Allow backup to be run as non-root user (#366)

* Allow backup to be run as non-root user

* Document usage as non-root user

* Also test /etc access

* Choose better name for doc

Dockerfile

@@ -13,7 +13,8 @@ FROM alpine:3.19
 
 WORKDIR /root
 
-RUN apk add --no-cache ca-certificates
+RUN apk add --no-cache ca-certificates && \
+  chmod a+rw /var/lock
 
 COPY --from=builder /app/cmd/backup/backup /usr/bin/backup
 

docs/how-tos/replace-deprecated-backup-from-snapshot.md

@@ -2,7 +2,7 @@
 title: Replace deprecated BACKUP_FROM_SNAPSHOT usage
 layout: default
 parent: How Tos
-nav_order: 16
+nav_order: 17
 ---
 
 # Replace deprecated `BACKUP_FROM_SNAPSHOT` usage

docs/how-tos/replace-deprecated-backup-stop-container-label.md

@@ -2,7 +2,7 @@
 title: Replace deprecated BACKUP_STOP_CONTAINER_LABEL setting
 layout: default
 parent: How Tos
-nav_order: 19
+nav_order: 20
 ---
 
 # Replace deprecated `BACKUP_STOP_CONTAINER_LABEL` setting

docs/how-tos/replace-deprecated-exec-labels.md

@@ -2,7 +2,7 @@
 title: Replace deprecated exec-pre and exec-post labels
 layout: default
 parent: How Tos
-nav_order: 17
+nav_order: 18
 ---
 
 # Replace deprecated `exec-pre` and `exec-post` labels

docs/how-tos/update-deprecated-email-config.md

@@ -2,7 +2,7 @@
 title: Update deprecated email configuration
 layout: default
 parent: How Tos
-nav_order: 18
+nav_order: 19
 ---
 
 # Update deprecated email configuration

docs/how-tos/use-as-non-root.md

@@ -0,0 +1,36 @@
+---
+title: Use the image as a non-root user
+layout: default
+parent: How Tos
+nav_order: 16
+---
+
+# Use the image as a non-root user
+
+{: .important }
+Running as a non-root user limits interaction with the Docker Daemon.
+If you want to stop and restart containers and services during backup, and the host's Docker daemon is running as root, you will also need to run this tool as root.
+
+By default, this image executes backups using the `root` user.
+In case you prefer to use a different user, you can use Docker's [`user`](https://docs.docker.com/engine/reference/run/#user) option, passing the user and group id:
+
+```console
+docker run --rm \
+  -v data:/backup/data \
+  --env AWS_ACCESS_KEY_ID="<xxx>" \
+  --env AWS_SECRET_ACCESS_KEY="<xxx>" \
+  --env AWS_S3_BUCKET_NAME="<xxx>" \
+  --entrypoint backup \
+  --user 1000:1000 \
+  offen/docker-volume-backup:v2
+```
+
+or in a compose file:
+
+```yml
+services:
+  backup:
+    image: offen/docker-volume-backup:v2
+    user: 1000:1000
+    # further configuration omitted ...
+```

docs/recipes/index.md

@@ -371,3 +371,24 @@ volumes:
   data_1:
   data_2:
 ```
+
+## Running as a non-root user
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:v2
+    user: 1000:1000
+    environment:
+      AWS_S3_BUCKET_NAME: backup-bucket
+      AWS_ACCESS_KEY_ID: AKIAIOSFODNN7EXAMPLE
+      AWS_SECRET_ACCESS_KEY: wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
+    volumes:
+      - data:/backup/my-app-backup:ro
+
+volumes:
+  data:
+```

test/nonroot/01conf.env

@@ -0,0 +1,7 @@
+AWS_ACCESS_KEY_ID="test"
+AWS_SECRET_ACCESS_KEY="GMusLtUmILge2by+z890kQ"
+AWS_ENDPOINT="minio:9000"
+AWS_ENDPOINT_PROTO="http"
+AWS_S3_BUCKET_NAME="backup"
+BACKUP_CRON_EXPRESSION="0 0 5 31 2 ?"
+BACKUP_FILENAME="test.tar.gz"

test/nonroot/docker-compose.yml

@@ -0,0 +1,33 @@
+version: '3'
+
+services:
+  minio:
+    image: minio/minio:RELEASE.2020-08-04T23-10-51Z
+    environment:
+      MINIO_ROOT_USER: test
+      MINIO_ROOT_PASSWORD: test
+      MINIO_ACCESS_KEY: test
+      MINIO_SECRET_KEY: GMusLtUmILge2by+z890kQ
+    entrypoint: /bin/ash -c 'mkdir -p /data/backup && minio server /data'
+    volumes:
+      - ${LOCAL_DIR:-local}:/data
+
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    user: 1000:1000
+    depends_on:
+      - minio
+    restart: always
+    volumes:
+      - app_data:/backup/app_data:ro
+      - ./01conf.env:/etc/dockervolumebackup/conf.d/01conf.env
+
+  offen:
+    image: offen/offen:latest
+    labels:
+      - docker-volume-backup.stop-during-backup=true
+    volumes:
+      - app_data:/var/opt/offen
+
+volumes:
+  app_data:

test/nonroot/run.sh

@@ -0,0 +1,27 @@
+#!/bin/sh
+
+set -e
+
+cd "$(dirname "$0")"
+. ../util.sh
+current_test=$(basename $(pwd))
+
+export LOCAL_DIR=$(mktemp -d)
+
+docker compose up -d --quiet-pull
+sleep 5
+
+docker compose logs backup
+
+# conf.d is used to confirm /etc files are also accessible for non-root users
+docker compose exec backup /bin/sh -c 'set -a; source /etc/dockervolumebackup/conf.d/01conf.env; set +a && backup'
+
+sleep 5
+
+expect_running_containers "3"
+
+if [ ! -f "$LOCAL_DIR/backup/test.tar.gz" ]; then
+  fail "Could not find archive."
+fi
+pass "Archive was created."
+

test/util.sh

@@ -22,7 +22,7 @@ skip () {
 
 expect_running_containers () {
   if [ "$(docker ps -q | wc -l)" != "$1" ]; then
-    fail "Expected $1 containers to be running, instead seen: "$(docker ps -a | wc -l)""
+    fail "Expected $1 containers to be running, instead seen: "$(docker ps -q | wc -l)""
   fi
   pass "$1 containers running."
 }