diff --git a/Dockerfile b/Dockerfile
index b4f7273..711588c 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -41,18 +41,15 @@ RUN make build
 # alpine 3.21, 2026-02-28
 FROM alpine@sha256:c3f8e73fdb79deaebaa2037150150191b9dcbfba68b4a46d70103204c53f4709
 
-RUN apk add --no-cache ca-certificates tzdata
+RUN apk add --no-cache ca-certificates tzdata su-exec
 
 COPY --from=builder /src/bin/dnswatcher /usr/local/bin/dnswatcher
+COPY deploy/docker-entrypoint.sh /usr/local/bin/docker-entrypoint.sh
 
-# Run as an unprivileged user that owns the data directory. A fresh named
-# volume inherits this ownership; a bind-mounted host directory must be
-# owned by uid 10001 (see "Running under upaas" in README.md), or startup
-# fails.
+# dnswatcher runs as this unprivileged user. The entrypoint creates the
+# data directory and gives it to this user on every start.
 RUN addgroup -S -g 10001 dnswatcher \
-    && adduser -S -G dnswatcher -u 10001 dnswatcher \
-    && mkdir -p /var/lib/dnswatcher \
-    && chown dnswatcher:dnswatcher /var/lib/dnswatcher
+    && adduser -S -G dnswatcher -u 10001 dnswatcher
 
 ENV DNSWATCHER_DATA_DIR=/var/lib/dnswatcher
 
@@ -62,7 +59,8 @@ ENV DNSWATCHER_DATA_DIR=/var/lib/dnswatcher
 # data directory, or the binary's directory, the working directory.
 WORKDIR /
 
-USER dnswatcher
+# No USER: the entrypoint must start as root to set up the data
+# directory; it then runs dnswatcher as the dnswatcher user.
 
 EXPOSE 8080
 
@@ -72,4 +70,4 @@ EXPOSE 8080
 HEALTHCHECK --interval=10s --timeout=5s --start-period=10s --retries=3 \
     CMD wget -q -O /dev/null "http://127.0.0.1:${PORT:-8080}/.well-known/healthcheck" || exit 1
 
-ENTRYPOINT ["/usr/local/bin/dnswatcher"]
+ENTRYPOINT ["/usr/local/bin/docker-entrypoint.sh"]
diff --git a/README.md b/README.md
index 1e6294b..f971096 100644
--- a/README.md
+++ b/README.md
@@ -533,17 +533,7 @@ repository's `Dockerfile` and runs it. The app needs:
 - **Branch:** `prod`. `prod` is cut from `main`, and merging a `main` to
   `prod` pull request is a deploy.
 - **Volume:** one host directory mounted at `/var/lib/dnswatcher`, where
-  the state file lives. upaas bind-mounts the host path it is given and
-  does not create it. The container runs as uid 10001 and does not start
-  unless it can write there. Create the directory before the first
-  deploy:
-
-  ```sh
-  mkdir -p /path/to/data
-  chown 10001:10001 /path/to/data
-  chmod 700 /path/to/data
-  ```
-
+  the state file lives.
 - **Network and port:** the dashboard is unauthenticated and shows every
   watched name and recent alert, and upaas publishes every mapped port on
   all interfaces of the host
diff --git a/TODO.md b/TODO.md
index 23a1f8f..7462510 100644
--- a/TODO.md
+++ b/TODO.md
@@ -25,6 +25,8 @@ Rationale, Design, TODO, License, Author) if any are still missing.
   constructors: two moved to `export_test.go`, one is deleted (closes #111).
 - 2026-10-01: notify shutdown tests use one timing constant per meaning, name
   the bound they check, and require the drain's debug line (closes #116).
+- 2026-09-29: the entrypoint chowns the data directory to `dnswatcher` and runs
+  dnswatcher as that user, so a host bind mount needs no chown (closes #166).
 - 2026-09-29: the live-DNS test package is renamed `internal/livednstest` and
   added to the `test-support` `deny` list in `.golangci.yml`, so `make lint`
   fails when program code imports it (closes #164).
diff --git a/deploy/docker-entrypoint.sh b/deploy/docker-entrypoint.sh
new file mode 100755
index 0000000..62b95cd
--- /dev/null
+++ b/deploy/docker-entrypoint.sh
@@ -0,0 +1,17 @@
+#!/bin/sh
+# deploy/docker-entrypoint.sh: the Docker image's ENTRYPOINT. It runs as
+# root only to give the data directory to the dnswatcher user: a host
+# directory bind-mounted there keeps its host owner, often root, and may
+# hold a state file left by another uid, which dnswatcher could neither
+# read nor replace. dnswatcher itself always runs as the dnswatcher user.
+set -eu
+
+main() {
+    dir="${DNSWATCHER_DATA_DIR:-/var/lib/dnswatcher}"
+    mkdir -p "$dir"
+    chown -R dnswatcher:dnswatcher "$dir"
+    chmod 700 "$dir"
+    exec su-exec dnswatcher /usr/local/bin/dnswatcher "$@"
+}
+
+main "$@"