I'm just testing rollback of a qcow2 # time qm rollback 115 test2 command '/usr/bin/qemu-img snapshot -a test2 /var/lib/vz/images/115/vm-115-disk-1.qcow2' failed: got timeout real 0m1.636s user 0m0.790s sys 0m1.121s using command line directly works fine # /usr/bin/qemu-img snapshot -a test2 /var/lib/vz/images/115/vm-115-disk-1.qcow2