I have a related Problem with a libvirt Guest running some Docker- Containers.
root@docker1:~# df -h Filesystem Size Used Avail Use% Mounted on /dev/sda1 7.9G 2.9G 4.6G 39% / udev 10M 0 10M 0% /dev tmpfs 794M 8.6M 785M 2% /run tmpfs 2.0G 672K 2.0G 1% /dev/shm tmpfs 5.0M 0 5.0M 0% /run/lock tmpfs 2.0G 0 2.0G 0% /sys/fs/cgroup none 7.9G 2.9G 4.6G 39% /var/lib/docker/aufs/mnt/8b510e9eb71523cf9afc723e11831a169c822b7251049f95ebed5e978b22184b shm 64M 0 64M 0% /var/lib/docker/containers/3d5542423739bc1a4467ce5e15a3b82224d2d1b315af75d7d91a0cc04e1e7b07/shm none 7.9G 2.9G 4.6G 39% /var/lib/docker/aufs/mnt/5d186a68a1fca2b58a440e6dbdf293853011a9526b819ac1dbcba7f91272535f shm 64M 0 64M 0% /var/lib/docker/containers/a4355f5e2a66b25a564c5027f818b4385cd417f85d8aaf79700ca4086fb86e63/shm none 7.9G 2.9G 4.6G 39% /var/lib/docker/aufs/mnt/e972052c347006cd8c79dc5bf9aaba07fdba2edeadc01e18e903d04ca4b05a86 none 7.9G 2.9G 4.6G 39% /var/lib/docker/aufs/mnt/e22995e962919ea50fcf7b4a5e52916e6839f76708d22e57e81de687af2f0dd0 shm 64M 0 64M 0% /var/lib/docker/containers/00e3490e37ded90e7421eb19e650cc684dec2b65a848a203c21212a549bf9e0e/shm shm 64M 0 64M 0% /var/lib/docker/containers/631b37644a0ac106b7d7403c2fcc3760d4647cb96141915b0aa7ae78f98e4e05/shm root@docker1:~# mount -l | grep /dev/vda2 root@docker1:~# mount -l | grep /dev/sda /dev/sda1 on / type ext4 (rw,relatime,discard,errors=remount-ro,data=ordered) /dev/sda1 on /var/lib/docker/aufs type ext4 (rw,relatime,discard,errors=remount-ro,data=ordered) I am not able to take snapshots: error: internal error: unable to execute QEMU agent command 'guest- fsfreeze-freeze': failed to freeze /: Device or resource busy Thank you Tim -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1587065 Title: btrfs qemu-ga - multiple mounts block fsfreeze Status in QEMU: New Bug description: Having two mounts of the same device makes fsfreeze through qemu-ga impossible. root@CmsrvMTA:/# mount -l | grep /dev/vda2 /dev/vda2 on / type btrfs (rw,relatime,space_cache,subvolid=257,subvol=/@) /dev/vda2 on /home type btrfs (rw,relatime,space_cache,subvolid=258,subvol=/@home) Having two mounts is rather common with btrfs, so the feature fsfreeze is unusable on these systems. Below more information about how we encountered this issue... Message send to qemu-disc...@nongnu.org: Message 1: ---------- I use external snapshots to backup my guests. I use the 'quiesce' option to flush and frees the guest file system with the qemu guest agent. With the exeption of one guest, this procedure works fine. On the 'unwilling' guest, I get this error message: "ERROR 2016-05-25 00:51:19 | T25-bakVMSCmsrvVH2 | fout: internal error: unable to execute QEMU agent command 'guest-fsfreeze-freeze': failed to freeze /: Device or resource busy" I don't think this is not some sort of time-out error, because activation of the fsfreeze and the error message happen immediately after each other: $ grep qemu-ga syslog.1 May 25 00:51:19 CmsrvMTA qemu-ga: info: guest-fsfreeze called This is the only entry of the qemu guest agent in syslog. $ sudo virsh version Compiled against library: libvirt 1.3.1 Using library: libvirt 1.3.1 Gebruikte API: QEMU 1.3.1 Draaiende hypervisor: QEMU 2.5.0 $ virsh qemu-agent-command CmsrvMTA '{"execute": "guest-info"}' {"return":{"version":"2.5.0", ... ,{"enabled":true,"name":"guest-fstrim","success-response":true},{"enabled":true,"name":"guest-fsfreeze-thaw","success-response":true},{"enabled":true,"name":"guest-fsfreeze-status","success-response":true},{"enabled":true,"name":"guest-fsfreeze-freeze-list","success-response":true},{"enabled":true,"name":"guest-fsfreeze-freeze","success-response":true}, ... } For making an external snapshot, I use this command: $ virsh snapshot-create-as --domain CmsrvMTA sn1 --disk-only --atomic --quiesce --no-metadata --diskspec vda,file=/srv/poolVMS/CmsrvMTA.sn1 Piece of reply 1: ----------------- I have encountered this before. Some operating systems may have bind-mounts that let a device appear multiple times in the mount list. Unfortunately the guest agent is not smart enough to consider a device that has been frozen as succesfull and keep going. This causes this specific error. Piece of reply 2: ----------------- Ok, that seems to be it. I’ve got the ‘/’ and ‘/home’ on the same device formatted as btrfs on two separate sub volumes. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1587065/+subscriptions