Issue: LXC with Bind Mount forces "Stop" mode and ignores BACKUP_STORAGE configuration

[Ozkovacs]

I am using Ultimate-Updater (version 4.5.2) on a Proxmox VE setup (version 9.1.2).
I noticed that for a specific LXC (ID 101) containing a bind mount (mp0), the script ignores my configuration settings in update.conf and forces a backup in stop mode to a specific NAS storage instead of my local USB storage.

My Configuration (/etc/ultimate-updater/update.conf):

SNAPSHOT="false"
BACKUP="true"
BACKUP_MODE="snapshot"
BACKUP_STORAGE="Backup-local"
BACKUP_LXC_MP="false"

Steps taken to troubleshoot:

1. LXC Config: I modified /etc/pve/lxc/101.conf to add ,backup=0 to the mount point to ensure Proxmox doesn't try to back up the NAS share.
2. Manual Test: Running vzdump 101 --mode snapshot --storage Backup-local manually via CLI works perfectly: the LXC stays online, the mount point is correctly excluded, and the backup goes to the USB drive.
3. The Issue: When running the update command, the script output shows: INFO: starting new backup job: vzdump 101 --mode stop --storage Backup-NAS ... It seems the script hardcodes the --mode stop and overrides the BACKUP_STORAGE variable when it detects a mount point, regardless of the update.conf settings.

Observations:

• The script seems to ignore BACKUP_MODE="snapshot" when an mp is present.
• The script ignores BACKUP_STORAGE="Backup-local" and defaults to another storage (Backup-NAS).
• Even using export BACKUP_MODE="snapshot" before running the script does not change the behavior.

Question: Is this behavior "by design" to ensure maximum data safety for LXCs with mount points, or is it a bug where the script's internal safety checks override the user's explicit configuration?

Here is the output of the update command for this particular LXC:

ℹ  Update only LXC/VM 101 - work only on main host!

🔄 Updating LXC 101 : mssql-server

💾 Start Snapshot and/or Backup
💾 Create a backup for LXC (this will take some time - please wait)
INFO: starting new backup job: vzdump 101 --mode stop --notes-template '{{guestname}} - Ultimate-Updater' --compress zstd --storage Backup-NAS
INFO: Starting Backup of VM 101 (lxc)
INFO: Backup started at 2025-12-19 11:44:06
INFO: status = running
INFO: backup mode: stop
INFO: ionice priority: 7
INFO: CT Name: Zelda
INFO: including mount point rootfs ('/') in backup
INFO: excluding bind mount point mp0 ('/mnt/NAS') from backup (not a volume)
INFO: stopping virtual guest
INFO: creating vzdump archive '/mnt/Proxmox_Bak/dump/vzdump-lxc-101-2025_12_19-11_44_06.tar.zst'
INFO: Total bytes written: 4519188480 (4.3GiB, 41MiB/s)
INFO: archive file size: 2.02GB
INFO: adding notes to backup
INFO: restarting vm
INFO: guest is online again after 114 seconds
INFO: Finished Backup of VM 101 (00:01:54)
INFO: Backup finished at 2025-12-19 11:46:00
INFO: Backup job finished successfully
INFO: notified via target `mail-to-root`
✅ Backup created

Thank you for this great tool!