Allow backing up non-root of volume

docker-compose.yml

@@ -26,9 +26,10 @@ services:
       # Used for determining the health of the container
       - MAX_BACKUP_AGE_SECONDS=86400 # default: 86400 (1d)
     volumes:
-      - /volumes:/source:ro # we backup this folder (which is a BTRFS volume), we mustn't change it, so it's readonly
+      - /:/btrfs-root:ro
       - /volumes/backup:/snapshot # we must mount a path to a folder on the BTRFS disk for the snapshot to be put at, this is just a temporary path
       - /volumes/backup/logs:/backup-logs # we will store the output of the backup commands in this folder
+      
       - borg-cache:/root/.cache/borg # speed up subsequent backups
 
       - health-flag:/health # this is used to determine if the backup was successful and when it was last run

src/backup.sh

@@ -23,13 +23,13 @@ fi
 # we want to stop the script immediately.
 set -e
 
-if [ -d "/snapshot/source" ]; then
-    btrfs subvolume delete /snapshot/source
+if [ -d "/snapshot/btrfs-root" ]; then
+    btrfs subvolume delete /snapshot/btrfs-root
 fi
 
-btrfs subvolume snapshot /source /snapshot
+btrfs subvolume snapshot /btrfs-root /snapshot
 
-cd /snapshot/source
+cd "/snapshot/btrfs-root$BACKUP_RELATIVE_PATH"
 borg create --stats \
     --list \
     --filter=AMCE \
@@ -46,7 +46,7 @@ borg prune --list --stats \
 
 borg compact --threshold=5 --cleanup-commits --verbose --progress
 
-btrfs subvolume delete /snapshot/source
+btrfs subvolume delete /snapshot/btrfs-root
 
 echo "Finished backup script at `date`"
 date > /health/backup_completion_time.log # this used by the healtcheck