fix: container permissions and volume setup

Problems fixed:
- archivum user (UID 1000) could not write to bind-mounted /config or /data
  because Docker (especially on Windows/WSL2) creates volumes owned by root
- /data/wiki and /data/db subdirectories were never created, causing
  "no such file or directory" when the app tried to write files

Changes:
- docker/entrypoint.sh: runs as root, creates /config /data/wiki /data/db,
  chowns them to PUID:PGID, then drops privileges via su-exec
- Dockerfile: install su-exec + git, copy entrypoint, remove build-time
  USER directive (privilege drop happens at runtime via entrypoint)
- docker-compose.yml: switch local dev to named volumes so Docker manages
  ownership automatically (avoids Windows/WSL2 bind-mount permission issues);
  add TZ env var; explicit comments on how to switch to bind mounts

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker/Dockerfile

@@ -12,8 +12,9 @@ FROM golang:1.22-alpine AS backend-builder
 
 WORKDIR /app/backend
 # Copy go.mod first for layer caching. go.sum is written by go mod download
-# when it doesn't exist yet (skeleton project), or verified when it does.
+# when it doesn't exist yet, or verified when it does.
 COPY backend/go.mod ./
+COPY backend/go.su[m] ./
 RUN go mod download -x
 COPY backend/ ./
 # CGO disabled — pure Go SQLite (modernc.org/sqlite).
@@ -22,23 +23,30 @@ RUN CGO_ENABLED=0 go build -ldflags="-s -w" -o /archivum ./cmd/server
 # ── Stage 3: Runtime image ────────────────────────────────────────────────────
 FROM alpine:3.20
 
-# Allow PUID/PGID override at runtime.
-ARG PUID=1000
-ARG PGID=1000
+# su-exec: lightweight tool to drop privileges (replaces gosu / setpriv).
+# git: needed for wiki commit operations.
+RUN apk add --no-cache su-exec git
 
-RUN addgroup -g "${PGID}" archivum \
- && adduser -u "${PUID}" -G archivum -s /sbin/nologin -D archivum
+# Create the app group and user that the entrypoint will run as.
+# PUID/PGID can be overridden at runtime via environment variables;
+# the entrypoint script uses them rather than these build-time values.
+RUN addgroup -g 1000 archivum \
+ && adduser -u 1000 -G archivum -s /sbin/nologin -D archivum
 
-# Embed frontend into the binary's working directory.
-COPY --from=frontend-builder /app/frontend/dist /srv/archivum/ui
-COPY --from=backend-builder  /archivum            /usr/local/bin/archivum
+COPY --from=frontend-builder /app/frontend/dist    /srv/archivum/ui
+COPY --from=backend-builder  /archivum              /usr/local/bin/archivum
+COPY docker/entrypoint.sh                           /usr/local/bin/entrypoint.sh
+RUN chmod +x /usr/local/bin/entrypoint.sh
 
-# Volumes: config and data live outside the image.
+# Declare the volume mount points. The entrypoint creates subdirectories
+# and fixes ownership before the application starts.
 VOLUME ["/config", "/data"]
 
-ENV DOCKER_PATH=/config
+ENV DOCKER_PATH=/config \
+    UI_DIR=/srv/archivum/ui \
+    PUID=1000 \
+    PGID=1000
 
-USER archivum
+# Entrypoint runs as root so it can chown the volumes, then drops to PUID:PGID.
 EXPOSE 4000
-
-ENTRYPOINT ["/usr/local/bin/archivum"]
+ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]

docker/docker-compose.yml

@@ -8,10 +8,28 @@ services:
     restart: unless-stopped
     ports:
       - "8080:4000"
-    volumes:
-      - ${DOCKER_PATH:-./data}/config:/config
-      - ${DOCKER_PATH:-./data}/data:/data
+
     environment:
+      # Points to the config directory inside the container.
       DOCKER_PATH: /config
+      UI_DIR: /srv/archivum/ui
+      # Set to match the owner of the host directories (run `id` to check).
       PUID: ${PUID:-1000}
       PGID: ${PGID:-1000}
+      TZ: ${TZ:-Europe/Stockholm}
+
+    volumes:
+      # Configuration (config.json written here by Setup Wizard).
+      - archivum-config:/config
+      # All data: wiki files live in /data/wiki, SQLite db in /data/db.
+      # Using named volumes for local dev avoids Windows/WSL2 permission issues.
+      - archivum-data:/data
+
+# Named volumes let Docker manage ownership automatically.
+# Replace with bind mounts if you need direct host access:
+#   - ./local/config:/config
+#   - ./local/data:/data
+# (and make sure the host directories are owned by PUID:PGID)
+volumes:
+  archivum-config:
+  archivum-data:

docker/entrypoint.sh

@@ -0,0 +1,28 @@
+#!/bin/sh
+# Archivum container entrypoint
+# Runs as root, creates directories, fixes permissions, then drops to PUID:PGID.
+set -e
+
+PUID="${PUID:-1000}"
+PGID="${PGID:-1000}"
+
+echo "[entrypoint] starting as uid=$(id -u) gid=$(id -g)"
+echo "[entrypoint] target PUID=${PUID} PGID=${PGID}"
+
+# ── Ensure required directories exist ──────────────────────────────────────
+mkdir -p /config
+mkdir -p /data/wiki
+mkdir -p /data/db
+
+# ── Fix ownership so the app user can read/write all volumes ───────────────
+# This is needed because:
+#   - bind-mounted directories from the host may be owned by root
+#   - Docker Desktop on Windows mounts volumes with host permissions
+#     that don't map to the container user
+chown -R "${PUID}:${PGID}" /config /data
+
+echo "[entrypoint] /config and /data ownership set to ${PUID}:${PGID}"
+
+# ── Drop privileges and exec the application ───────────────────────────────
+echo "[entrypoint] exec archivum as ${PUID}:${PGID}"
+exec su-exec "${PUID}:${PGID}" /usr/local/bin/archivum "$@"