unable to execute QEMU agent command 'guest-fsfreeze-freeze': failed to add C:\ to snapshot

[ahmadnassri]

first off, thank you for this great plugin! so much better than any other backup methods!

this might not be an issue with the plugin itself, as I'm successfully able to backup Ubuntu vms using snapshot method!

but in windows, it seems snapshot method fails ...

I tried to google for answers, but I'm not seeing any relevant information.

Windows 10.xml

sent 6,049 bytes received 35 bytes 12,168.00 bytes/sec
total size is 5,939 speedup is 0.98
2021-06-19 12:02:00 information: copy of Windows 10.xml to /mnt/user/backups/Windows 10/20210619_1202_Windows 10.xml complete.
sending incremental file list
c15ed305-5492-a7c9-e457-92e090f81d25_VARS-pure-efi.fd

sent 131,247 bytes received 35 bytes 262,564.00 bytes/sec
total size is 131,072 speedup is 1.00
2021-06-19 12:02:00 information: copy of /etc/libvirt/qemu/nvram/c15ed305-5492-a7c9-e457-92e090f81d25_VARS-pure-efi.fd to /mnt/user/backups/Windows 10/20210619_1202_c15ed305-5492-a7c9-e457-92e090f81d25_VARS-pure-efi.fd complete.
2021-06-19 12:02:00 information: able to perform snapshot for disk /mnt/user/domains/Windows 10/vdisk1.img on Windows 10. use_snapshots is 1. vm_state is running. vdisk_type is raw
2021-06-19 12:02:00 information: qemu agent found. enabling quiesce on snapshot.
error: internal error: unable to execute QEMU agent command 'guest-fsfreeze-freeze': failed to add C:\ to snapshot set:

2021-06-19 12:02:00 failure: snapshot command failed on vdisk1.snap for Windows 10.
2021-06-19 12:02:00 failure: snapshot_fallback is 0. skipping backup for Windows 10 to prevent data loss. no cleanup will be performed for this vm.
2021-06-19 12:02:00 information: Ubuntu can be found on the system. attempting backup.
2021-06-19 12:02:00 information: creating local Ubuntu.xml to work with during backup.
2021-06-19 12:02:00 information: /mnt/user/backups/Ubuntu exists. continuing.
2021-06-19 12:02:00 information: skip_vm_shutdown is false and use_snapshots is 1. skipping vm shutdown procedure. Ubuntu is running. can_backup_vm set to y.
2021-06-19 12:02:00 information: actually_copy_files is 1.
2021-06-19 12:02:00 information: can_backup_vm flag is y. starting backup of Ubuntu configuration, nvram, and vdisk(s).
sending incremental file list

I can confirm qemu agent is installed and running:

any advise on where the issue might be?