> my image `fie.qcow2` is mounted elsewhere (nbd) and running > `qemu-system-x86_64 -snapshot -hda file.qcow2` fails with the error > "qemu-system-x86_64: -hda usb1.disk: Failed to get shared “write” > lock / Is another process using the image [usb1.disk] ?".
Oh... So you want concurrent access to the block device. 1) have it mounted on the host=HV using qemu-nbd 2) while at the same time, you want to give it to a guest VM? Unless you use a filesystem such as GFS2 or OCFS2 inside the partitions that exist inside that QCOW2 black box, or mount it read-only at both ends, you are asking for trouble :-) That is, if QEMU permits unlocked access by a VM, parallel to the qemu-nbd loop-mount. Note that this is just a tangential pointer on my part. Just a start of a further journey. Further reading and study. If you really want concurrent access to a directory tree, consider using something like Samba or NFS as the simpler options. Then again, concurrent access is definitely fun to play with and grow :-) Frank
