execute QEMU command 'nbd-server-start': Failed to bind socket to ... [Permission denied]

[ENO2019]

[2023-02-08 00:22:39] INFO lib common - printVersion [MainThread]: Version: 1.9.14 Arguments: /usr/bin/virtnbdbackup -d INS-e8evhb8aifmj -l full -o /tmp/backupset
[2023-02-08 00:22:39] INFO root virtnbdbackup - main [MainThread]: Backup level: [full]
[2023-02-08 00:22:39] INFO root virtnbdbackup - main [MainThread]: Libvirt library version: [7000000]
[2023-02-08 00:22:39] INFO virt client - getDomainDisks [MainThread]: Skipping attached [cdrom] device: [hda].
[2023-02-08 00:22:39] INFO root virtnbdbackup - main [MainThread]: Backup will save [1] attached disks.
[2023-02-08 00:22:39] INFO root virtnbdbackup - main [MainThread]: Concurrent backup processes: [1]
[2023-02-08 00:22:39] INFO virt client - redefineCheckpoints [MainThread]: Loading checkpoint list from: [/tmp/backupset/checkpoints]
[2023-02-08 00:22:39] INFO root virtnbdbackup - handleCheckpoints [MainThread]: Checkpoint handling.
[2023-02-08 00:22:39] INFO root virtnbdbackup - handleCheckpoints [MainThread]: Using checkpoint name: [virtnbdbackup.0].
[2023-02-08 00:22:39] INFO root virtnbdbackup - main [MainThread]: Local NDB Endpoint socket: [/var/tmp/virtnbdbackup.51977]
[2023-02-08 00:22:39] INFO root virtnbdbackup - main [MainThread]: Temporary scratch file target directory: [/var/tmp]
[2023-02-08 00:22:39] INFO root virtnbdbackup - startBackupJob [MainThread]: Starting backup job.
[2023-02-08 00:22:39] INFO virt client - fsFreeze [MainThread]: Freezed [1] filesystems.
[2023-02-08 00:22:40] INFO virt client - fsThaw [MainThread]: Thawed [1] filesystems.
[2023-02-08 00:22:40] ERROR root virtnbdbackup - startBackupJob [MainThread]: Failed to start backup: [internal error: unable to execute QEMU command 'nbd-server-start': Failed to bind socket to /var/tmp/virtnbdbackup.51977: Permission denied]

OS: debian 11
libvirtd (libvirt) 7.0.0
virtnbdbackup -V: 1.9.14

[abbbi]

Most probably apparmor causing the issue, search past issues for solution

[abbbi]

see also:

https://github.com/abbbi/virtnbdbackup#backup-fails-with-failed-to-bind-socket-to-vartmpvirtnbdbackupxx-permission-denied