QEMU does not accept options unrecognized by the block driver in use. Disable locking only for read-only disks that are file-backed, as that's the only block driver it is supported with. Signed-off-by: Lars Seipel <ls(a)slrz.net&gt; --- lib/launch-direct.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/lib/launch-direct.c b/lib/launch-direct.c index 87ac121c7558..678c8c68d59d 100644 --- a/lib/launch-direct.c +++ b/lib/launch-direct.c @@ -260,7 +260,11 @@ add_drive_standard_params (guestfs_h *g, struct backend_direct_data *data, append_list ("cache=unsafe"); if (drv->disk_label) append_list_format ("serial=%s", drv->disk_label); - if (data->qemu_mandatory_locking) + + /* Add the file-specific locking option only for files, as qemu + * won't accept options unknown to the block driver in use. + */ + if (data->qemu_mandatory_locking && drv->src.protocol == drive_protocol_file) append_list ("file.backing.file.locking=off"); } -- 2.14.3