmt.Errorf("%s: %w", strings.Join(keys, "."), err)
+		}
+
+		return nil
+	}
+
+	switch node.Kind {
+	case yaml.DocumentNode:
+		for _, child := range node.Content {
+			err = checkSizes(child, keys)
+			if err != nil {
+				return err
+			}
+		}
+	case yaml.MappingNode:
+		for i := 0; i+1 < len(node.Content); i += 2 {
+			err = checkSizes(node.Content[i+1],
+				slices.Concat(keys, []string{node.Content[i].Value}))
+			if err != nil {
+				return err
+			}
+		}
+	case yaml.SequenceNode:
+		for i, child := range node.Content {
+			err = checkSizes(child, slices.Concat(keys, []string{strconv.Itoa(i)}))
+			if err != nil {
+				return err
+			}
+		}
+	case yaml.ScalarNode, yaml.AliasNode:
+		// A scalar holds no settings, and the filled config has no aliases.
+	}
 
 	return nil
 }
@@ -70,16 +135,17 @@ func (s Size) String() string {
 	return humanize.Bytes(uint64(s))
 }
 
-// ParseSize parses a size string into a Size value
+// ParseSize parses a size string, such as "10MB", into a Size value. An
+// error quotes s.
 func ParseSize(s string) (Size, error) {
-	bytes, err := humanize.ParseBytes(s)
+	bytes, err := humanize.ParseBigBytes(s)
 	if err != nil {
-		return 0, fmt.Errorf("invalid size format: %w", err)
+		return 0, fmt.Errorf("%q %w", s, errNotASize)
 	}
 
-	if bytes > math.MaxInt64 {
+	if !bytes.IsInt64() {
 		return 0, fmt.Errorf("%w: %s", errSizeTooLarge, s)
 	}
 
-	return Size(bytes), nil
+	return Size(bytes.Int64()), nil
 }

internal/config/size_test.go

@@ -0,0 +1,120 @@
+package config //nolint:testpackage // checks errNotASize and errSizeTooLarge
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// TestParseRefusesValueThatIsNotASize checks that a size setting whose
+// value is not a size fails the parse with an error naming the setting and
+// quoting the value, also when a ${...} reference fills the value in.
+func TestParseRefusesValueThatIsNotASize(t *testing.T) {
+	t.Parallel()
+
+	sizePath := filepath.Join(t.TempDir(), "size")
+
+	err := os.WriteFile(sizePath, []byte("lots"), 0o600)
+	if err != nil {
+		t.Fatalf("write size: %v", err)
+	}
+
+	tests := []struct {
+		name string
+		yaml string
+		want string
+	}{
+		{"chunk_size", keysTestConfig + "chunk_size: banana\n",
+			`chunk_size: "banana" is not a size; ` +
+				"use a number of bytes or a unit such as 10MB"},
+		{"blob_size_limit", keysTestConfig + "blob_size_limit: 10XB\n",
+			`blob_size_limit: "10XB" is not a size; ` +
+				"use a number of bytes or a unit such as 10MB"},
+		{"s3.part_size", strings.Replace(keysTestConfig, "  region:",
+			"  part_size: big\n  region:", 1),
+			`s3.part_size: "big" is not a size; ` +
+				"use a number of bytes or a unit such as 10MB"},
+		{"from a reference",
+			keysTestConfig + "chunk_size: ${FILE:" + sizePath + "}\n",
+			`chunk_size: "lots" is not a size; ` +
+				"use a number of bytes or a unit such as 10MB"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			_, err := Parse([]byte(tt.yaml))
+			if !errors.Is(err, errNotASize) {
+				t.Fatalf("Parse() error = %v, want errNotASize", err)
+			}
+
+			if err.Error() != tt.want {
+				t.Errorf("Parse() error = %q, want %q", err.Error(), tt.want)
+			}
+		})
+	}
+}
+
+// TestParseRefusesSizeTooLarge checks that a size setting whose value is
+// too large for a size fails the parse with an error naming the setting.
+// YAML reads the second value as a float.
+func TestParseRefusesSizeTooLarge(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		value string
+		want  string
+	}{
+		{"100EB", "chunk_size: size exceeds maximum supported value: 100EB"},
+		{"99999999999999999999",
+			"chunk_size: size exceeds maximum supported value"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.value, func(t *testing.T) {
+			t.Parallel()
+
+			_, err := Parse([]byte(keysTestConfig + "chunk_size: " + tt.value + "\n"))
+			if !errors.Is(err, errSizeTooLarge) {
+				t.Fatalf("Parse() error = %v, want errSizeTooLarge", err)
+			}
+
+			if err.Error() != tt.want {
+				t.Errorf("Parse() error = %q, want %q", err.Error(), tt.want)
+			}
+		})
+	}
+}
+
+// TestParseAcceptsSizes checks that size settings given as a number of
+// bytes, as a unit, and through a ${...} reference still parse.
+func TestParseAcceptsSizes(t *testing.T) {
+	t.Parallel()
+
+	sizePath := filepath.Join(t.TempDir(), "size")
+
+	err := os.WriteFile(sizePath, []byte("20MB"), 0o600)
+	if err != nil {
+		t.Fatalf("write size: %v", err)
+	}
+
+	data := strings.Replace(keysTestConfig, "  region:",
+		"  part_size: 6000000\n  region:", 1) +
+		"chunk_size: ${FILE:" + sizePath + "}\n" +
+		"blob_size_limit: 1GB\n"
+
+	cfg, err := Parse([]byte(data))
+	if err != nil {
+		t.Fatalf("Parse() unexpected error: %v", err)
+	}
+
+	if cfg.ChunkSize != 20_000_000 || cfg.BlobSizeLimit != 1_000_000_000 ||
+		cfg.S3.PartSize != 6_000_000 {
+		t.Errorf("chunk_size, blob_size_limit, s3.part_size = %d, %d, %d, "+
+			"want 20000000, 1000000000, 6000000",
+			cfg.ChunkSize, cfg.BlobSizeLimit, cfg.S3.PartSize)
+	}
+}

internal/database/module.go

@@ -20,6 +20,17 @@ const indexDirPerm = 0o700
 // backed-up path and chunk hash and must stay private.
 const indexFilePerm = 0o600
 
+// IndexFiles returns the path of the index at indexPath and the paths of
+// the side files SQLite keeps beside it while it writes.
+func IndexFiles(indexPath string) []string {
+	return []string{
+		indexPath,
+		indexPath + "-wal",
+		indexPath + "-shm",
+		indexPath + "-journal",
+	}
+}
+
 // ensureIndexFileMode makes the index file owner-only before the SQLite
 // driver opens it: it creates the file 0600 if absent, or chmods an existing
 // one to 0600. Doing this first matters because SQLite creates its -wal and

internal/exclude/exclude.go

@@ -0,0 +1,77 @@
+// Package exclude compiles exclude patterns into globs.
+package exclude
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/gobwas/glob"
+)
+
+var errBadExcludePattern = errors.New("is not a valid exclude pattern")
+
+// Compile compiles one exclude pattern into the globs that match it.
+// anchored reports whether the pattern matches only from the root of the
+// source directory. An empty pattern yields no globs. Config.Validate and
+// the scanner both compile patterns with it, so a pattern that loads is one
+// the scanner can use.
+func Compile(pattern string) ([]glob.Glob, bool, error) {
+	if pattern == "" {
+		return nil, false, nil
+	}
+
+	// A leading "/" anchors the pattern to the source directory.
+	trimmed, anchored := strings.CutPrefix(pattern, "/")
+
+	// A trailing "/" marks a directory and is not matched.
+	trimmed = strings.TrimSuffix(trimmed, "/")
+
+	// A leading "**/" demands a "/" before the name and so misses an
+	// entry directly under the source path. It means "at every depth",
+	// which is what an unanchored pattern already does, so drop the
+	// prefix and match unanchored: as in gitignore, "**/x" and
+	// "/**/x" then also match a top-level "x".
+	if rest, found := strings.CutPrefix(trimmed, "**/"); found {
+		trimmed = rest
+		anchored = false
+	}
+
+	// Likewise "/**/" inside a pattern demands two slashes, so
+	// "a/**/*.log" misses "a/x.log". As in gitignore it stands for
+	// zero or more directories, so also compile the pattern with it
+	// made a single "/". The glob library's {a,b} is no help: with a
+	// "**" inside it in mid-pattern, it misses paths it should match.
+	var globs []glob.Glob
+
+	for _, variant := range doubleStarVariants(trimmed) {
+		g, err := glob.Compile(variant, '/')
+		if err != nil {
+			return nil, false, fmt.Errorf("%q %w: %w",
+				pattern, errBadExcludePattern, err)
+		}
+
+		globs = append(globs, g)
+	}
+
+	return globs, anchored, nil
+}
+
+// doubleStarVariants returns pattern once for every way of keeping each
+// "/**/" in it or making it a single "/".
+func doubleStarVariants(pattern string) []string {
+	const doubleStar = "/**/"
+
+	before, after, found := strings.Cut(pattern, doubleStar)
+	if !found {
+		return []string{pattern}
+	}
+
+	var variants []string
+
+	for _, rest := range doubleStarVariants(after) {
+		variants = append(variants, before+doubleStar+rest, before+"/"+rest)
+	}
+
+	return variants
+}

internal/exclude/exclude_test.go

@@ -0,0 +1,73 @@
+package exclude_test
+
+import (
+	"slices"
+	"strings"
+	"testing"
+
+	"github.com/gobwas/glob"
+	"sneak.berlin/go/vaultik/internal/exclude"
+)
+
+// TestCompile checks the error, the anchoring and the globs that Compile
+// returns for one exclude pattern.
+func TestCompile(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name         string
+		pattern      string
+		wantErr      string
+		wantAnchored bool
+		// wantMatches lists paths that one of the globs must match. When
+		// it is empty, Compile must return no globs.
+		wantMatches []string
+	}{
+		{name: "does not compile", pattern: "build[",
+			wantErr: `"build[" is not a valid exclude pattern`},
+		{name: "empty", pattern: ""},
+		{name: "leading slash anchors", pattern: "/build",
+			wantAnchored: true, wantMatches: []string{"build"}},
+		{name: "double star after the slash clears anchoring",
+			pattern: "/**/build", wantMatches: []string{"build"}},
+		{name: "double star in the middle", pattern: "a/**/*.log",
+			wantMatches: []string{"a/x.log", "a/b/x.log"}},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			globs, anchored, err := exclude.Compile(tt.pattern)
+			if tt.wantErr == "" && err != nil {
+				t.Fatalf("Compile(%q) error = %v, want none", tt.pattern, err)
+			}
+
+			if tt.wantErr != "" &&
+				(err == nil || !strings.HasPrefix(err.Error(), tt.wantErr)) {
+				t.Fatalf("Compile(%q) error = %v, want one starting with %q",
+					tt.pattern, err, tt.wantErr)
+			}
+
+			if anchored != tt.wantAnchored {
+				t.Errorf("Compile(%q) anchored = %t, want %t",
+					tt.pattern, anchored, tt.wantAnchored)
+			}
+
+			if len(tt.wantMatches) == 0 && len(globs) != 0 {
+				t.Errorf("Compile(%q) returned %d globs, want none",
+					tt.pattern, len(globs))
+			}
+
+			for _, path := range tt.wantMatches {
+				matched := slices.ContainsFunc(globs, func(g glob.Glob) bool {
+					return g.Match(path)
+				})
+				if !matched {
+					t.Errorf("Compile(%q) globs do not match %q",
+						tt.pattern, path)
+				}
+			}
+		})
+	}
+}

internal/globals/globals.go

@@ -1,19 +1,24 @@
 // Package globals holds application-wide metadata (name, version,
-// commit) that is populated at build time via linker flags.
+// commit) that is populated at build time via linker flags, or from the
+// build info Go records in the binary when the linker flags set none.
 package globals
 
 import (
 	"regexp"
+	"runtime/debug"
 	"strings"
 	"time"
+
+	"golang.org/x/mod/module"
 )
 
 // Appname is the application name, populated from main().
 var Appname = "vaultik" //nolint:gochecknoglobals // set via -ldflags at build time
 
 // DevVersion is the version a binary reports when it was built without
-// git metadata: script/version emits it outside a git checkout, and an
+// git metadata: script/version emits it outside a git checkout, and a
-// unstamped `go build` keeps it. goreleaser's snapshot template stamps
+// binary keeps it when neither its linker flags nor its Go build info
+// name a version. goreleaser's snapshot template stamps
 // it followed by "-" and the commit it was built from. It is
 // deliberately not a number.
 const DevVersion = "dev"
@@ -32,6 +37,54 @@ var Commit = Unknown //nolint:gochecknoglobals // set via -ldflags at build time
 // CommitDate is the ISO-8601 date of the commit, populated from main().
 var CommitDate = Unknown //nolint:gochecknoglobals // set via -ldflags at build time
 
+// develVersion is the main module version Go records when it cannot
+// tell which version it built.
+const develVersion = "(devel)"
+
+// FillUnsetFromBuildInfo applies FillUnset to Version, Commit and
+// CommitDate, with the build info of the running binary.
+func FillUnsetFromBuildInfo() {
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		return
+	}
+
+	Version, Commit, CommitDate = FillUnset(
+		info, Version, Commit, CommitDate)
+}
+
+// FillUnset returns version, commit and commitDate. Each one that
+// still holds its default ("dev" or empty for the version, "unknown"
+// for the others) is replaced by the value Go recorded in info. A
+// `go install` of a tag sets no linker flags, but Go records the tag
+// as the main module's version. Go records the commit and its time
+// only when it builds from a git checkout. The time is cut to a date,
+// as the Makefile stamps it.
+func FillUnset(
+	info *debug.BuildInfo, version, commit, commitDate string,
+) (string, string, string) {
+	if (version == "" || version == DevVersion) &&
+		info.Main.Version != "" && info.Main.Version != develVersion {
+		version = info.Main.Version
+	}
+
+	for _, s := range info.Settings {
+		switch s.Key {
+		case "vcs.revision":
+			if commit == Unknown {
+				commit = s.Value
+			}
+		case "vcs.time":
+			t, err := time.Parse(time.RFC3339, s.Value)
+			if commitDate == Unknown && err == nil {
+				commitDate = t.UTC().Format(time.DateOnly)
+			}
+		}
+	}
+
+	return version, commit, commitDate
+}
+
 // Author identifies the upstream author of vaultik.
 const Author = "Jeffrey Paul <sneak@sneak.berlin>"
 
@@ -68,8 +121,10 @@ func New() (*Globals, error) {
 // a release. "dev" and goreleaser's snapshot "dev-<sha>" count, and so
 // does what `git describe --tags --always --dirty` gives a make or
 // docker build of an untagged commit: the bare short commit, or
-// tag-N-gHASH on a commit after a tag. Any version ending in "-dirty"
+// tag-N-gHASH on a commit after a tag. A Go pseudo-version counts: Go
-// counts, a modified checkout of a tag ("v1.0.0-dirty") included.
+// records one for a build of an untagged commit without linker flags.
+// Any version ending in "-dirty" or "+dirty" counts, a modified
+// checkout of a tag ("v1.0.0-dirty", "v1.0.0+dirty") included.
 // A plain tag such as "v1.0.0" or "1.0.0" is a release.
 //
 // The empty string counts too. Nothing that knows its version reports
@@ -82,7 +137,8 @@ func New() (*Globals, error) {
 func IsDevVersion(v string) bool {
 	if v == "" || v == Unknown || v == DevVersion ||
 		strings.HasPrefix(v, DevVersion+"-") ||
-		strings.HasSuffix(v, "-dirty") {
+		strings.HasSuffix(v, "-dirty") || strings.HasSuffix(v, "+dirty") ||
+		module.IsPseudoVersion(v) {
 		return true
 	}
 

internal/globals/globals_test.go

@@ -1,6 +1,7 @@
 package globals_test
 
 import (
+	"runtime/debug"
 	"testing"
 
 	"sneak.berlin/go/vaultik/internal/globals"
@@ -59,12 +60,20 @@ func TestIsDevVersion(t *testing.T) {
 		{"1.0.0-rc.1-12-g877eb2f", true},
 		// A tagged commit with uncommitted changes is not that tag.
 		{"v1.0.0-dirty", true},
+		// What Go records for a build without linker flags: a
+		// pseudo-version for an untagged commit, "+dirty" for a
+		// modified checkout.
+		{"v1.0.0-rc3.0.20261111001226-abcdefabcdef", true},
+		{"v0.0.0-20261111001226-abcdefabcdef", true},
+		{"v1.0.1-0.20261111001226-abcdefabcdef", true},
+		{"v1.0.0+dirty", true},
 		// What a tagged build produces (goreleaser's .Version strips
 		// the leading "v"; script/version keeps it).
 		{"1.0.0", false},
 		{"0.1.0", false},
 		{"1.0.0-rc.1", false},
 		{"v1.0.0", false},
+		{"v1.0.0-rc3", false},
 		// A release must not be mistaken for a dev build just because
 		// the string happens to contain "dev".
 		{"1.0.0-dev", false},
@@ -86,10 +95,9 @@ func TestIsDevVersion(t *testing.T) {
 	}
 }
 
-// TestDefaultVersionIsDev pins the linker-flag contract: an unstamped
+// TestDefaultVersionIsDev pins the default: a binary whose linker flags
-// binary (no -ldflags at all, which is what `go build ./...` and `go
+// and build info name no version must report itself as a development
-// install` produce) must report itself as a development build rather
+// build rather than as some default release number.
-// than as some default release number.
 func TestDefaultVersionIsDev(t *testing.T) {
 	t.Parallel()
 
@@ -98,3 +106,104 @@ func TestDefaultVersionIsDev(t *testing.T) {
 			globals.DevVersion)
 	}
 }
+
+// buildInfo returns build info with the given main module version and,
+// when revision is not empty, the commit settings Go records for a
+// build from a git checkout.
+func buildInfo(version, revision string) *debug.BuildInfo {
+	info := &debug.BuildInfo{
+		Main: debug.Module{Path: "sneak.berlin/go/vaultik", Version: version},
+	}
+
+	if revision != "" {
+		info.Settings = []debug.BuildSetting{
+			{Key: "vcs.revision", Value: revision},
+			{Key: "vcs.time", Value: "2026-11-10T23:12:26Z"},
+		}
+	}
+
+	return info
+}
+
+// TestFillUnset covers a binary from `go install` of a tag, which
+// carries no linker flags: it must report the tag. Values the linker
+// flags set are kept.
+func TestFillUnset(t *testing.T) {
+	t.Parallel()
+
+	const (
+		tag = "v1.0.0-rc3"
+		rev = "0123456789abcdef0123456789abcdef01234567"
+	)
+
+	cases := []struct {
+		name                    string
+		info                    *debug.BuildInfo
+		version, commit, date   string
+		wantVersion, wantCommit string
+		wantDate                string
+	}{
+		{
+			name:        "go install of a tag",
+			info:        buildInfo(tag, ""),
+			version:     globals.DevVersion,
+			commit:      globals.Unknown,
+			date:        globals.Unknown,
+			wantVersion: tag,
+			wantCommit:  globals.Unknown,
+			wantDate:    globals.Unknown,
+		},
+		{
+			name:        "empty version",
+			info:        buildInfo(tag, ""),
+			version:     "",
+			commit:      globals.Unknown,
+			date:        globals.Unknown,
+			wantVersion: tag,
+			wantCommit:  globals.Unknown,
+			wantDate:    globals.Unknown,
+		},
+		{
+			name:        "go build in a git checkout",
+			info:        buildInfo(tag, rev),
+			version:     globals.DevVersion,
+			commit:      globals.Unknown,
+			date:        globals.Unknown,
+			wantVersion: tag,
+			wantCommit:  rev,
+			wantDate:    "2026-11-10",
+		},
+		{
+			name:        "Go could not tell the version",
+			info:        buildInfo("(devel)", ""),
+			version:     globals.DevVersion,
+			commit:      globals.Unknown,
+			date:        globals.Unknown,
+			wantVersion: globals.DevVersion,
+			wantCommit:  globals.Unknown,
+			wantDate:    globals.Unknown,
+		},
+		{
+			name:        "linker flags set",
+			info:        buildInfo(tag, rev),
+			version:     "v1.0.0-rc2-4-gabcdef1",
+			commit:      "abcdef1",
+			date:        "2026-11-01",
+			wantVersion: "v1.0.0-rc2-4-gabcdef1",
+			wantCommit:  "abcdef1",
+			wantDate:    "2026-11-01",
+		},
+	}
+
+	for _, tc := range cases {
+		version, commit, date := globals.FillUnset(
+			tc.info, tc.version, tc.commit, tc.date)
+
+		if version != tc.wantVersion || commit != tc.wantCommit ||
+			date != tc.wantDate {
+			t.Errorf("%s: got %q, %q, %q; want %q, %q, %q", tc.name,
+				version, commit, date,
+				tc.wantVersion, tc.wantCommit, tc.wantDate)
+		}
+	}
+}

internal/pidlock/pidlock.go

@@ -11,6 +11,7 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/adrg/xdg"
 	"golang.org/x/sys/unix"
 )
 
@@ -29,8 +30,20 @@ const (
 	lockDirPerm = 0o700
 	// pidFilePerm is the mode for the PID file (owner-only).
 	pidFilePerm = 0o600
+	// pidFileName is the name of the PID file in the lock directory.
+	pidFileName = "vaultik.pid"
 )
 
+// Dir returns the directory that holds vaultik's PID file.
+func Dir() string {
+	return filepath.Join(xdg.DataHome, "vaultik")
+}
+
+// Path returns the path of the PID file that Acquire uses in lockDir.
+func Path(lockDir string) string {
+	return filepath.Join(lockDir, pidFileName)
+}
+
 // Acquire attempts to acquire a PID lock in the specified directory.
 // If another process holds the lock, it returns ErrAlreadyRunning with
 // that process's PID. On success, it writes the current PID to the lock
@@ -42,7 +55,7 @@ func Acquire(lockDir string) (*Lock, error) {
 		return nil, fmt.Errorf("creating lock directory: %w", err)
 	}
 
-	lockPath := filepath.Join(lockDir, "vaultik.pid")
+	lockPath := Path(lockDir)
 
 	// No O_TRUNC: the file may hold the PID of the process that has the
 	// lock, which the error below reports.

internal/snapshot/index_and_lock_files_test.go

@@ -0,0 +1,65 @@
+package snapshot_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/vaultik/internal/database"
+	"sneak.berlin/go/vaultik/internal/snapshot"
+)
+
+// A backup of the directory that holds vaultik's index and PID file
+// stores neither, with no exclude pattern set, and still stores the
+// files beside them. See https://git.eeqj.de/sneak/vaultik/issues/421.
+func TestScanSkipsIndexAndLockFiles(t *testing.T) {
+	t.Parallel()
+
+	const dataDir = "/home/user/.local/share/vaultik"
+
+	indexAndLockFiles := append(database.IndexFiles(dataDir+"/index.sqlite"),
+		dataDir+"/vaultik.pid")
+
+	fs := afero.NewMemMapFs()
+	for _, p := range append(indexAndLockFiles, dataDir+"/notes.txt") {
+		require.NoError(t, afero.WriteFile(fs, p, []byte("data"), 0o600))
+	}
+
+	db, err := database.NewTestDB()
+	require.NoError(t, err)
+
+	defer func() { _ = db.Close() }()
+
+	repos := database.NewRepositories(db)
+
+	scanner := snapshot.NewScanner(snapshot.ScannerConfig{
+		FS:               fs,
+		ChunkSize:        64 * 1024,
+		Repositories:     repos,
+		MaxBlobSize:      1024 * 1024,
+		CompressionLevel: 3,
+		AgeRecipients: []string{
+			"age1ql3z7hjy54pw3hyww5ayyfg7zqgvc7w3j2elw8zmrj2kg5sfn9aqmcac8p"},
+		IndexAndLockFiles: indexAndLockFiles,
+	})
+	require.NotNil(t, scanner)
+
+	ctx := context.Background()
+	createSnapshotRecord(ctx, t, repos, "test-snapshot")
+
+	result, err := scanner.Scan(ctx, "/home/user", "test-snapshot")
+	require.NoError(t, err)
+
+	require.Equal(t, 1, result.FilesScanned)
+
+	stored, err := repos.Files.GetByPath(ctx, dataDir+"/notes.txt")
+	require.NoError(t, err)
+	require.NotNil(t, stored, "a file beside the index is stored")
+
+	for _, p := range indexAndLockFiles {
+		f, err := repos.Files.GetByPath(ctx, p)
+		require.NoError(t, err)
+		require.Nil(t, f, "%s is not stored", p)
+	}
+}

internal/snapshot/module.go

@@ -2,11 +2,13 @@ package snapshot
 
 import (
 	"os"
+	"path/filepath"
 
 	"github.com/spf13/afero"
 	"go.uber.org/fx"
 	"sneak.berlin/go/vaultik/internal/config"
 	"sneak.berlin/go/vaultik/internal/database"
+	"sneak.berlin/go/vaultik/internal/pidlock"
 	"sneak.berlin/go/vaultik/internal/storage"
 	"sneak.berlin/go/vaultik/internal/ui"
 )
@@ -62,9 +64,52 @@ func provideScannerFactory(
 			EnableProgress:     params.EnableProgress,
 			UI:                 params.UI,
 			Exclude:            excludes,
+			IndexAndLockFiles:  indexAndLockFiles(cfg.IndexPath, pidlock.Dir()),
 			SkipErrors:         params.SkipErrors,
 			PreviousSnapshotID: params.PreviousSnapshotID,
 			DeviceNumber:       params.DeviceNumber,
 		})
 	}
 }
+
+// indexAndLockFiles returns the paths of the index at indexPath, its side
+// files and the PID file in lockDir. Symlinks in their directories are
+// resolved, as they are in the snapshot's source paths, so the scan finds
+// them under the same names. If indexPath is a symlink, the file it points
+// to and that file's side files are returned too.
+func indexAndLockFiles(indexPath, lockDir string) []string {
+	paths := append(database.IndexFiles(indexPath), pidlock.Path(lockDir))
+	for i, p := range paths {
+		paths[i] = resolveParentDir(p)
+	}
+
+	// SQLite writes the file a symlinked index points to and keeps the
+	// side files beside that file. The database package creates the index
+	// before the scanner is built, so the link resolves.
+	index := resolveParentDir(indexPath)
+
+	target, err := filepath.EvalSymlinks(index)
+	if err == nil && target != index {
+		paths = append(paths, database.IndexFiles(target)...)
+	}
+
+	return paths
+}
+
+// resolveParentDir returns the absolute form of path with the symlinks in
+// its parent directory resolved. If the parent directory cannot be
+// resolved, it returns the absolute form unresolved. If path has no
+// absolute form, it returns path.
+func resolveParentDir(path string) string {
+	abs, err := filepath.Abs(path)
+	if err != nil {
+		return path
+	}
+
+	dir, err := filepath.EvalSymlinks(filepath.Dir(abs))
+	if err != nil {
+		return abs
+	}
+
+	return filepath.Join(dir, filepath.Base(abs))
+}

internal/snapshot/module_test.go

@@ -0,0 +1,32 @@
+//nolint:testpackage // exercises the unexported indexAndLockFiles helper
+package snapshot
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// The scan walks source paths with symlinks resolved, so vaultik's own
+// files are named the same way, or a symlinked home would back them up.
+func TestIndexAndLockFilesResolvesSymlinkedDirectory(t *testing.T) {
+	t.Parallel()
+
+	realDir, err := filepath.EvalSymlinks(t.TempDir())
+	require.NoError(t, err)
+
+	link := filepath.Join(t.TempDir(), "link")
+	require.NoError(t, os.Symlink(realDir, link))
+
+	paths := indexAndLockFiles(filepath.Join(link, "index.sqlite"), link)
+
+	require.Equal(t, []string{
+		filepath.Join(realDir, "index.sqlite"),
+		filepath.Join(realDir, "index.sqlite-wal"),
+		filepath.Join(realDir, "index.sqlite-shm"),
+		filepath.Join(realDir, "index.sqlite-journal"),
+		filepath.Join(realDir, "vaultik.pid"),
+	}, paths)
+}

internal/snapshot/scanner.go

@@ -20,6 +20,7 @@ import (
 	"sneak.berlin/go/vaultik/internal/blob"
 	"sneak.berlin/go/vaultik/internal/chunker"
 	"sneak.berlin/go/vaultik/internal/database"
+	"sneak.berlin/go/vaultik/internal/exclude"
 	"sneak.berlin/go/vaultik/internal/log"
 	"sneak.berlin/go/vaultik/internal/storage"
 	"sneak.berlin/go/vaultik/internal/types"
@@ -67,6 +68,9 @@ type Scanner struct {
 	currentSourcePath string
 	exclude           []string          // Glob patterns for files/directories to exclude
 	compiledExclude   []compiledPattern // Compiled glob patterns
+	// indexAndLockFiles holds the paths of vaultik's own working files,
+	// which the scan treats as excluded (ScannerConfig.IndexAndLockFiles).
+	indexAndLockFiles map[string]struct{}
 	progress          *ProgressReporter
 	// skipErrors skips files that cannot be opened or read (logged loudly);
 	// packer, database, encryption, and upload errors still abort the run.
@@ -133,6 +137,11 @@ type ScannerConfig struct {
 	EnableProgress   bool       // Enable the live progress reporter (ETAs, throughput)
 	UI               *ui.Writer // Where user-facing scanner messages go; nil = discard
 	Exclude          []string   // Glob patterns for files/directories to exclude
+	// IndexAndLockFiles are the absolute paths of vaultik's own working
+	// files: the index, its side files and the PID file. The scan treats
+	// them as excluded, whatever Exclude says, since a copy taken while
+	// they are being written is torn.
+	IndexAndLockFiles []string
 	// SkipErrors skips files that cannot be opened or read (log loudly but
 	// continue); packer, database, encryption, and upload errors still abort.
 	SkipErrors bool
@@ -213,8 +222,12 @@ func NewScanner(cfg ScannerConfig) *Scanner {
 		progress = NewProgressReporter()
 	}
 
-	// Compile exclude patterns
+	compiledExclude, err := compileExcludePatterns(cfg.Exclude)
-	compiledExclude := compileExcludePatterns(cfg.Exclude)
+	if err != nil {
+		log.Error("Failed to compile exclude patterns", "error", err)
+
+		return nil
+	}
 
 	uiw := cfg.UI
 	if uiw == nil {
@@ -226,6 +239,11 @@ func NewScanner(cfg ScannerConfig) *Scanner {
 		deviceNumber = deviceNumberFromStat
 	}
 
+	indexAndLockFiles := make(map[string]struct{}, len(cfg.IndexAndLockFiles))
+	for _, p := range cfg.IndexAndLockFiles {
+		indexAndLockFiles[filepath.Clean(p)] = struct{}{}
+	}
+
 	return &Scanner{
 		fs:                 cfg.FS,
 		chunker:            chunker.NewChunker(cfg.ChunkSize),
@@ -237,6 +255,7 @@ func NewScanner(cfg ScannerConfig) *Scanner {
 		ageRecipient:       strings.Join(cfg.AgeRecipients, ","),
 		exclude:            cfg.Exclude,
 		compiledExclude:    compiledExclude,
+		indexAndLockFiles:  indexAndLockFiles,
 		progress:           progress,
 		skipErrors:         cfg.SkipErrors,
 		previousSnapshotID: cfg.PreviousSnapshotID,
@@ -1861,7 +1880,13 @@ func (s *Scanner) uploadBlobIfNeeded(
 	err = s.storage.PutWithProgress(ctx, blobPath, blobWithReader.Reader,
 		finishedBlob.Compressed, progressCallback)
 	if err != nil {
-		log.Error("Failed to upload blob", "hash", finishedBlob.Hash, "error", err)
+		// The record is at info level: the returned error ends the backup
+		// and is printed as its ERROR: line. Only an interrupt cancels
+		// ctx, and the user is told about it, so an upload it stopped is
+		// not logged as a storage failure.
+		if ctx.Err() == nil {
+			log.Info("Failed to upload blob", "hash", finishedBlob.Hash, "error", err)
+		}
 
 		return 0, false, fmt.Errorf("uploading blob to storage: %w", err)
 	}
@@ -2248,8 +2273,9 @@ func (s *Scanner) detectDeletedFiles(
 
 // excludedOrInExcludedDir reports whether filePath, which is at or
 // beneath rootPath, or any directory between rootPath and it, matches an
-// exclude pattern. A pattern such as */.local/share/Trash matches the
+// exclude pattern or is one of vaultik's own files. A pattern such as
-// directory but not the files inside it, which the walk skips too.
+// */.local/share/Trash matches the directory but not the files inside it,
+// which the walk skips too.
 func (s *Scanner) excludedOrInExcludedDir(filePath, rootPath string) bool {
 	for p := filePath; len(p) > len(rootPath); p = filepath.Dir(p) {
 		if s.shouldExclude(p, rootPath) {
@@ -2297,51 +2323,18 @@ func wrapPermissionError(path string, err error) error {
 		"with --skip-errors to continue past unreadable files)", path, err)
 }
 
-// compileExcludePatterns compiles the exclude patterns into glob matchers
+// compileExcludePatterns compiles the exclude patterns into glob matchers.
-func compileExcludePatterns(patterns []string) []compiledPattern {
+// Config.Validate has already refused a pattern that does not compile.
+func compileExcludePatterns(patterns []string) ([]compiledPattern, error) {
 	var compiled []compiledPattern
 
 	for _, p := range patterns {
-		if p == "" {
+		globs, anchored, err := exclude.Compile(p)
-			continue
-		}
-
-		// Check if pattern is anchored (starts with /)
-		anchored := strings.HasPrefix(p, "/")
-
-		pattern := p
-		if anchored {
-			pattern = p[1:] // Remove leading /
-		}
-
-		// Remove trailing slash if present (directory indicator)
-		pattern = strings.TrimSuffix(pattern, "/")
-
-		// A leading "**/" demands a "/" before the name and so misses an
-		// entry directly under the source path. It means "at every depth",
-		// which is what an unanchored pattern already does, so drop the
-		// prefix and match unanchored: as in gitignore, "**/x" and
-		// "/**/x" then also match a top-level "x".
-		if rest, found := strings.CutPrefix(pattern, "**/"); found {
-			pattern = rest
-			anchored = false
-		}
-
-		// Likewise "/**/" inside a pattern demands two slashes, so
-		// "a/**/*.log" misses "a/x.log". As in gitignore it stands for
-		// zero or more directories, so also compile the pattern with it
-		// made a single "/". The glob library's {a,b} is no help: with a
-		// "**" inside it in mid-pattern, it misses paths it should match.
-		for _, variant := range doubleStarVariants(pattern) {
-			// For patterns without path separators, we need to match them as components
-			// e.g., ".git" should match ".git" anywhere in the path
-			g, err := glob.Compile(variant, '/')
 		if err != nil {
-				log.Warn("Invalid exclude pattern, skipping", "pattern", p, "error", err)
+			return nil, err
-
-				break
 		}
 
+		for _, g := range globs {
 			compiled = append(compiled, compiledPattern{
 				pattern:  g,
 				anchored: anchored,
@@ -2350,32 +2343,18 @@ func compileExcludePatterns(patterns []string) []compiledPattern {
 		}
 	}
 
-	return compiled
+	return compiled, nil
-}
-
-// doubleStarVariants returns pattern once for every way of keeping each
-// "/**/" in it or making it a single "/".
-func doubleStarVariants(pattern string) []string {
-	const doubleStar = "/**/"
-
-	before, after, found := strings.Cut(pattern, doubleStar)
-	if !found {
-		return []string{pattern}
-	}
-
-	var variants []string
-
-	for _, rest := range doubleStarVariants(after) {
-		variants = append(variants, before+doubleStar+rest, before+"/"+rest)
-	}
-
-	return variants
 }
 
 // shouldExclude checks if a path should be excluded based on exclude patterns
+// or because it is one of vaultik's own working files.
 // filePath is the full path to the file
 // rootPath is the root of the backup source directory
 func (s *Scanner) shouldExclude(filePath, rootPath string) bool {
+	if _, ok := s.indexAndLockFiles[filePath]; ok {
+		return true
+	}
+
 	if len(s.compiledExclude) == 0 {
 		return false
 	}

internal/snapshot/upload_cancel_log_test.go

@@ -0,0 +1,135 @@
+//nolint:testpackage // exercises the unexported uploadBlobIfNeeded
+package snapshot
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"sneak.berlin/go/vaultik/internal/blob"
+	"sneak.berlin/go/vaultik/internal/log"
+	"sneak.berlin/go/vaultik/internal/storage"
+	"sneak.berlin/go/vaultik/internal/storage/faultstore"
+	"sneak.berlin/go/vaultik/internal/ui"
+)
+
+const uploadFailedLogMessage = "Failed to upload blob"
+
+// uploadTestBlob uploads a small blob through store.
+func uploadTestBlob(ctx context.Context, store storage.Storer) error {
+	data := []byte("blob data")
+	s := &Scanner{storage: store, ui: ui.NewWithColor(io.Discard, false)}
+
+	_, _, err := s.uploadBlobIfNeeded(ctx, "blobs/test", &blob.WithReader{
+		FinishedBlob: &blob.FinishedBlob{
+			Hash:       "test",
+			Compressed: int64(len(data)),
+		},
+		Reader: bytes.NewReader(data),
+	}, time.Now(), &ScanResult{})
+
+	return err
+}
+
+// captureLog runs fn and returns what the logger wrote to stderr
+// meanwhile, at the --verbose level. The logger writes to the os.Stderr
+// it finds when it is initialized, so os.Stderr is pointed at a file
+// first. Not parallel-safe: os.Stderr and the logger are process-global.
+func captureLog(t *testing.T, fn func()) string {
+	t.Helper()
+
+	stderrPath := filepath.Join(t.TempDir(), "stderr")
+
+	stderrFile, err := os.Create(stderrPath) //nolint:gosec // G304: test temp path
+	if err != nil {
+		t.Fatalf("creating stderr file: %v", err)
+	}
+
+	previous := os.Stderr
+	os.Stderr = stderrFile
+
+	log.Initialize(log.Config{Verbose: true})
+
+	fn()
+
+	os.Stderr = previous
+
+	log.Initialize(log.Config{})
+
+	_ = stderrFile.Close()
+
+	captured, err := os.ReadFile(stderrPath) //nolint:gosec // G304: test temp path
+	if err != nil {
+		t.Fatalf("reading stderr file: %v", err)
+	}
+
+	return string(captured)
+}
+
+// An upload stopped by Ctrl-C or SIGTERM is not logged as an error; the
+// interrupted message is all the user sees. See
+// https://git.eeqj.de/sneak/vaultik/issues/434.
+//
+//nolint:paralleltest // captureLog replaces os.Stderr
+func TestInterruptedUploadIsNotLoggedAsError(t *testing.T) {
+	inner, err := storage.NewFileStorer(t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	t.Cleanup(cancel)
+
+	// The user interrupts mid-upload. The injected error does not wrap
+	// context.Canceled, so only ctx shows why the upload failed.
+	store := faultstore.New(inner)
+	store.OnPut = func(string) faultstore.PutAction {
+		cancel()
+
+		return faultstore.PutFail
+	}
+
+	var uploadErr error
+
+	stderr := captureLog(t, func() { uploadErr = uploadTestBlob(ctx, store) })
+
+	if uploadErr == nil {
+		t.Fatal("expected the upload to fail")
+	}
+
+	if strings.Contains(stderr, uploadFailedLogMessage) {
+		t.Errorf("interrupted upload logged as a failure: %q", stderr)
+	}
+}
+
+// An upload that fails for any other reason is still logged.
+//
+//nolint:paralleltest // captureLog replaces os.Stderr
+func TestFailedUploadIsLogged(t *testing.T) {
+	inner, err := storage.NewFileStorer(t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	store := faultstore.New(inner)
+	store.OnPut = func(string) faultstore.PutAction { return faultstore.PutFail }
+
+	var uploadErr error
+
+	stderr := captureLog(t, func() {
+		uploadErr = uploadTestBlob(context.Background(), store)
+	})
+
+	if uploadErr == nil {
+		t.Fatal("expected the upload to fail")
+	}
+
+	if !strings.Contains(stderr, uploadFailedLogMessage) {
+		t.Errorf("failed upload not logged: %q", stderr)
+	}
+}

internal/vaultik/blob_fetch.go

@@ -22,6 +22,10 @@ var errBlobHashMismatch = errors.New("blob hash mismatch")
 var errBlobNotFullyRead = errors.New(
 	"blob closed before fully read; hash not verified")
 
+// errWrongPrivateKeyForBlob is returned when the configured key parses
+// but is not one of the keys a blob was encrypted to.
+var errWrongPrivateKeyForBlob = errors.New("cannot decrypt this blob")
+
 // hashVerifyReader wraps a blobgen.Reader and verifies the double-SHA-256 hash
 // of decrypted plaintext when Close is called. It reuses the hash that
 // blobgen.Reader already computes internally via its TeeReader, avoiding
@@ -87,10 +91,14 @@ func (v *Vaultik) FetchAndDecryptBlob(
 		return nil, err
 	}
 
-	reader, err := blobgen.NewReader(rc, identities...)
+	reader, err := v.newBlobReader(rc, identities)
 	if err != nil {
 		_ = rc.Close()
 
+		if errors.Is(err, errWrongPrivateKeyForBlob) {
+			return nil, err
+		}
+
 		return nil, fmt.Errorf("creating blob reader: %w", err)
 	}
 
@@ -102,6 +110,28 @@ func (v *Vaultik) FetchAndDecryptBlob(
 	}, nil
 }
 
+// newBlobReader opens the decrypting reader for a blob. When none of the
+// identities can decrypt it, the error says in plain words that the
+// configured private key is not one of the keys the blob was encrypted
+// to and names where the key was configured.
+func (v *Vaultik) newBlobReader(
+	r io.Reader, identities []age.Identity,
+) (*blobgen.Reader, error) {
+	blobReader, err := blobgen.NewReader(r, identities...)
+
+	if _, ok := errors.AsType[*age.NoIdentityMatchError](err); ok {
+		return nil, fmt.Errorf(
+			"%w: the private key in %s is not one of the keys the blob was encrypted to",
+			errWrongPrivateKeyForBlob, v.Config.AgeSecretKeySourceName())
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	return blobReader, nil
+}
+
 // FetchBlob downloads a blob and returns a reader for the encrypted data.
 // The reader is closed as soon as ctx is cancelled, which ends a read
 // blocked inside it. A storage error is returned as is: restore and deep

internal/vaultik/destination_marker.go

@@ -51,7 +51,7 @@ func (v *Vaultik) checkDestinationMarker() error {
 	}
 
 	// Config is nil only in tests, which then record no binding (see
-	// EnsureStorageBinding).
+	// checkStorageBinding).
 	if v.Config != nil {
 		stored, configured, err := v.storageBinding()
 		if err != nil {
@@ -83,11 +83,19 @@ func (v *Vaultik) checkDestinationMarker() error {
 	return nil
 }
 
-// markDestination checks the backup destination store with
+// markDestination refuses a local index bound to a different
-// checkDestinationMarker and then writes the marker, so a first backup
+// destination, checks the backup destination store for its marker,
-// marks its destination and a later one writes the same text again.
+// writes the marker, and then records the binding. A first backup marks
+// its destination and a later one writes the same text again. The
+// binding is recorded last, so a first backup that cannot write to the
+// destination leaves the local index unbound.
 func (v *Vaultik) markDestination() error {
-	err := v.checkDestinationMarker()
+	err := v.checkStorageBinding()
+	if err != nil {
+		return err
+	}
+
+	err = v.checkDestinationMarker()
 	if err != nil {
 		return err
 	}
@@ -99,5 +107,5 @@ func (v *Vaultik) markDestination() error {
 			destinationMarkerKey, err)
 	}
 
-	return nil
+	return v.EnsureStorageBinding()
 }

internal/vaultik/missing_destination_test.go

@@ -7,6 +7,7 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 	"testing"
 
 	"github.com/spf13/afero"
@@ -24,19 +25,28 @@ import (
 // that is not plugged in, cannot be listed. It is not an empty store, so
 // no command may conclude from it that the local snapshots are gone.
 
-// newFileDestinationVaultik returns a Vaultik that backs up the
+// newFileDestinationVaultik writes the fault source tree and returns a
-// snapshot named "first" to a file:// destination at storeDir.
+// Vaultik that backs it up to a file:// destination at storeDir.
 func newFileDestinationVaultik(
 	ctx context.Context, t *testing.T, storeDir string,
 ) (*vaultik.Vaultik, *database.Repositories) {
 	t.Helper()
 
-	osFs := afero.NewOsFs()
 	tempDir := t.TempDir()
 	dataDir := filepath.Join(tempDir, "src")
-	dbPath := filepath.Join(tempDir, "index.sqlite")
+	writeFaultSourceTree(t, afero.NewOsFs(), dataDir)
 
-	writeFaultSourceTree(t, osFs, dataDir)
+	return openFileDestinationVaultik(ctx, t, storeDir, dataDir,
+		filepath.Join(tempDir, "index.sqlite"))
+}
+
+// openFileDestinationVaultik returns a Vaultik that backs up dataDir to a
+// file:// destination at storeDir, with its local index at dbPath. The
+// index is closed when the test ends.
+func openFileDestinationVaultik(
+	ctx context.Context, t *testing.T, storeDir, dataDir, dbPath string,
+) (*vaultik.Vaultik, *database.Repositories) {
+	t.Helper()
 
 	store, err := storage.NewFileStorer(storeDir)
 	require.NoError(t, err)
@@ -48,22 +58,84 @@ func newFileDestinationVaultik(
 	repos := database.NewRepositories(db)
 	cfg := changedFileConfig(dataDir, dbPath)
 
-	return newBackupVaultik(ctx, cfg, store, repos, db, osFs), repos
+	return newBackupVaultik(ctx, cfg, store, repos, db, afero.NewOsFs()), repos
+}
+
+// firstBackup is one backup of the snapshot named "first" to a file://
+// destination. dir holds its source tree in src, its store in store and
+// its closed local index in index/index.sqlite. The first test that
+// needs it makes it, and TestMain removes it. Every test that copies it
+// backs up the same source tree, so no test may change that tree.
+//
+//nolint:gochecknoglobals // made once and shared by the tests that copy it
+var firstBackup struct {
+	once  sync.Once
+	dir   string
+	ready bool
+}
+
+// TestMain removes firstBackup once every test has run.
+func TestMain(m *testing.M) {
+	code := m.Run()
+
+	_ = os.RemoveAll(firstBackup.dir)
+
+	os.Exit(code)
+}
+
+// makeFirstBackup writes the fault source tree and backs it up as the
+// snapshot named "first", all in a new directory that it records in
+// firstBackup.
+func makeFirstBackup(ctx context.Context, t *testing.T) {
+	t.Helper()
+
+	dir, err := os.MkdirTemp("", "vaultik-first-backup-")
+	require.NoError(t, err)
+
+	firstBackup.dir = dir
+	storeDir := filepath.Join(dir, "store")
+	dataDir := filepath.Join(dir, "src")
+	indexDir := filepath.Join(dir, "index")
+
+	require.NoError(t, os.Mkdir(storeDir, 0o750))
+	require.NoError(t, os.Mkdir(indexDir, 0o750))
+	writeFaultSourceTree(t, afero.NewOsFs(), dataDir)
+
+	v, _ := openFileDestinationVaultik(ctx, t, storeDir, dataDir,
+		filepath.Join(indexDir, "index.sqlite"))
+	require.NoError(t, backUp(v, "first"))
+	require.NoError(t, v.DB.Close())
+
+	firstBackup.ready = true
 }
 
 // backUpToFileDestination creates the directory storeDir, as a user must
-// before the first backup, and backs up the snapshot named "first" to a
+// before the first backup, and returns a Vaultik whose file://
-// file:// destination there. Everything the returned Vaultik prints
+// destination there holds a backup of the snapshot named "first". The
-// after the backup goes to the returned buffer.
+// store and the local index are copies of firstBackup's, which is faster
+// than backing up in every test. The returned Vaultik backs up a source
+// tree shared with every other caller, so no test may change that tree.
+// Everything the returned Vaultik prints after the backup goes to the
+// returned buffer.
 func backUpToFileDestination(
 	ctx context.Context, t *testing.T, storeDir string,
 ) (*vaultik.Vaultik, *database.Repositories, *bytes.Buffer) {
 	t.Helper()
 
-	require.NoError(t, os.MkdirAll(storeDir, 0o750))
+	firstBackup.once.Do(func() { makeFirstBackup(ctx, t) })
+	require.True(t, firstBackup.ready, "another test failed to make firstBackup")
 
-	v, repos := newFileDestinationVaultik(ctx, t, storeDir)
+	require.NoError(t, os.MkdirAll(storeDir, 0o750))
-	require.NoError(t, backUp(v, "first"))
+	require.NoError(t, os.CopyFS(storeDir,
+		os.DirFS(filepath.Join(firstBackup.dir, "store"))))
+
+	indexDir := t.TempDir()
+	require.NoError(t, os.CopyFS(indexDir,
+		os.DirFS(filepath.Join(firstBackup.dir, "index"))))
+
+	v, repos := openFileDestinationVaultik(ctx, t, storeDir,
+		filepath.Join(firstBackup.dir, "src"),
+		filepath.Join(indexDir, "index.sqlite"))
 
 	out := &bytes.Buffer{}
 	v.Stdout = out

internal/vaultik/prune.go

@@ -68,7 +68,7 @@ func (v *Vaultik) NukeRemote(force bool) error {
 	// the same way, so the advice below must not follow these errors.
 	// The listing also fails on a destination that answers that it has
 	// no marker while the local index holds snapshots.
-	err := v.EnsureStorageBinding()
+	err := v.checkStorageBinding()
 	if err != nil {
 		return err
 	}
@@ -192,7 +192,7 @@ type PruneBlobsResult struct {
 // PruneDatabase or PruneBlobs individually unless it specifically wants
 // one half.
 func (v *Vaultik) Prune(opts *PruneOptions) error {
-	err := v.EnsureStorageBinding()
+	err := v.checkStorageBinding()
 	if err != nil {
 		return err
 	}
@@ -267,7 +267,7 @@ func (v *Vaultik) PruneBlobs(opts *PruneOptions) error {
 
 	if !v.confirmPrune(opts, len(unreferencedBlobs), totalSize,
 		dirsWithoutManifest) {
-		return nil
+		return ErrNotConfirmed
 	}
 
 	v.deleteUnreferencedBlobs(unreferencedBlobs, allBlobs, result)

internal/vaultik/prune_metadata_dir_test.go

@@ -176,7 +176,8 @@ func TestPruneDeclinedKeepsMetadataDirWithoutManifest(t *testing.T) {
 
 	env.v.Stdin = strings.NewReader("n\n")
 
-	require.NoError(t, env.v.PruneBlobs(&vaultik.PruneOptions{}))
+	require.ErrorIs(t, env.v.PruneBlobs(&vaultik.PruneOptions{}),
+		vaultik.ErrNotConfirmed)
 
 	assert.True(t, env.store.hasKey(leftDB),
 		"a declined prune must keep the directory")

internal/vaultik/remove_quiet_test.go

@@ -54,9 +54,10 @@ func TestPurgeSnapshots_QuietPromptListsSnapshots(t *testing.T) {
 	v.UI.SetQuiet(true)
 
 	// Stdin is empty, so the prompt reads no answer and cancels.
-	require.NoError(t, v.PurgeSnapshotsWithOptions(&vaultik.SnapshotPurgeOptions{
+	err := v.PurgeSnapshotsWithOptions(&vaultik.SnapshotPurgeOptions{
 		KeepLatest: true,
-	}))
+	})
+	require.ErrorIs(t, err, vaultik.ErrNotConfirmed)
 
 	assert.Contains(t, out.String(), snapHomeT0)
 	assert.Contains(t, out.String(), "Delete 1 snapshot(s)? [y/N]")
@@ -77,7 +78,8 @@ func TestPruneBlobs_QuietPromptShowsBlobTotal(t *testing.T) {
 	addBlob(t, env.store.testStorer, testBlobHashA)
 
 	// Stdin is empty, so the prompt reads no answer and cancels.
-	require.NoError(t, env.v.PruneBlobs(&vaultik.PruneOptions{}))
+	require.ErrorIs(t, env.v.PruneBlobs(&vaultik.PruneOptions{}),
+		vaultik.ErrNotConfirmed)
 
 	assert.Contains(t, env.stdout.String(),
 		"Found 1 unreferenced blob(s) totaling")

internal/vaultik/remove_snapshot_test.go

@@ -337,6 +337,27 @@ func TestRemoveSnapshot_DefaultRemovesMetadataNotBlobs(t *testing.T) {
 	assert.Contains(t, out, "vaultik prune")
 }
 
+// TestRemoveSnapshot_DeclinedIsError checks that answering no to the
+// prompt keeps the snapshot and returns ErrNotConfirmed, so the command
+// exits non-zero.
+func TestRemoveSnapshot_DeclinedIsError(t *testing.T) {
+	log.Initialize(log.Config{})
+	t.Parallel()
+
+	store := newTestStorer()
+	addManifest(t, store, "snapshot-001", nil)
+
+	tv := vaultik.NewForTesting(store)
+	tv.Repositories = newLocalIndex(t, "snapshot-001")
+	tv.Stdin.WriteString("n\n")
+
+	_, err := tv.RemoveSnapshot("snapshot-001", &vaultik.RemoveOptions{})
+
+	require.ErrorIs(t, err, vaultik.ErrNotConfirmed)
+	assert.True(t, store.hasKey(remoteKeyPath("snapshot-001")))
+	assert.Contains(t, tv.Stdout.String(), "Cancelled")
+}
+
 func TestRemoveSnapshot_DryRun(t *testing.T) {
 	log.Initialize(log.Config{})
 	t.Parallel()

internal/vaultik/restore.go

@@ -40,6 +40,9 @@ var (
 	// which is secret, so the message is safe to print and log.
 	errInvalidAgeSecretKey = errors.New(
 		"configured age secret key holds no usable age identity")
+	// errWrongPrivateKey is returned when the configured key parses but
+	// is not one of the keys the snapshot was encrypted to.
+	errWrongPrivateKey          = errors.New("cannot decrypt this snapshot")
 	errBlobMissingFromIndex     = errors.New("blob hash missing from blob index")
 	errChunkNotInAnyBlob        = errors.New("chunk not found in any blob")
 	errBlobIDNotInHashIndex     = errors.New("blob id missing from hash index")
@@ -106,7 +109,12 @@ type RestoreResult struct {
 	BytesDownloaded int64
 	Duration        time.Duration
 	FilesFailed     int
-	FailedFiles     []string // Paths of files that failed to restore
+	FailedFiles     []string // Paths of files that failed to restore for their own reason
+	// Blobs that could not be downloaded, and the paths of the files
+	// skipped because they need one of them. Those files are counted in
+	// FilesFailed but not listed in the summary.
+	BlobsFailed            int
+	FilesNeedingFailedBlob []string
 	// Verification results (only populated if Verify option is set)
 	FilesVerified     int
 	BytesVerified     int64
@@ -128,10 +136,19 @@ func (v *Vaultik) Restore(opts *RestoreOptions) error {
 		"paths", opts.Paths,
 	)
 
+	remoteKey, err := v.resolveSnapshotRemoteKey(opts.SnapshotID)
+	if err != nil {
+		return err
+	}
+
 	// Step 1: Download and decrypt the snapshot metadata database
 	log.Info("Downloading snapshot metadata...")
 
-	tempDB, tempDir, err := v.downloadSnapshotDB(opts.SnapshotID, identities)
+	tempDB, tempDir, err := v.downloadSnapshotDB(opts.SnapshotID, remoteKey, identities)
+	if errors.Is(err, errWrongPrivateKey) {
+		return err
+	}
+
 	if err != nil {
 		return fmt.Errorf("downloading snapshot database: %w", err)
 	}
@@ -226,6 +243,11 @@ func (v *Vaultik) finishRestore(
 	if result.FilesFailed > 0 {
 		v.UI.Warningf("%d file(s) failed to restore:", result.FilesFailed)
 
+		if result.BlobsFailed > 0 {
+			v.UI.Detailf("%d of them need a blob that could not be read (%d blob(s) in all).",
+				len(result.FilesNeedingFailedBlob), result.BlobsFailed)
+		}
+
 		for _, path := range result.FailedFiles {
 			v.UI.Detailf("%s", v.UI.Path(path))
 		}
@@ -323,6 +345,28 @@ func (v *Vaultik) restoreIdentities() ([]age.Identity, error) {
 	return identities, nil
 }
 
+// newSnapshotDBReader opens the decrypting reader for a snapshot
+// database. When none of the identities can decrypt it, the error says
+// in plain words that the configured private key is the wrong one and
+// names where it was configured.
+func (v *Vaultik) newSnapshotDBReader(
+	r io.Reader, identities []age.Identity,
+) (*blobgen.Reader, error) {
+	blobReader, err := blobgen.NewReader(r, identities...)
+
+	if _, ok := errors.AsType[*age.NoIdentityMatchError](err); ok {
+		return nil, fmt.Errorf(
+			"%w: the private key in %s is not one of the keys the backup was encrypted to",
+			errWrongPrivateKey, v.Config.AgeSecretKeySourceName())
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	return blobReader, nil
+}
+
 // restoreAllFiles processes files in blob-locality order: drain every
 // file whose blob set is on disk, download the missing blobs for the
 // pending file with the smallest uncached count, repeat. This keeps
@@ -494,8 +538,8 @@ func (v *Vaultik) runRestoreLoop(
 // Returns false when nothing is pending download (the caller stops).
 //
 // A blob that cannot be downloaded is reported through
-// handleRestoreFileError for every pending file that references it, so
+// handleRestoreBlobError, so it aborts the restore unless --skip-errors
-// it aborts the restore unless --skip-errors is set.
+// is set.
 func (s *restoreSession) downloadNextBlobSet(
 	plan *restorePlan, filesByID map[types.FileID]*database.File,
 ) (bool, error) {
@@ -528,12 +572,11 @@ func (s *restoreSession) downloadNextBlobSet(
 				return false, err
 			}
 
-			for _, fileID := range plan.filesReferencingBlob(hash) {
+			blobErr := s.v.handleRestoreBlobError(
-				fileErr := s.v.handleRestoreFileError(
+				plan, s.opts, s.result, filesByID,
-					plan, s.opts, s.result, filesByID[fileID], fileID, err)
+				plan.filesReferencingBlob(hash), err)
-				if fileErr != nil {
+			if blobErr != nil {
-					return false, fileErr
+				return false, blobErr
-				}
 			}
 
 			// next is among the failed files, so the rest of its blob set
@@ -624,19 +667,19 @@ func (v *Vaultik) restoreProgressTick(
 
 // handleRestoreFileError records a per-file restore failure: fatal unless
 // --skip-errors is set, in which case the file is counted as failed and
-// dropped from the plan.
+// dropped from the plan. A fatal failure is not logged here: the returned
+// error is printed as the command's ERROR: line.
 func (v *Vaultik) handleRestoreFileError(
 	plan *restorePlan, opts *RestoreOptions, result *RestoreResult,
 	file *database.File, fileID types.FileID, err error,
 ) error {
-	log.Error("Failed to restore file", "path", file.Path, "error", err)
-
 	if !opts.SkipErrors {
 		return fmt.Errorf(
 			"restoring %s: %w (pass --skip-errors to continue past "+
 				"restore failures)", file.Path, err)
 	}
 
+	log.Error("Failed to restore file", "path", file.Path, "error", err)
 	v.UI.Errorf("Failed to restore %s: %v. Skipping (--skip-errors).",
 		v.UI.Path(file.Path.String()), err)
 
@@ -648,6 +691,41 @@ func (v *Vaultik) handleRestoreFileError(
 	return nil
 }
 
+// handleRestoreBlobError records a blob that could not be downloaded.
+// fileIDs are the pending files that need it, never empty. Without
+// --skip-errors the first of them fails the restore. With it, the blob is
+// reported once, and its files are counted as failed and dropped from
+// the plan without being reported one by one.
+func (v *Vaultik) handleRestoreBlobError(
+	plan *restorePlan, opts *RestoreOptions, result *RestoreResult,
+	filesByID map[types.FileID]*database.File, fileIDs []types.FileID,
+	err error,
+) error {
+	if !opts.SkipErrors {
+		return v.handleRestoreFileError(
+			plan, opts, result, filesByID[fileIDs[0]], fileIDs[0], err)
+	}
+
+	log.Error("Failed to restore files", "files", len(fileIDs), "error", err)
+	v.UI.Errorf("Failed to restore %d file(s): %v. Skipping them (--skip-errors).",
+		len(fileIDs), err)
+
+	result.BlobsFailed++
+
+	for _, fileID := range fileIDs {
+		path := filesByID[fileID].Path.String()
+
+		log.Debug("Skipped file that needs a failed blob", "path", path)
+
+		result.FilesFailed++
+		result.FilesNeedingFailedBlob = append(result.FilesNeedingFailedBlob, path)
+
+		plan.finishFile(fileID)
+	}
+
+	return nil
+}
+
 // printRestoreProgress emits a periodic restore-phase status line via
 // the UI writer, mirroring scanner.printProcessingProgress so the two
 // long-running commands have the same on-screen rhythm.
@@ -719,8 +797,8 @@ func (v *Vaultik) handleRestoreVerification(
 ) error {
 	// A file that failed to restore was not written and is already
 	// reported as such, so it is not verified.
-	failedToRestore := make(map[string]bool, len(result.FailedFiles))
+	failedToRestore := make(map[string]bool, result.FilesFailed)
-	for _, path := range result.FailedFiles {
+	for _, path := range slices.Concat(result.FailedFiles, result.FilesNeedingFailedBlob) {
 		failedToRestore[path] = true
 	}
 
@@ -754,19 +832,12 @@ func (v *Vaultik) handleRestoreVerification(
 	return nil
 }
 
-// downloadSnapshotDB downloads and decrypts the snapshot metadata
+// downloadSnapshotDB downloads and decrypts the metadata database of the
-// database. The identifier is resolved to the snapshot's remote key: a
+// snapshot at remoteKey, which resolveSnapshotRemoteKey returned for
-// human ID is hashed, and a remote key (or its abbreviation, as printed
+// snapshotID.
-// for a remote-only snapshot) is used as-is, so a host with no local
-// index can restore the snapshots it can only see on the store.
 func (v *Vaultik) downloadSnapshotDB(
-	snapshotID string, identities []age.Identity,
+	snapshotID, remoteKey string, identities []age.Identity,
 ) (*database.DB, string, error) {
-	remoteKey, err := v.resolveSnapshotRemoteKey(snapshotID)
-	if err != nil {
-		return nil, "", err
-	}
-
 	// Download encrypted database from storage
 	dbKey := fmt.Sprintf("metadata/%s/db.zst.age", remoteKey)
 
@@ -783,9 +854,9 @@ func (v *Vaultik) downloadSnapshotDB(
 	// the plaintext to a temp file. Neither the encrypted bytes nor the
 	// decrypted database is ever held whole in memory; a snapshot database
 	// can be large.
-	blobReader, err := blobgen.NewReader(reader, identities...)
+	blobReader, err := v.newSnapshotDBReader(reader, identities)
 	if err != nil {
-		return nil, "", fmt.Errorf("creating decryption reader: %w", err)
+		return nil, "", err
 	}
 
 	defer func() { _ = blobReader.Close() }()

internal/vaultik/restore_locality_test.go

@@ -46,11 +46,11 @@ import (
 //     slice out a few KB — currently the dominant cost in restore.
 //
 // The test deliberately constructs an adversarial scenario: three
-// blobs A/B/C of ~6 MB each, nine files distributed across them, and
+// blobs A/B/C of five 64 KiB chunks each, nine files distributed across
-// path-ordered names that interleave the blobs (a1, b1, c1, a2, b2,
+// them, and path-ordered names that interleave the blobs (a1, b1, c1,
-// c2, …) so naive path-order processing would touch every blob before
+// a2, b2, c2, …) so naive path-order processing would touch every blob
-// finishing any of them.
+// before finishing any of them.
-// localitySource is one 1 MiB fixture file used by the locality test.
+// localitySource is one 64 KiB fixture file used by the locality test.
 type localitySource struct {
 	path string
 	data []byte
@@ -65,10 +65,10 @@ type localityCopy struct {
 
 // localitySourceBytes is the size of each source file of the locality
 // fixture.
-const localitySourceBytes = 1024 * 1024
+const localitySourceBytes = 64 * 1024
 
 // buildLocalityFixture writes the adversarial source layout described
-// in TestRestoreLocalityAndReadAt: 15 sources of 1 MiB each (which the
+// in TestRestoreLocalityAndReadAt: 15 sources of 64 KiB each (which the
 // backup packs into 3 blobs of 5 chunks) plus 9 interleaved-name copies
 // (3 per blob group).
 func buildLocalityFixture(

internal/vaultik/restore_skip_errors_test.go

@@ -51,27 +51,72 @@ func TestRestoreSkipErrorsSkipsFilesOfMissingBlob(t *testing.T) {
 	t.Parallel()
 
 	ctx := context.Background()
-	assertRestoreSkipsLostFiles(ctx, t, backupThenDeleteOneBlob(ctx, t))
+	backup := backupThenDeleteOneBlob(ctx, t)
+	out := assertRestoreSkipsLostFiles(ctx, t, backup)
+
+	assertLostFilesCountedNotListed(t, backup, out)
+}
+
+// TestRestoreSkipErrorsReportsUnreadableBlobOnce restores with SkipErrors
+// after one blob of a two-blob snapshot was overwritten with other bytes
+// of the same size. The blob must be reported once, by its hash, as not a
+// valid age stream, without quoting its bytes, and its files must be
+// counted, not listed.
+func TestRestoreSkipErrorsReportsUnreadableBlobOnce(t *testing.T) {
+	log.Initialize(log.Config{})
+	t.Parallel()
+
+	ctx := context.Background()
+	backup, lostBlob := backupThenOverwriteOneBlob(ctx, t)
+	out := assertRestoreSkipsLostFiles(ctx, t, backup)
+
+	assert.Equal(t, 1, strings.Count(out, "not a valid age stream"), out)
+	assert.Contains(t, out, lostBlob[:16])
+	assert.NotContains(t, out, overwriteBlobPattern)
+	assertLostFilesCountedNotListed(t, backup, out)
 }
 
 // TestRestoreSkipErrorsSkipsFilesWithChunkInNoBlob restores with
 // SkipErrors a snapshot whose metadata lists chunks that no blob holds, as
-// earlier backup defects left behind.
+// earlier backup defects left behind. Each such file fails for its own
+// reason, so each is listed.
 func TestRestoreSkipErrorsSkipsFilesWithChunkInNoBlob(t *testing.T) {
 	log.Initialize(log.Config{})
 	t.Parallel()
 
 	ctx := context.Background()
-	assertRestoreSkipsLostFiles(ctx, t, backupThenDropOneBlobFromMetadata(ctx, t))
+	backup := backupThenDropOneBlobFromMetadata(ctx, t)
+	out := assertRestoreSkipsLostFiles(ctx, t, backup)
+
+	for path := range backup.lost {
+		assert.Containsf(t, out, path, "%s must be reported", path)
+	}
 }
 
-// assertRestoreSkipsLostFiles restores backup with SkipErrors. Every file
+// assertLostFilesCountedNotListed checks that the restore output out
-// stored in the lost blob must be reported as failed and left absent,
+// counts the files of the lost blob and names none of them.
-// every other file must be restored intact, and Restore must still return
+func assertLostFilesCountedNotListed(
-// an error.
+	t *testing.T, backup *missingBlobBackup, out string,
+) {
+	t.Helper()
+
+	assert.Contains(t, out, fmt.Sprintf(
+		"%d of them need a blob that could not be read (1 blob(s) in all)",
+		len(backup.lost)))
+
+	for path := range backup.lost {
+		assert.NotContainsf(t, out, path,
+			"%s needs the lost blob and must be counted, not listed", path)
+	}
+}
+
+// assertRestoreSkipsLostFiles restores backup with SkipErrors and returns
+// what it printed. Every file stored in the lost blob must be left
+// absent, every other file must be restored intact, and Restore must
+// still return an error.
 func assertRestoreSkipsLostFiles(
 	ctx context.Context, t *testing.T, backup *missingBlobBackup,
-) {
+) string {
 	t.Helper()
 
 	var out bytes.Buffer
@@ -93,8 +138,6 @@ func assertRestoreSkipsLostFiles(
 		restored := filepath.Join(backup.restoreDir, path)
 
 		if backup.lost[path] {
-			assert.Containsf(t, out.String(), path,
-				"%s needs the lost blob and must be reported", path)
 			assert.NoFileExists(t, restored)
 
 			continue
@@ -104,6 +147,8 @@ func assertRestoreSkipsLostFiles(
 		require.NoErrorf(t, err, "%s does not need the lost blob", path)
 		assert.Equalf(t, content, got, "%s restored with wrong content", path)
 	}
+
+	return out.String()
 }
 
 // TestRestoreSkipErrorsVerifyChecksOnlyRestoredFiles restores with
@@ -144,9 +189,9 @@ func TestRestoreSkipErrorsVerifyChecksOnlyRestoredFiles(t *testing.T) {
 // TestRestoreSkipErrorsVerifyReportsFailuresApart restores with
 // SkipErrors and Verify after one blob of a two-blob snapshot was
 // deleted, while one file that does restore is written one byte too long.
-// The restore warning must list only the files of the deleted blob, the
+// The restore warning must count the files of the deleted blob without
-// verification summary only the long file, each path once, and Restore
+// listing them, the verification summary must list only the long file,
-// must return an error.
+// once, and Restore must return an error.
 func TestRestoreSkipErrorsVerifyReportsFailuresApart(t *testing.T) {
 	log.Initialize(log.Config{})
 	t.Parallel()
@@ -186,9 +231,9 @@ func TestRestoreSkipErrorsVerifyReportsFailuresApart(t *testing.T) {
 		"Verification failed: 1 files did not match")
 	require.Truef(t, found, "no verification summary in:\n%s", out.String())
 
+	assertLostFilesCountedNotListed(t, backup, warning)
+
 	for path := range backup.lost {
-		assert.Equalf(t, 1, strings.Count(warning, path),
-			"%s must be listed once as failed to restore", path)
 		assert.NotContainsf(t, summary, path,
 			"%s was not restored and must not fail verification", path)
 	}
@@ -292,6 +337,35 @@ func backupThenDeleteOneBlob(
 	return backup
 }
 
+// overwriteBlobPattern repeats, each time followed by a newline, through
+// the bytes that backupThenOverwriteOneBlob writes over a blob. age's own
+// error quotes the data's first line only when it reads a whole line.
+const overwriteBlobPattern = "overwritten-blob-bytes-"
+
+// backupThenOverwriteOneBlob backs up missingBlobFileCount single-chunk
+// files, then overwrites the blob holding the first of them with as many
+// bytes of overwriteBlobPattern lines. It also returns that blob's hash.
+func backupThenOverwriteOneBlob(
+	ctx context.Context, t *testing.T,
+) (*missingBlobBackup, string) {
+	t.Helper()
+
+	backup, db, lostBlob := backupSingleChunkFiles(ctx, t)
+	require.NoError(t, db.Close())
+
+	key := fmt.Sprintf("blobs/%s/%s/%s", lostBlob[:2], lostBlob[2:4], lostBlob)
+
+	info, err := backup.storer.Stat(ctx, key)
+	require.NoError(t, err)
+
+	line := overwriteBlobPattern + "\n"
+	pattern := bytes.Repeat([]byte(line), int(info.Size)/len(line)+1)
+	require.NoError(t, backup.storer.Put(
+		ctx, key, bytes.NewReader(pattern[:info.Size])))
+
+	return backup, lostBlob
+}
+
 // backupThenDropOneBlobFromMetadata backs up missingBlobFileCount
 // single-chunk files, then removes the blob holding the first of them from
 // the snapshot and exports the snapshot metadata again. The exported

internal/vaultik/restore_sweeper_integration_test.go

@@ -27,10 +27,10 @@ import (
 // TestRestoreSweeperEvictsBlobs exercises the reference-counted blob
 // disk cache eviction during restore.
 //
-// The scenario: 30 unique 1 MB random files plus 10 duplicates of those
+// The scenario: 30 unique 128 KiB random files plus 10 duplicates of
-// (40 files total, 30 MB of unique content) get backed up with a 10 MB
+// those (40 files total, 3.75 MiB of unique content) get backed up with
-// blob_size_limit. After backup the snapshot's encrypted blobs are
+// a 1 MiB blob_size_limit. After backup the snapshot's encrypted blobs
-// restored through Vaultik.Restore, and per-key Get counts on the
+// are restored through Vaultik.Restore, and per-key Get counts on the
 // storage layer are recorded. Each blob in the snapshot MUST be
 // downloaded exactly once — re-downloads would mean the sweeper either
 // evicted a blob that was still needed (LRU regression) or that the
@@ -41,7 +41,7 @@ import (
 // original AND every duplicate referencing its chunks have been
 // restored.
 // buildSweeperFixture writes the source layout for the sweeper test: 30
-// unique 1 MB random files plus 10 duplicates of a random subset. The
+// unique 128 KiB random files plus 10 duplicates of a random subset. The
 // PRNG seed is fixed so failures are reproducible; the entropy is what
 // matters here — the FastCDC chunker needs realistic-looking data to
 // pick chunk boundaries naturally. Returns the expected content by
@@ -51,7 +51,7 @@ func buildSweeperFixture(
 ) map[string][]byte {
 	t.Helper()
 
-	const fileSize = 1 * 1024 * 1024
+	const fileSize = 128 * 1024
 
 	rng := rand.New(rand.NewSource(42)) //nolint:gosec // G404: fixture data only
 
@@ -159,7 +159,7 @@ func runSweeperBackup(
 	require.NoError(t, err)
 	require.Equal(t, uniqueFiles+duplicateFiles, scanResult.FilesScanned)
 	require.Greater(t, scanResult.BlobsCreated, 1,
-		"30 MB of unique data at 10 MB blob size should yield multiple blobs")
+		"3.75 MiB of unique data at 1 MiB blob size should yield multiple blobs")
 
 	require.NoError(t, sm.CompleteSnapshot(ctx, snapshotID))
 	require.NoError(t, sm.ExportSnapshotMetadata(ctx, dbPath, snapshotID))
@@ -199,8 +199,8 @@ func TestRestoreSweeperEvictsBlobs(t *testing.T) {
 
 	expected := buildSweeperFixture(t, fs, dataDir, uniqueFiles, duplicateFiles)
 
-	chunkSize := int64(64 * 1024)
+	chunkSize := int64(16 * 1024)
-	maxBlobSize := int64(10 * 1024 * 1024)
+	maxBlobSize := int64(1024 * 1024)
 
 	storer, err := storage.NewFileStorer(storeDir)
 	require.NoError(t, err)

internal/vaultik/restore_wrong_key_test.go

@@ -0,0 +1,161 @@
+package vaultik_test
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"path"
+	"path/filepath"
+	"testing"
+
+	"filippo.io/age"
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/vaultik/internal/blobgen"
+	"sneak.berlin/go/vaultik/internal/config"
+	"sneak.berlin/go/vaultik/internal/log"
+	"sneak.berlin/go/vaultik/internal/snapshot"
+	"sneak.berlin/go/vaultik/internal/ui"
+	"sneak.berlin/go/vaultik/internal/vaultik"
+)
+
+// TestWrongPrivateKeyError checks that restore and deep verify, given a
+// valid private key the backup was not encrypted to, fail with one plain
+// sentence that names where the key was configured.
+func TestWrongPrivateKeyError(t *testing.T) {
+	t.Parallel()
+
+	ctx := context.Background()
+	store := NewMockStorer()
+
+	const snapshotID = "test-host_2026-01-01T00:00:00Z"
+
+	remoteKey := snapshot.RemoteSnapshotKey(snapshotID)
+
+	manifest, err := snapshot.EncodeManifest(
+		&snapshot.Manifest{SnapshotID: remoteKey}, 3)
+	require.NoError(t, err)
+	require.NoError(t, store.Put(ctx,
+		"metadata/"+remoteKey+"/manifest.json.zst", bytes.NewReader(manifest)))
+
+	// The database is encrypted to the test recipient only.
+	var db bytes.Buffer
+
+	writer, err := blobgen.NewWriter(&db, 1, []string{testAgePublicKey})
+	require.NoError(t, err)
+
+	_, err = writer.Write([]byte("snapshot database"))
+	require.NoError(t, err)
+	require.NoError(t, writer.Close())
+	require.NoError(t, store.Put(ctx,
+		"metadata/"+remoteKey+"/db.zst.age", &db))
+
+	otherKey, err := age.GenerateX25519Identity()
+	require.NoError(t, err)
+
+	v := &vaultik.Vaultik{
+		Config:  &config.Config{AgeSecretKey: otherKey.String()},
+		Storage: store,
+		Fs:      afero.NewMemMapFs(),
+		Stdout:  io.Discard,
+		Stderr:  io.Discard,
+		UI:      ui.NewWithColor(io.Discard, false),
+	}
+	v.SetContext(ctx)
+
+	// A Config built directly has no recorded source, so the error names
+	// the config-file field.
+	const want = "cannot decrypt this snapshot: the private key in " +
+		"age_secret_key is not one of the keys the backup was encrypted to"
+
+	err = v.Restore(&vaultik.RestoreOptions{
+		SnapshotID: snapshotID,
+		TargetDir:  t.TempDir(),
+	})
+	require.EqualError(t, err, want)
+
+	err = v.RunDeepVerify(snapshotID, &vaultik.VerifyOptions{Deep: true})
+	require.EqualError(t, err, want)
+}
+
+// TestWrongPrivateKeyForBlobError backs up a file, then backs it up again
+// from an empty local index with a second recipient added. The second
+// snapshot reuses the stored blob, which stays encrypted to the first
+// recipient only. With only the added key configured, restore and deep
+// verify read the database but fail on the blob with one plain sentence
+// that names where the key was configured.
+func TestWrongPrivateKeyForBlobError(t *testing.T) {
+	log.Initialize(log.Config{})
+	t.Parallel()
+
+	fs := afero.NewOsFs()
+	tempDir := t.TempDir()
+	dataDir := filepath.Join(tempDir, "source")
+	dataPath := filepath.Join(dataDir, "data.bin")
+	storeDir := t.TempDir()
+	secondDBPath := filepath.Join(tempDir, "second.sqlite")
+
+	chunkSize := int64(64 * 1024)
+	maxBlobSize := int64(512 * 1024)
+
+	require.NoError(t, fs.MkdirAll(dataDir, 0o755))
+	require.NoError(t, afero.WriteFile(fs, dataPath,
+		bytesPattern("key-", int(chunkSize)), 0o644))
+
+	ctx := context.Background()
+
+	runFileStorageBackup(ctx, t, fs, dataDir, storeDir,
+		filepath.Join(tempDir, "first.sqlite"), chunkSize, maxBlobSize)
+
+	env := setupDedupBackupEnv(
+		ctx, t, fs, storeDir, secondDBPath, chunkSize, maxBlobSize)
+
+	defer func() { _ = env.db.Close() }()
+
+	addedKey, err := age.GenerateX25519Identity()
+	require.NoError(t, err)
+
+	env.cfg.AgeRecipients = append(env.cfg.AgeRecipients,
+		addedKey.Recipient().String())
+
+	snapshotID, result := runDedupSnapshot(ctx, t, env.sm, env.makeScanner(),
+		env.cfg.Hostname, "second", dataDir, secondDBPath)
+	require.Zero(t, result.BlobsUploaded,
+		"the second backup should reuse the stored blob")
+
+	require.NoError(t, env.db.Close())
+
+	blobKeys, err := env.storer.List(ctx, "blobs/")
+	require.NoError(t, err)
+	require.Len(t, blobKeys, 1)
+
+	blobHash := path.Base(blobKeys[0])
+
+	env.cfg.AgeSecretKey = addedKey.String()
+
+	v := &vaultik.Vaultik{
+		Config:  env.cfg,
+		Storage: env.storer,
+		Fs:      fs,
+		Stdout:  io.Discard,
+		Stderr:  io.Discard,
+		UI:      ui.NewWithColor(io.Discard, false),
+	}
+	v.SetContext(ctx)
+
+	const sentence = "cannot decrypt this blob: the private key in " +
+		"age_secret_key is not one of the keys the blob was encrypted to"
+
+	// Restore names the blob by the first 16 characters of its hash.
+	err = v.Restore(&vaultik.RestoreOptions{
+		SnapshotID: snapshotID,
+		TargetDir:  t.TempDir(),
+	})
+	require.EqualError(t, err, "restoring "+dataPath+": downloading blob "+
+		blobHash[:16]+": "+sentence+
+		" (pass --skip-errors to continue past restore failures)")
+
+	err = v.RunDeepVerify(snapshotID, &vaultik.VerifyOptions{Deep: true})
+	require.EqualError(t, err,
+		"blob "+blobHash+" verification failed: "+sentence)
+}

internal/vaultik/snapshot.go

@@ -115,14 +115,9 @@ func (v *Vaultik) CreateSnapshot(opts *SnapshotCreateOptions) error {
 		"index_path", v.Config.IndexPath,
 	)
 
-	err := v.EnsureStorageBinding()
-	if err != nil {
-		return err
-	}
-
 	// Before PruneDatabase: it drops incomplete snapshots, which could
 	// leave the local index without one and so skip the marker check.
-	err = v.markDestination()
+	err := v.markDestination()
 	if err != nil {
 		return err
 	}
@@ -749,7 +744,7 @@ type SnapshotPurgeOptions struct {
 // snapshot name, not the latest globally. This prevents `home` and `system`
 // snapshots from cannibalizing each other.
 func (v *Vaultik) PurgeSnapshotsWithOptions(opts *SnapshotPurgeOptions) error {
-	err := v.EnsureStorageBinding()
+	err := v.checkStorageBinding()
 	if err != nil {
 		return err
 	}
@@ -881,17 +876,12 @@ func (v *Vaultik) confirmAndExecutePurge(
 
 		var confirm string
 
+		// A failure to read the answer means no confirmation.
 		_, err := v.scanStdin(&confirm)
-		if err != nil {
+		if err != nil || strings.ToLower(confirm) != "y" {
 			v.printlnStdout("Cancelled")
 
-			return nil //nolint:nilerr // treat EOF or read error as "no"
+			return ErrNotConfirmed
-		}
-
-		if strings.ToLower(confirm) != "y" {
-			v.printlnStdout("Cancelled")
-
-			return nil
 		}
 	} else if !quiet {
 		v.UI.Infof("The following snapshots will be deleted:")
@@ -969,25 +959,22 @@ func (v *Vaultik) VerifySnapshotWithOptions(
 		Mode:       "shallow",
 	}
 
-	v.printVerifyHeader(snapshotID, opts)
+	// The key is kept so we can also check for the snapshot's encrypted
-
+	// database below.
-	// Resolve the identifier to the snapshot's remote key. A human ID is
-	// hashed; a remote key (or its abbreviation, as printed for a
-	// remote-only snapshot) is used as-is, so a host with no local index
-	// can verify a snapshot it can only see on the store. The key is kept
-	// so we can also check for the snapshot's encrypted database below.
 	remoteKey, err := v.resolveSnapshotRemoteKey(snapshotID)
 	if err != nil {
 		if opts.JSON {
 			result.Status = verifyStatusFailed
-			result.ErrorMessage = fmt.Sprintf("resolving snapshot identifier: %v", err)
+			result.ErrorMessage = err.Error()
 
 			return v.outputVerifyJSON(result)
 		}
 
-		return fmt.Errorf("resolving snapshot identifier: %w", err)
+		return err
 	}
 
+	v.printVerifyHeader(snapshotID, opts)
+
 	manifest, err := v.downloadManifestByKey(remoteKey)
 	if err != nil {
 		if opts.JSON {
@@ -1285,7 +1272,7 @@ func (v *Vaultik) outputVerifyJSON(result *VerifyResult) error {
 // jq` fail (issue #108). The narration is duplicated as log records,
 // which go to stderr and so cannot corrupt the document.
 func (v *Vaultik) CleanupLocalSnapshots(opts *PruneOptions) error {
-	err := v.EnsureStorageBinding()
+	err := v.checkStorageBinding()
 	if err != nil {
 		return err
 	}
@@ -1475,12 +1462,12 @@ func (v *Vaultik) RemoveSnapshot(
 		SnapshotID: snapshotID,
 	}
 
-	err := v.EnsureStorageBinding()
+	err := v.checkStorageBinding()
 	if err != nil {
 		return result, err
 	}
 
-	inLocalIndex, err := v.findSnapshotToRemove(snapshotID, opts)
+	inLocalIndex, err := v.checkSnapshotExists(snapshotID, opts.LocalOnly)
 	if err != nil {
 		return result, err
 	}
@@ -1490,7 +1477,7 @@ func (v *Vaultik) RemoveSnapshot(
 	}
 
 	if !v.confirmRemoveSnapshot(snapshotID, opts) {
-		return result, nil
+		return result, ErrNotConfirmed
 	}
 
 	// Checked before the local record is deleted: it may be the last
@@ -1543,17 +1530,20 @@ func (v *Vaultik) RemoveSnapshot(
 	return result, nil
 }
 
-// findSnapshotToRemove reports whether the local index has a row for
+// checkSnapshotExists returns errSnapshotNotFound when the local index
-// snapshotID, and returns errSnapshotNotFound when there is nothing to
+// has no row for snapshotID and, unless localOnly is set, the
-// remove: no row and, unless LocalOnly is set, no metadata on the
+// destination store has no metadata for it either. inLocalIndex reports
-// destination store either. The destination store is consulted only
+// whether the local index has that row. The destination store is
-// when the local index has no row, so a snapshot in the local index can
+// consulted only when the local index has no row, so a snapshot in the
-// still be removed from it while the destination store is unreachable,
+// local index can still be removed from it while the destination store
-// and only after checkDestinationMarker passes, so an unplugged volume's
+// is unreachable, and only after checkDestinationMarker passes, so an
-// empty mount point is not taken for a store without the snapshot.
+// unplugged volume's empty mount point is not taken for a store without
-func (v *Vaultik) findSnapshotToRemove(
+// the snapshot.
-	snapshotID string, opts *RemoveOptions,
+//
-) (bool, error) {
+//nolint:nonamedreturns // the result name says what the bool means
+func (v *Vaultik) checkSnapshotExists(
+	snapshotID string, localOnly bool,
+) (inLocalIndex bool, err error) {
 	if v.Repositories != nil {
 		snap, err := v.Repositories.Snapshots.GetByID(v.ctx, snapshotID)
 		if err != nil {
@@ -1565,12 +1555,12 @@ func (v *Vaultik) findSnapshotToRemove(
 		}
 	}
 
-	if opts.LocalOnly {
+	if localOnly {
 		return false, fmt.Errorf("%w in the local index: %s",
 			errSnapshotNotFound, snapshotID)
 	}
 
-	err := v.checkDestinationMarker()
+	err = v.checkDestinationMarker()
 	if err != nil {
 		return false, err
 	}
@@ -1712,7 +1702,7 @@ func (v *Vaultik) removeSnapshotRemote(
 // before it removes anything when the destination store cannot be
 // listed or is not present by checkDestinationMarker.
 func (v *Vaultik) RemoveAllSnapshots(opts *RemoveOptions) (*RemoveResult, error) {
-	err := v.EnsureStorageBinding()
+	err := v.checkStorageBinding()
 	if err != nil {
 		return nil, err
 	}

internal/vaultik/snapshot_identifier.go

@@ -28,8 +28,9 @@ var (
 // Two forms are accepted, matching the two things a host can know:
 //
 //   - A human snapshot ID (hostname_name_timestamp), which a host holding
-//     the local index has. It is hashed to its remote key; the store is
+//     the local index has. It is hashed to its remote key. An ID that
-//     not consulted.
+//     names no snapshot in the local index or on the destination store
+//     is an error (see checkSnapshotExists).
 //   - A remote key, or the leading part of one, which is all a host with
 //     no local index can know — it is exactly what `snapshot list` prints
 //     for a remote-only snapshot (see formatRemoteOnlyID). It is resolved
@@ -41,6 +42,11 @@ var (
 // RFC3339 timestamp).
 func (v *Vaultik) resolveSnapshotRemoteKey(identifier string) (string, error) {
 	if !isRemoteKeyOrPrefix(identifier) {
+		_, err := v.checkSnapshotExists(identifier, false)
+		if err != nil {
+			return "", err
+		}
+
 		return snapshot.RemoteSnapshotKey(identifier), nil
 	}
 

internal/vaultik/snapshot_list_test.go

@@ -187,6 +187,17 @@ func (e *listEnv) addRemoteRawTimestamp(
 	t.Helper()
 
 	remoteKey := snapshot.RemoteSnapshotKey(snapshotID)
+	e.putRemoteManifest(t, remoteKey,
+		encodeRemoteManifest(t, remoteKey, timestamp))
+
+	return remoteKey
+}
+
+// encodeRemoteManifest returns the encoded manifest of a one-blob
+// snapshot whose remote key is remoteKey.
+func encodeRemoteManifest(t *testing.T, remoteKey, timestamp string) []byte {
+	t.Helper()
+
 	manifest := &snapshot.Manifest{
 		// Note: the hashed key, never the human ID. That is precisely
 		// why a remote-only snapshot cannot be named.
@@ -202,11 +213,17 @@ func (e *listEnv) addRemoteRawTimestamp(
 	data, err := snapshot.EncodeManifest(manifest, 3)
 	require.NoError(t, err)
 
-	err = e.store.Put(context.Background(),
+	return data
+}
+
+// putRemoteManifest stores an encoded manifest on the destination store
+// under remoteKey.
+func (e *listEnv) putRemoteManifest(t *testing.T, remoteKey string, data []byte) {
+	t.Helper()
+
+	err := e.store.Put(context.Background(),
 		"metadata/"+remoteKey+"/manifest.json.zst", bytes.NewReader(data))
 	require.NoError(t, err)
-
-	return remoteKey
 }
 
 // Fixtures shared across the listing tests.
@@ -345,8 +362,9 @@ func TestSnapshotListAndPurgePrintSizesLikeRemoteInfo(t *testing.T) {
 	// Without --force and with nothing on stdin the purge lists what it
 	// would delete, reads no confirmation, and deletes nothing.
 	env.stdout.Reset()
-	require.NoError(t, env.v.PurgeSnapshotsWithOptions(
+	require.ErrorIs(t, env.v.PurgeSnapshotsWithOptions(
-		&vaultik.SnapshotPurgeOptions{OlderThan: "1d"}))
+		&vaultik.SnapshotPurgeOptions{OlderThan: "1d"}),
+		vaultik.ErrNotConfirmed)
 	assert.Contains(t, findTableRow(t, env.stdout.String(), listLocalID),
 		wantSize, "snapshot purge")
 }
@@ -791,9 +809,17 @@ func TestListSnapshots_JSONReportsTruncation(t *testing.T) {
 
 	timestamp := time.Date(2026, 3, 2, 11, 22, 33, 0, time.UTC)
 
-	// One past the cap, so exactly one snapshot is omitted.
+	// One past the cap, so exactly one snapshot is omitted. The listing
+	// names a snapshot by the key its manifest is stored under, never by
+	// the manifest's own ID. So all of them share one encoded manifest:
+	// encoding 1001 took seconds.
+	data := encodeRemoteManifest(t,
+		snapshot.RemoteSnapshotKey("otherhost_bulk"),
+		timestamp.Format(time.RFC3339))
+
 	for i := range maxRemoteOnlyRowsForTest + 1 {
-		env.addRemote(t, fmt.Sprintf("otherhost_bulk_%04d", i), timestamp)
+		env.putRemoteManifest(t, snapshot.RemoteSnapshotKey(
+			fmt.Sprintf("otherhost_bulk_%04d", i)), data)
 	}
 
 	stderr := captureProcessStderr(t, func() {

internal/vaultik/storage_bind.go

@@ -13,35 +13,30 @@ import (
 var errStorageBindingMismatch = errors.New(
 	"local index is bound to a different backup destination")
 
-// EnsureStorageBinding guarantees that the local index database is
+// checkStorageBinding refuses when the local index database is bound to
-// bound to the currently-configured storage destination. Every mutating
+// a different destination than the configured one, with an error that
-// command must call this before touching either the local index or the
+// tells the user how to recover (revert the config, or run `vaultik
-// destination store, because the two live in lockstep: the local index
+// database delete`). Every mutating command calls it before touching
-// records which chunks/blobs already exist at the destination, and
+// either the local index or the destination store, because the two live
-// mismatched destination + local index produces silent corruption (the
+// in lockstep: the local index records which chunks/blobs already exist
-// scanner sees "known" chunks and skips uploads, then writes snapshots
+// at the destination, and a mismatched pair produces silent corruption
-// whose manifests reference blobs that aren't on the new destination).
+// (the scanner sees "known" chunks and skips uploads, then writes
+// snapshots whose manifests reference blobs that aren't on the new
+// destination).
 //
-// Behaviour:
+// It records nothing. Only a backup binds the local index, through
-//   - On first use (empty stored value), record the configured
+// EnsureStorageBinding, and it does so before adding anything to it. An
-//     destination (storage_url, or the s3.* endpoint, bucket and
+// unbound local index therefore holds nothing from any destination.
-//     prefix) and log the binding.
-//   - When the stored value matches the configured destination, do
-//     nothing and return nil.
-//   - When the two differ, refuse with an error that tells the user
-//     how to recover (revert the config, or run `vaultik database
-//     delete` to discard the local index and rebuild against the new
-//     destination on the next backup).
 //
 // Read-only inspection commands (remote info, snapshot list, etc.)
 // deliberately don't call this: they can be run against a bare
 // destination store without any binding state.
-func (v *Vaultik) EnsureStorageBinding() error {
+func (v *Vaultik) checkStorageBinding() error {
 	if v.Repositories == nil || v.Config == nil {
 		// NewForTesting builds a Vaultik with no DB or config;
-		// there's nothing to bind and no binding to check. Callers
+		// there's no binding to check. Callers exercising the bind
-		// exercising the bind path use a real DB and populate Config
+		// path use a real DB and populate Config explicitly (see
-		// explicitly (see storage_bind_test.go).
+		// storage_bind_test.go).
 		return nil
 	}
 
@@ -50,6 +45,24 @@ func (v *Vaultik) EnsureStorageBinding() error {
 		return err
 	}
 
+	if stored == "" || stored == configured {
+		return nil
+	}
+
+	return fmt.Errorf("%w\n%s",
+		errStorageBindingMismatch, buildBindingMismatchMessage(stored, configured))
+}
+
+// EnsureStorageBinding records the configured destination (storage_url,
+// or the s3.* endpoint, bucket and prefix) as the binding of an unbound
+// local index. It refuses as checkStorageBinding does when the local
+// index is bound to a different destination.
+func (v *Vaultik) EnsureStorageBinding() error {
+	stored, configured, err := v.storageBinding()
+	if err != nil {
+		return err
+	}
+
 	if stored == "" {
 		err = v.Repositories.LocalMeta.Set(
 			v.ctx, database.LocalMetaKeyStorageURL, configured)
@@ -62,14 +75,14 @@ func (v *Vaultik) EnsureStorageBinding() error {
 		return nil
 	}
 
-	if stored == configured {
+	if stored != configured {
-		return nil
-	}
-
 		return fmt.Errorf("%w\n%s",
 			errStorageBindingMismatch, buildBindingMismatchMessage(stored, configured))
 	}
 
+	return nil
+}
+
 // storageBinding returns the destination the local index is bound to
 // ("" when no binding is recorded yet), then the configured destination
 // written the same way. It records nothing, so a read-only command can

internal/vaultik/storage_bind_test.go

@@ -2,6 +2,7 @@ package vaultik_test
 
 import (
 	"context"
+	"path/filepath"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -9,9 +10,126 @@ import (
 	"sneak.berlin/go/vaultik/internal/config"
 	"sneak.berlin/go/vaultik/internal/database"
 	"sneak.berlin/go/vaultik/internal/log"
+	"sneak.berlin/go/vaultik/internal/storage"
+	"sneak.berlin/go/vaultik/internal/storage/faultstore"
 	"sneak.berlin/go/vaultik/internal/vaultik"
 )
 
+// storageBindingOf returns the destination the local index is bound to,
+// or "" when it is not bound.
+func storageBindingOf(
+	ctx context.Context, t *testing.T, repos *database.Repositories,
+) string {
+	t.Helper()
+
+	got, err := repos.LocalMeta.Get(ctx, database.LocalMetaKeyStorageURL)
+	require.NoError(t, err)
+
+	return got
+}
+
+// TestFailedFirstBackupLeavesIndexUnbound checks that a first backup
+// the destination refuses, as a mistyped bucket would, leaves the local
+// index unbound, so a backup with the corrected destination succeeds.
+func TestFailedFirstBackupLeavesIndexUnbound(t *testing.T) {
+	log.Initialize(log.Config{})
+	t.Parallel()
+
+	ctx := context.Background()
+	storeDir := t.TempDir()
+	v, repos := newFileDestinationVaultik(ctx, t, storeDir)
+	working := v.Storage
+
+	refusing := faultstore.New(working)
+	refusing.OnPut = func(string) faultstore.PutAction { return faultstore.PutFail }
+	refusing.OnStat = func(string) bool { return true }
+	v.Storage = refusing
+	v.Config.StorageURL = "file://" + filepath.Join(t.TempDir(), "typo")
+
+	require.ErrorIs(t, backUp(v, "first"), faultstore.ErrInjectedUpload)
+	assert.Empty(t, storageBindingOf(ctx, t, repos))
+
+	v.Storage = working
+	v.Config.StorageURL = "file://" + storeDir
+
+	require.NoError(t, backUp(v, "first"))
+	assert.Equal(t, "file://"+storeDir, storageBindingOf(ctx, t, repos))
+}
+
+// TestBackupToOtherDestinationWritesNoMarker checks that a backup
+// refuses a local index bound to a different destination before it
+// writes the marker to the configured one.
+func TestBackupToOtherDestinationWritesNoMarker(t *testing.T) {
+	log.Initialize(log.Config{})
+	t.Parallel()
+
+	ctx := context.Background()
+	firstDir := t.TempDir()
+	v, _ := newFileDestinationVaultik(ctx, t, firstDir)
+	v.Config.StorageURL = "file://" + firstDir
+
+	require.NoError(t, backUp(v, "first"))
+
+	secondDir := t.TempDir()
+	secondStore, err := storage.NewFileStorer(secondDir)
+	require.NoError(t, err)
+
+	v.Storage = secondStore
+	v.Config.StorageURL = "file://" + secondDir
+
+	require.ErrorContains(t, backUp(v, "first"),
+		"local index is bound to a different backup destination")
+	assert.NoFileExists(t, filepath.Join(secondDir, markerFile))
+}
+
+// TestCommandsOtherThanBackupLeaveIndexUnbound checks that commands
+// other than a backup do not bind an unbound local index, whether or not
+// they fail. Each runs on a fresh local index.
+func TestCommandsOtherThanBackupLeaveIndexUnbound(t *testing.T) {
+	log.Initialize(log.Config{})
+	t.Parallel()
+
+	tests := []struct {
+		name string
+		run  func(v *vaultik.Vaultik) error
+	}{
+		{"prune", func(v *vaultik.Vaultik) error {
+			return v.Prune(&vaultik.PruneOptions{Force: true})
+		}},
+		{"snapshot purge", func(v *vaultik.Vaultik) error {
+			return v.PurgeSnapshotsWithOptions(
+				&vaultik.SnapshotPurgeOptions{KeepLatest: true, Force: true})
+		}},
+		{"snapshot remove", func(v *vaultik.Vaultik) error {
+			_, err := v.RemoveSnapshot("host_first_2026-01-02T03:04:05Z",
+				&vaultik.RemoveOptions{Force: true})
+
+			return err
+		}},
+		{"snapshot remove --all", func(v *vaultik.Vaultik) error {
+			_, err := v.RemoveAllSnapshots(&vaultik.RemoveOptions{Force: true})
+
+			return err
+		}},
+		{"remote nuke", func(v *vaultik.Vaultik) error {
+			return v.NukeRemote(true)
+		}},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			ctx := context.Background()
+			v, repos := newFileDestinationVaultik(ctx, t, t.TempDir())
+
+			_ = tt.run(v)
+
+			assert.Empty(t, storageBindingOf(ctx, t, repos))
+		})
+	}
+}
+
 // buildBindTestVaultik returns a minimal Vaultik wired with a real
 // in-memory DB and a config carrying the given StorageURL. Enough to
 // exercise EnsureStorageBinding without spinning up storage or fx.

internal/vaultik/unknown_snapshot_test.go

@@ -0,0 +1,62 @@
+package vaultik_test
+
+import (
+	"bytes"
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/vaultik/internal/config"
+	"sneak.berlin/go/vaultik/internal/log"
+	"sneak.berlin/go/vaultik/internal/vaultik"
+)
+
+// TestUnknownSnapshotID checks that restore and verify, given an ID that
+// names no snapshot in the local index or on the destination store, say
+// so in the words `snapshot remove` uses and print nothing else.
+func TestUnknownSnapshotID(t *testing.T) {
+	log.Initialize(log.Config{})
+	t.Parallel()
+
+	const unknownID = "host1_home_2026-01-01T00:00:00Z"
+
+	commands := map[string]func(v *vaultik.Vaultik) error{
+		"restore": func(v *vaultik.Vaultik) error {
+			return v.Restore(&vaultik.RestoreOptions{
+				SnapshotID: unknownID,
+				TargetDir:  t.TempDir(),
+			})
+		},
+		"verify": func(v *vaultik.Vaultik) error {
+			return v.VerifySnapshotWithOptions(unknownID, &vaultik.VerifyOptions{})
+		},
+		"verify --deep": func(v *vaultik.Vaultik) error {
+			return v.VerifySnapshotWithOptions(unknownID,
+				&vaultik.VerifyOptions{Deep: true})
+		},
+	}
+
+	for name, run := range commands {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			store := newTestStorer()
+			addManifest(t, store, "snapshot-001", nil)
+
+			// A backup wrote to this destination, so it carries the marker.
+			require.NoError(t, store.Put(context.Background(), markerFile,
+				bytes.NewReader(nil)))
+
+			tv := vaultik.NewForTesting(store)
+			tv.Config = &config.Config{AgeSecretKey: testAgeSecretKey}
+			tv.Repositories = newLocalIndex(t, "snapshot-001")
+
+			err := run(tv.Vaultik)
+
+			require.EqualError(t, err, "snapshot not found in the local "+
+				"index or on the destination store: "+unknownID)
+			assert.Empty(t, tv.Stdout.String())
+		})
+	}
+}

internal/vaultik/vaultik.go

@@ -5,6 +5,7 @@ package vaultik
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -184,6 +185,12 @@ func (v *Vaultik) printlnStdout(args ...any) {
 	_, _ = fmt.Fprintln(v.Stdout, args...)
 }
 
+// ErrNotConfirmed is returned when a confirmation prompt gets any answer
+// but the one it asks for (`y` or `Y`, or `yes` for `database delete`), or
+// stdin ends first. Nothing the prompt asked about is deleted, and the
+// command exits non-zero.
+var ErrNotConfirmed = errors.New("deletion not confirmed")
+
 // scanStdin reads a line of input from stdin.
 func (v *Vaultik) scanStdin(a ...any) (int, error) {
 	return fmt.Fscanln(v.Stdin, a...)

internal/vaultik/verify.go

@@ -120,12 +120,17 @@ func (v *Vaultik) RunDeepVerify(snapshotID string, opts *VerifyOptions) error {
 
 	log.Info("Starting snapshot verification", "snapshot_id", snapshotID, "mode", "deep")
 
+	remoteKey, err := v.resolveSnapshotRemoteKey(snapshotID)
+	if err != nil {
+		return v.deepVerifyFailure(result, opts, err.Error(), err)
+	}
+
 	if !opts.JSON && !v.UI.Quiet() {
 		v.stdoutf("Deep verification of snapshot: %s\n\n", snapshotID)
 	}
 
 	manifest, tempDB, dbBlobs, err := v.loadVerificationData(
-		snapshotID, opts, result, identities)
+		snapshotID, remoteKey, opts, result, identities)
 	if err != nil {
 		return err
 	}
@@ -170,21 +175,13 @@ func (v *Vaultik) RunDeepVerify(snapshotID string, opts *VerifyOptions) error {
 	return nil
 }
 
-// loadVerificationData downloads manifest, database, and blob list for verification
+// loadVerificationData downloads manifest, database, and blob list for
+// verification of the snapshot at remoteKey, which
+// resolveSnapshotRemoteKey returned for snapshotID.
 func (v *Vaultik) loadVerificationData(
-	snapshotID string, opts *VerifyOptions, result *VerifyResult,
+	snapshotID, remoteKey string, opts *VerifyOptions, result *VerifyResult,
 	identities []age.Identity,
 ) (*snapshot.Manifest, *tempDB, []snapshot.BlobInfo, error) {
-	// Resolve the identifier to the snapshot's remote key. A human ID is
-	// hashed; a remote key (or its abbreviation, as printed for a
-	// remote-only snapshot) is used as-is, so a host with no local index
-	// can verify a snapshot it can only see on the store.
-	remoteKey, err := v.resolveSnapshotRemoteKey(snapshotID)
-	if err != nil {
-		return nil, nil, nil, v.deepVerifyFailure(result, opts,
-			fmt.Sprintf("resolving snapshot identifier: %v", err), err)
-	}
-
 	// Download manifest. downloadManifestByKey is the single reader for
 	// remote manifests; see its doc comment.
 	log.Info("Downloading manifest", "remote_key", remoteKey)
@@ -267,6 +264,10 @@ func (v *Vaultik) downloadVerifiedSnapshotDB(
 	defer func() { _ = dbReader.Close() }()
 
 	tdb, err := v.decryptAndLoadDatabase(dbReader, identities)
+	if errors.Is(err, errWrongPrivateKey) {
+		return nil, v.deepVerifyFailure(result, opts, err.Error(), err)
+	}
+
 	if err != nil {
 		return nil, v.deepVerifyFailure(result, opts,
 			fmt.Sprintf("failed to decrypt database: %v", err),
@@ -351,9 +352,9 @@ func (v *Vaultik) decryptAndLoadDatabase(
 	reader io.ReadCloser, identities []age.Identity,
 ) (*tempDB, error) {
 	// Decrypt and decompress through the shared blobgen reader.
-	blobReader, err := blobgen.NewReader(reader, identities...)
+	blobReader, err := v.newSnapshotDBReader(reader, identities)
 	if err != nil {
-		return nil, fmt.Errorf("failed to create decryption reader: %w", err)
+		return nil, err
 	}
 
 	defer func() { _ = blobReader.Close() }()
@@ -426,7 +427,11 @@ func (v *Vaultik) verifyBlob(
 	// the plaintext as it is read. A blob's hash — its remote name — is the
 	// double SHA-256 of that plaintext (see blobgen.DoubleSHA256), not of the
 	// encrypted bytes.
-	blobReader, err := blobgen.NewReader(reader, identities...)
+	blobReader, err := v.newBlobReader(reader, identities)
+	if errors.Is(err, errWrongPrivateKeyForBlob) {
+		return err
+	}
+
 	if err != nil {
 		return fmt.Errorf("failed to create blob reader: %w", err)
 	}

script/version

@@ -11,8 +11,8 @@
 # when no tag is reachable, each with a "-dirty" suffix when tracked
 # files have uncommitted changes. Untracked files are ignored: a stray
 # scratch file does not change what was compiled. Outside a git checkout
-# (release tarball, `go install`), or in one with no commits, it is
+# (such as an unpacked release tarball), or in one with no commits, it
-# "dev".
+# is "dev".
 #
 # Nothing here ever invents a version number.
 set -eu