'Failed to get "write" lock' error when trying to run a VM with disk image file on an SMB share

[Adam Williamson]

This has been reported and discussed downstream:

https://bugzilla.redhat.com/show_bug.cgi?id=1484130

but doesn't seem to be getting a lot of traction there.

Basically, with qemu since at least 2.10, you cannot use a disk image on an SMB share that's mounted with protocol version 3 (I think possibly 2 or higher). This is made much more serious because kernel 4.13 upstream made version 3 the *default* for SMB mounts, because version 1 is insecure and should not be used.

So basically, anyone with a recent qemu and kernel cannot use disk images stored on an SMB share. This is a major inconvenience for me because, well, an SMB share is exactly where I store my VM disk images, usually: I have a big NAS drive where I keep them all, only now I can't because of this bug, and I'm manually swapping them in and out of the very limited space I have on my system drive (SSD).

The error you get is:

qemu-system-x86_64: -drive file=/share/data/isos/vms/desktop_test_1.qcow2,format=qcow2,if=none,id=drive-virtio-disk0: Failed to get "write" lock
Is another process using the image?

[Thomas Huth (th-huth)]

The QEMU project is currently considering to move its bug tracking to another system. For this we need to know which bugs are still valid and which could be closed already. Thus we are setting older bugs to "Incomplete" now.
If you still think this bug report here is valid, then please switch the state back to "New" within the next 60 days, otherwise this report will be marked as "Expired". Or mark it as "Fix Released" if the problem has been solved with a newer version of QEMU already. Thank you and sorry for the inconvenience.

[Launchpad Janitor (janitor)]

[Expired for QEMU because there has been no activity for 60 days.]