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[libvirt-users] Stealing ownership: chown user->qemu->root



F12, libvirt 0.7.1-15, qemu 0.11.0-12, 32 bit

I recently discovered that libvirt is stealing ownership of my disk images. How can I make it stop?

I have a disk image in my home directory, owned by matt. When I create a domain that uses the disk it gets chowned to qemu.qemu. When the domain terminates it is owned by root.root. I've lost access to the file.

It has been suggested that the user->qemu happens to make sure that the qemu account can read/write the file. chmod'ing would be far better and avoid this problem. It appears that libvirt just assumes the disk image was owned by root before being chown'd to qemu.

Another problem with this is qcow disks. If chown'ing to qemu is to ensure that qemu has access to all the disks needed for the domain, it fails for qcow, because the base disk is not chown'd as well. This can result in a very cryptic error message (funny period (.)):

  monitor socket did not show up.: No such file or directory

For instance, base.img is owned by matt (u=rw,go=), a qcow disk qcow.img is linked to base.img. When a domain using qcow.img is created qcow.img is owned to qemu, but base.img is not.

Instead of chown'ing, will libvirt provide an error that could cover both these situations? The virt-manager GUI (or virsh TUI) could interpret that error and chmod the proper files transparently, or preemptively chmod the required files. Users of the libvirt API would have to make sure things are setup properly at first and would not have to worry about side-effect changes made by libvirtd.

I think the suggestion holds even if is only the qemu driver doing the chown.

Best,


matt


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