INC/DIFF mode for offline VMs

[x09]

I want backup OFFLINE VMs. Documentaions talks about copy, inc/diff modes.
But i can use 'copy' mode only. How use inc/diff ?

If the virtual domain is not in running state (powered off) virtnbdbackup supports copy and inc/diff backup modes. Incremental and differential backups will then save the changed blocks since last created checkpoint.

First backup, set full (but switch to copy after)

[anton@dell virtnbdbackup]$sudo virtnbdbackup -d MySuperServer -l full  -o /mnt/usb/WD/kvmbackup/virt/MySuperServer
[2024-08-02 13:07:59] INFO lib common - printVersion [main]:  Version: 2.11 Arguments: /usr/bin/virtnbdbackup -d MySuperServer -l full -o /mnt/usb/WD/kvmbackup/virt/MySuperServer
[2024-08-02 13:07:59] INFO root virtnbdbackup - main [main]:  Backup level: [full]
[2024-08-02 13:07:59] INFO root virtnbdbackup - main [main]:  Libvirt library version: [9007000]
[2024-08-02 13:07:59] INFO root virtnbdbackup - main [main]:  NBD library version: [1.19.11]
[2024-08-02 13:07:59] WARNING root check - vmstate [main]:  Domain is offline, resetting backup options.
[2024-08-02 13:07:59] WARNING root check - vmstate [main]:  New Backup level: [copy].
[2024-08-02 13:07:59] INFO root disktype - Optical [main]:  Skipping attached [cdrom] device: [sda].
[2024-08-02 13:07:59] INFO root virtnbdbackup - main [main]:  Backup will save [1] attached disks.
[2024-08-02 13:07:59] INFO root virtnbdbackup - main [main]:  Concurrent backup processes: [1]
[2024-08-02 13:07:59] INFO root checkpoint - create [main]:  Loading checkpoints from: [/mnt/usb/WD/kvmbackup/virt/MySuperServer/MySuperServer.cpt]
[2024-08-02 13:07:59] INFO root checkpoint - create [main]:  Checkpoint handling.
[2024-08-02 13:07:59] INFO root virtnbdbackup - main [main]:  Local NBD Endpoint socket: [/var/tmp/virtnbdbackup.1641206]
[2024-08-02 13:07:59] INFO root server - setup [vda]:  Offline backup, starting local NBD server, socket: [/var/tmp/virtnbdbackup.1641206.vda]
[2024-08-02 13:07:59] INFO root server - setup [vda]:  Local NBD Service started, PID: [1641212]
[2024-08-02 13:07:59] INFO nbd client - connect [vda]:  Waiting until NBD server at [nbd+unix:///vda?socket=/var/tmp/virtnbdbackup.1641206.vda] is up.
[2024-08-02 13:08:00] INFO nbd client - connect [vda]:  Connection to NBD backend succeeded.
[2024-08-02 13:08:00] INFO root disk - backup [vda]:  Got 660 extents to backup.
[2024-08-02 13:08:00] INFO root disk - backup [vda]:  21474836480 bytes disk size
[2024-08-02 13:08:00] INFO root disk - backup [vda]:  19999227904 bytes of data extents to backup
[2024-08-02 13:08:00] INFO root target - get [vda]:  Write data to target file: [/mnt/usb/WD/kvmbackup/virt/MySuperServer/vda.copy.data.partial].
[2024-08-02 13:08:00] INFO root disk - backup [vda]:  Creating thin provisioned stream backup image
[2024-08-02 13:11:25] INFO root disk - backup [vda]:  Stopping NBD Service.                                                                                  
[2024-08-02 13:11:25] INFO root metadata - backupChecksum [vda]:  Checksum for file: [/mnt/usb/WD/kvmbackup/virt/MySuperServer/vda.copy.data]:[1775409437]
[2024-08-02 13:11:25] INFO root metadata - backupChecksum [vda]:  Saving checksum to: [/mnt/usb/WD/kvmbackup/virt/MySuperServer/vda.copy.data.chksum]
[2024-08-02 13:11:25] INFO root metadata - backupConfig [main]:  Saving VM config to: [/mnt/usb/WD/kvmbackup/virt/MySuperServer/vmconfig.copy.xml]
[2024-08-02 13:11:25] INFO root metadata - backupDiskInfo [main]:  Saved qcow image config to: [/mnt/usb/WD/kvmbackup/virt/MySuperServer/vda.copy.qcow.json]
[2024-08-02 13:11:25] INFO root virtnbdbackup - main [main]:  Total saved disk data: [18.6GB]
[2024-08-02 13:11:25] INFO root virtnbdbackup - main [main]:  Finished successfully

Then, i try 'inc' mode, but get 'No full backup'. why?

[anton@dell virtnbdbackup]$ sudo virtnbdbackup -d MySuperServer -l inc  -o /mnt/usb/WD/kvmbackup/virt/MySuperServer
[2024-08-02 13:12:56] INFO lib common - printVersion [main]:  Version: 2.11 Arguments: /usr/bin/virtnbdbackup -d MySuperServer -l inc -o /mnt/usb/WD/kvmbackup/virt/MySuperServer
[2024-08-02 13:12:56] INFO root virtnbdbackup - main [main]:  Backup level: [inc]
[2024-08-02 13:12:56] INFO root virtnbdbackup - main [main]:  Libvirt library version: [9007000]
[2024-08-02 13:12:56] INFO root virtnbdbackup - main [main]:  NBD library version: [1.19.11]
[2024-08-02 13:12:56] ERROR root virtnbdbackup - main [main]:  Unable to execute [inc] backup: No full backup found in target directory: [/mnt/usb/WD/kvmbackup/virt/MySuperServer]

At next, try 'diff', and 'No full backup' again..

[anton@dell virtnbdbackup]$ sudo virtnbdbackup -d MySuperServer -l diff  -o /mnt/usb/WD/kvmbackup/virt/MySuperServer
[2024-08-02 13:13:04] INFO lib common - printVersion [main]:  Version: 2.11 Arguments: /usr/bin/virtnbdbackup -d MySuperServer -l diff -o /mnt/usb/WD/kvmbackup/virt/MySuperServer
[2024-08-02 13:13:04] INFO root virtnbdbackup - main [main]:  Backup level: [diff]
[2024-08-02 13:13:04] INFO root virtnbdbackup - main [main]:  Libvirt library version: [9007000]
[2024-08-02 13:13:04] INFO root virtnbdbackup - main [main]:  NBD library version: [1.19.11]
[2024-08-02 13:13:04] ERROR root virtnbdbackup - main [main]:  Unable to execute [diff] backup: No full backup found in target directory: [/mnt/usb/WD/kvmbackup/virt/MySuperServer]

And last, AUTO mode

[anton@dell virtnbdbackup]$ sudo virtnbdbackup -d MySuperServer -l auto -o /mnt/usb/WD/kvmbackup/virt/MySuperServer
[2024-08-02 14:11:37] INFO lib common - printVersion [main]:  Version: 2.11 Arguments: /usr/bin/virtnbdbackup -d MySuperServer -l auto -o /mnt/usb/WD/kvmbackup/virt/MySuperServer
[2024-08-02 14:11:37] INFO root virtnbdbackup - main [main]:  Backup level: [auto]
[2024-08-02 14:11:37] INFO root virtnbdbackup - main [main]:  Libvirt library version: [9007000]
[2024-08-02 14:11:37] INFO root virtnbdbackup - main [main]:  NBD library version: [1.19.11]
[2024-08-02 14:11:37] ERROR root virtnbdbackup - main [main]:  Can't execute switch to auto incremental backup: specified target folder [/mnt/usb/WD/kvmbackup/virt/MySuperServer] does not contain full backup.
[anton@dell virtnbdbackup]$ 

what i do wrong?

[anton@dell virtnbdbackup]$ ll /mnt/usb/WD/kvmbackup/virt/MySuperServer
итого 19530584
-rw-r--r-- 1 root  root          671 авг  2 14:11 backup.auto.08022024141137.log
drwxr-xr-x 3 root  root         4096 авг  2 14:11 ./
-rw-r--r-- 1 root  root          764 авг  2 14:10 backup.full.08022024141059.log
-rw-r--r-- 1 root  root          643 авг  2 13:13 backup.diff.08022024131304.log
-rw-r--r-- 1 root  root          640 авг  2 13:12 backup.inc.08022024131256.log
-rw-r--r-- 1 root  root         3161 авг  2 13:11 backup.full.08022024130759.log
-rw-r--r-- 1 root  root         1302 авг  2 13:11 vda.copy.qcow.json
-rw-r--r-- 1 root  root         6129 авг  2 13:11 vmconfig.copy.xml
-rw-r--r-- 1 root  root           10 авг  2 13:11 vda.copy.data.chksum
-rw-r--r-- 1 root  root  19999255377 авг  2 13:11 vda.copy.data
-rw-r--r-- 1 root  root          643 авг  2 13:07 backup.diff.08022024130752.log
-rw-r--r-- 1 root  root          640 авг  2 13:07 backup.inc.08022024130748.log
drwxr-xr-x 2 root  root         4096 авг  2 13:07 checkpoints/
drwxr-xr-x 3 anton anton        4096 авг  2 13:07 ../

[anton@dell virtnbdbackup]$ virtnbdbackup --version
2.11

[abbbi]

By default libvirt does not allow to take full/inc/diff backups for shutdown virtual machines because that requires the qemu process for the VM to be executed, You can use option -S to start VM in paused mode for full/inc/diff backups.

The VM process will then be started with cpu's disabled (nothing will be executed) but the qemu process that is required for inc/diff backups is spawned and exits after backup finishes.

Without option -S full backup will fallback to copy backup which cannot be used for further incremental backups, thus subsequent auto/inc/diff backups wont work on a target directory which includes only type copy backup.

See also:
https://github.com/abbbi/virtnbdbackup?tab=readme-ov-file#backing-up-offline-virtual-domains