fix(vaultwarden): make backup script filesystem-agnostic for NTFS/exFAT

- Replace symbolic link handling with a latest.txt file pointer
- Trade hard-link deduplication for universal drive compatibility
- Guarantee complete standalone backups across all target filesystems

vaultwarden_backup.sh

@@ -3,8 +3,9 @@
 # ==============================================================================
 # Script: vaultwarden_backup.sh
 # Description: Backs up Vaultwarden to timestamped directories on a mounted 
-#              drive using Docker exec and rsync. Utilizes hard links for 
-#              deduplication and automatically prunes backups older than RETENTION_DAYS.
+#              drive using Docker exec and rsync. Compatible with non-POSIX 
+#              filesystems (exFAT, NTFS, FAT32) and automatically prunes 
+#              backups older than RETENTION_DAYS.
 # Usage:       sudo ./vaultwarden_backup.sh
 # Notes:       Must be run with root/sudo privileges.
 # ==============================================================================
@@ -22,7 +23,7 @@ RETENTION_DAYS=30
 # Timestamp and Folder Setup
 TIMESTAMP=$(date +"%Y-%m-%d_%H%M%S")
 CURRENT_BACKUP_DIR="$VAULTWARDEN_DESTINATION/backup_$TIMESTAMP"
-LATEST_LINK="$VAULTWARDEN_DESTINATION/latest"
+LATEST_TXT_FILE="$VAULTWARDEN_DESTINATION/latest.txt"
 
 # ntfy Notification Configuration
 NTFY_TOPIC="Server"
@@ -54,7 +55,7 @@ if ! docker ps --format '{{.Names}}' | grep -q "^${CONTAINER_NAME}$"; then
     exit 1
 fi
 
-# Create target directories if they don't exist
+# Create target directory for current run
 mkdir -p "$CURRENT_BACKUP_DIR"
 
 # ==============================================================================
@@ -97,13 +98,15 @@ if [ $RSYNC_DB_STATUS -ne 0 ]; then
     exit 1
 fi
 
-# Step 3: Rsync remaining data (using --link-dest for storage efficiency if 'latest' exists)
-echo "Rsyncing attachments, RSA keys, and configuration files..."
+# Step 3: Find previous backup directory for --link-dest (if filesystem supports it)
+PREVIOUS_BACKUP_DIR=$(ls -td "$VAULTWARDEN_DESTINATION"/backup_* 2>/dev/null | grep -v "$CURRENT_BACKUP_DIR" | head -n 1)
+
 LINK_DEST_PARAM=""
-if [ -d "$LATEST_LINK" ]; then
-    LINK_DEST_PARAM="--link-dest=$LATEST_LINK"
+if [ -n "$PREVIOUS_BACKUP_DIR" ] && [ -d "$PREVIOUS_BACKUP_DIR" ]; then
+    LINK_DEST_PARAM="--link-dest=$PREVIOUS_BACKUP_DIR"
 fi
 
+echo "Rsyncing attachments, RSA keys, and configuration files..."
 rsync -av --no-owner --no-group $LINK_DEST_PARAM --exclude='db.sqlite3*' "$VAULTWARDEN_DATA_DIR/" "$CURRENT_BACKUP_DIR/"
 RSYNC_DATA_STATUS=$?
 
@@ -113,9 +116,8 @@ if [ $RSYNC_DATA_STATUS -ne 0 ]; then
     exit 1
 fi
 
-# Step 4: Update 'latest' symlink to point to this new backup folder
-rm -f "$LATEST_LINK"
-ln -s "$CURRENT_BACKUP_DIR" "$LATEST_LINK"
+# Step 4: Record current backup path to latest.txt
+echo "$CURRENT_BACKUP_DIR" > "$LATEST_TXT_FILE"
 
 # ==============================================================================
 # Retention Cleanup (Prune Backups Older than RETENTION_DAYS)