Add limitations section to README

README.md

@@ -322,6 +322,35 @@ See `config.example.yml` for a complete annotated example. Key fields:
 
 ---
 
+## limitations
+
+* **No extended attributes (xattrs).** ACLs, macOS Finder metadata,
+  quarantine flags, SELinux labels, and other extended attributes are not
+  backed up or restored.
+* **No hard link detection.** Two hard links to the same inode are backed
+  up as independent files. Content deduplication means the data is stored
+  once, but the hard link relationship is lost on restore.
+* **No sparse file support.** Sparse files are fully materialized during
+  backup. A 100 GB sparse VM disk that is mostly zeros will consume the
+  full (compressed) size in storage.
+* **No bandwidth limiting.** Uploads and downloads use whatever bandwidth
+  is available. There is no `--bwlimit` flag yet.
+* **No parallel blob downloads during restore.** Blobs are fetched
+  sequentially. Restore speed is bound by single-stream throughput.
+* **Device nodes, named pipes, and sockets are silently skipped.** Only
+  regular files, directories, and symlinks are backed up.
+* **No database migrations.** If the local SQLite schema changes between
+  versions, delete the local database (`vaultik database purge`) and run
+  a full backup. Remote storage is unaffected.
+* **Files that change during backup may be inconsistent.** There is no
+  filesystem snapshot or freeze. If a file is modified between the scan
+  and chunk phases, the backed-up copy may reflect a partial write.
+* **Ownership restoration requires root.** File uid/gid are recorded
+  and restored, but `chown` requires elevated privileges. Without root,
+  files are restored with the current user's ownership.
+
+---
+
 ## roadmap
 
 Items for future releases: