Le jeu. 14 nov. 2024 à 17:00, Frantisek Rysanek <frantisek.rysa...@post.cz> a écrit :
> > 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 > > my problem is exactly this, the link between `device`, `drive` and `blockdev` : while `device` and `drive` link quite easily, I can't link `blockdev` to the other two... setting aside the fact that the image is used elsewhere, my aim is to mimic `-hda file.qcow2` but without taking the lock into account (`locking=off`). I currently do this: ``` # qemu-nbd -c /dev/nbd0 file.qcow2 # mount /dev/nbd0p1 /mnt -o uid=me $ # do some changes in /mnt/... # umount /mnt # qemu-nbd -d /dev/nbd0 $ qemu-system-x86_64 -snapshot -hda file.qcow2 # qemu-nbd -c /dev/nbd0 file.qcow2 # mount /dev/nbd0p1 /mnt -o uid=me $ # do some changes in /mnt/... # umount /mnt # qemu-nbd -d /dev/nbd0 $ qemu-system-x86_64 -snapshot -hda file.qcow2 # qemu-nbd -c /dev/nbd0 file.qcow2 # mount /dev/nbd0p1 /mnt -o uid=me $ # do some changes in /mnt/... etc... ``` and I'd like to be able to do this : ``` # qemu-nbd -c /dev/nbd0 file.qcow2 # mount /dev/nbd0p1 /mnt -o uid=me $ # do some changes in /mnt/... $ qemu-system-x86_64 -snapshot -hda file.qcow2 # with locking=off $ # do some changes in /mnt/... $ qemu-system-x86_64 -snapshot -hda file.qcow2 # with locking=off $ # do some changes in /mnt/... etc... ```
