Hello, Using older libguestfs 1.34.6-2 (from Ubuntu's standard package), I encountered this: libguestfs fails with an error, but the error code is "success": $ sudo guestmount -m /dev/sda1 --ro \ -o allow_others \ -a data.qcow2 \ /media/foo fuse: unknown option `allow_others' libguestfs: error: fuse_new: /media/foo/: Success Other fuse errors also cause the same behavior, e.g. mounting to an already-mounted directory: $ sudo guestmount -m /dev/sda1 --ro -a data2.qcow2 /media/foo /media/foo mountpoint is not empty fuse: mountpoint is not empty fuse: if you are sure this is safe, use the 'nonempty' mount option libguestfs: error: fuse_mount: /media/foo: Success I guess libguestfs uses the most recent 'errno' to report the error string, but it is zero (because the error was somewhere deeper, in fuse). regards, - assaf