Enable pre and post commands

README.md

@@ -228,6 +228,8 @@ Variable | Default | Notes
 `BACKUP_CRON_EXPRESSION` | `@daily` | Standard debian-flavored `cron` expression for when the backup should run. Use e.g. `0 4 * * *` to back up at 4 AM every night. See the [man page](http://man7.org/linux/man-pages/man8/cron.8.html) or [crontab.guru](https://crontab.guru/) for more.
 `BACKUP_FILENAME` | `backup-%Y-%m-%dT%H-%M-%S.tar.gz` | File name template for the backup file. Is passed through `date` for formatting. See the [man page](http://man7.org/linux/man-pages/man1/date.1.html) for more.
 `BACKUP_ARCHIVE` | `/archive` | When this path is available within the container (i.e. you've mounted a Docker volume there), a finished backup file will get archived there after each run.
+`PRE_COMMAND` |  | Commands that is executed before the backup is transferred to `/archive`.
+`POST_COMMAND` |  | Commands that is executed after the backup has been transferred to `/archive`.
 `BACKUP_UID` | `root (0)` | After backup file has been moved to archive location the file user ownership is changed to this UID.
 `BACKUP_GID` | `$BACKUP_UID` | After backup file has been moved to archive location the file group ownership is changed to this GID.
 `BACKUP_WAIT_SECONDS` | `0` | The backup script will sleep this many seconds between re-starting stopped containers, and proceeding with archiving/uploading the backup. This can be useful if you don't want the load/network spike of a large upload immediately after the load/network spike of container startup.

src/backup.sh

@@ -133,10 +133,18 @@ fi
 
 if [ -d "$BACKUP_ARCHIVE" ]; then
   info "Archiving backup"
+  if [ ! -z "$PRE_COMMAND" ]; then
+    echo "Pre command: $PRE_COMMAND"
+    $PRE_COMMAND
+  fi
   mv -v "$BACKUP_FILENAME" "$BACKUP_ARCHIVE/$BACKUP_FILENAME"
   if (($BACKUP_UID > 0)); then
     chown -v $BACKUP_UID:$BACKUP_GID "$BACKUP_ARCHIVE/$BACKUP_FILENAME"
   fi
+  if [ ! -z "$POST_COMMAND" ]; then
+    echo "Post command: $POST_COMMAND"
+    $POST_COMMAND
+  fi
 fi
 
 if [ -f "$BACKUP_FILENAME" ]; then

src/entrypoint.sh

@@ -10,6 +10,8 @@ BACKUP_CRON_EXPRESSION="${BACKUP_CRON_EXPRESSION:-@daily}"
 AWS_S3_BUCKET_NAME="${AWS_S3_BUCKET_NAME:-}"
 AWS_GLACIER_VAULT_NAME="${AWS_GLACIER_VAULT_NAME:-}"
 AWS_EXTRA_ARGS="${AWS_EXTRA_ARGS:-}"
+PRE_COMMAND="${PRE_COMMAND:-}"
+POST_COMMAND="${POST_COMMAND:-}"
 SCP_HOST="${SCP_HOST:-}"
 SCP_USER="${SCP_USER:-}"
 SCP_DIRECTORY="${SCP_DIRECTORY:-}"

test/pre-post-command/docker-compose.yml

@@ -0,0 +1,23 @@
+version: "3"
+
+services:
+
+  dashboard:
+    image: grafana/grafana:7.4.5
+    volumes:
+      - grafana-data:/var/lib/grafana           # This is where Grafana keeps its data
+
+  backup:
+    build: ../..
+    environment:
+      # Commands that is executed before the backup is transferred:
+      PRE_COMMAND: "ls -la /archive"
+      # Command that is executed after the backup has been transferred:
+      # "Delete all files in /archive that are older than seven days."
+      POST_COMMAND: "rm $$(find /archive/* -mtime +7)"
+    volumes:
+      - grafana-data:/backup/grafana-data:ro    # Mount the Grafana data volume (as read-only)
+      - /home/pi/backups:/archive               # Mount the directory where the backups are being stored
+
+volumes:
+  grafana-data: