On Thu, 2020-08-06 at 15:45 +0200, Marc Hartmayer wrote:
On Tue, Aug 04, 2020 at 11:39 PM +0200, Andrea Bolognani <abologna@redhat.com> wrote:
This patch broke libvirt in Debian for certain setups.
With AppArmor enabled (the default), the error is
$ virsh start cirros error: Failed to start domain cirros error: internal error: Process exited prior to exec: libvirt: error : Cannot delete directory '/run/libvirt/qemu/1-cirros.dev': Device or resource busy
If I disable AppArmor by passing security='' on the kernel command line, the error message changes to
$ virsh start cirros error: Failed to start domain cirros error: internal error: Process exited prior to exec: libvirt: QEMU Driver error : Unable to get devmapper targets for /var/lib/libvirt/images/cirros.qcow2: Success
An effective workaround is to set namespaces=[] in qemu.conf, but that's of course not something that we want users doing :)
The underlying issue seems to be caused by the fact that, on a Debian installation that uses plain partitions instead of LVM, /proc/devices doesn't contain an entry for device-mapper right after boot, which... ... this code expects.
Running
$ sudo dmsetup info No devices found
We see the same problem as mentioned by Andrea. The host kernel configuration used:
… CONFIG_BLK_DEV_DM_BUILTIN=y CONFIG_BLK_DEV_DM=m …
As soon as we load the kernel module ‘dm-mod‘ everything works because then ‘device-mapper‘ is listed in /proc/devices.
Thanks Marc! I have confirmed that Debian also uses the same kernel configuration as the one you have reported above, and that running dmsetup(8) causes the dm-mod kernel module to be loaded. For comparison Fedora, where everything works fine, uses CONFIG_BLK_DEV_DM_BUILTIN=y CONFIG_BLK_DEV_DM=y -- Andrea Bolognani / Red Hat / Virtualization