Debug option --printonly make backup in auto mode

[sikorapatryk]

Version used 2.10

Describe the bug Invoking a command: virtnbdbackup --printonly -d vm01 -l auto -o /backup/vm01/$(date +"%Y/%U") --scratchdir /backup/vm01 -i vda --freeze-mountpoint / --noprogress --compress --nocolor when the target folder -o /backup/vm01/$(date +"%Y/%U") is empty causes the full backup to be started.

Expected behavior Information about the size of the full backup or a warning that there is no backup in the target location yet should be displayed.

Hypervisor information:

• OS: Red Hat Enterprise Linux 9.3 (Plow)
• HV type: libvirt-10.0.0-6.3.el9_4.x86_64 qemu-kvm-8.0.0-16.el9_3.3.x86_64

[abbbi]

hi,

--printonly can only work if there is already an checkpoint existant, to estimate the backup size of an incremental or differencial backup, so it requires an full backup beforehand. The check involves if there is an parent checkpoint:

if args.printonly and args.cpt.parent and not args.offline:

args.cpt.parent doesnt exist in this case thus its executing an backup.

The function cant estimate the size of a full backup, only the size of an incremental or a differential backup. I think behavior is OK for auto backup function: its better to create an backup than not in this case.

Updated README to be more specific.

Thanks