Re: Libvirt: dynamic ownership did not work

Jonatan Schlag <jonatan.schlag@xxxxxxxxxx> · Thu, 04 Aug 2016 20:28:36 +0200

Am Do, 4. Aug, 2016 um 5:07  schrieb Michal Privoznik <mprivozn@xxxxxxxxxx>:

On 04.08.2016 13:59, Jonatan Schlag wrote:

 Am Do, 4. Aug, 2016 um 1:38 schrieb Michal Privoznik <mprivozn@xxxxxxxxxx>:
 On 04.08.2016 12:12, Jonatan Schlag wrote:

  Am Do, 4. Aug, 2016 um 11:32 schrieb Michal Privoznik
  <mprivozn@xxxxxxxxxx>:
  On 03.08.2016 21:17, Jonatan Schlag wrote:
   Hi,
   I have a very strange problem with libvirt. I work on some machines
  with
   libvirt (Debian/ Arch Linux) and libvirt set the ownership of images
   file automatically to the qemu user / group for example on Arch
  Linux to
   nobody:kvm.
   So when I copy an image file with root and use I then with qemu,
  libvirt
   change the owner/ group to nobody:kvm.

   But I also compiled libvirt for a machine (gcc 4.9.4 glibc 2.12)
 and on
   this machine libvirt did not change the ownership of the image files
   which results in this error:

   libvirtError: internal error: process exited while connecting to
   monitor: able-ticketing,seamless-migration=on -device

 qxl-vga,id=video0,ram_size=67108864,vram_size=67108864,vram64_size_mb=0,vgamem_mb=16,bus=pci.0,addr=0x2

   -device intel-hda,id=sound0,bus=pci.0,addr=0x4 -device
   hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 -chardev
   spicevmc,id=charredir0,name=usbredir -device
   usb-redir,chardev=charredir0,id=redir0 -device
   virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x7 -msg timestamp=on
   2016-08-03T18:19:47.494512Z qemu-system-x86_64: -drive

 file=/data/hdd1/libvirt/images/test.img,format=raw,if=none,id=drive-virtio-disk0:

   Could not open '/data/hdd1/libvirt/images/test.img': Permission
 denied

  Can you please share the debug logs?

  http://wiki.libvirt.org/page/DebugLogs

  Also, my initial suspect, before diving any deeper is that usually,
 when
  users compile libvirt on their own, they forget to set the correct
  prefix, therefore libvirt is looking for its config files NOT under
  /etc/libvirt but /usr/local/etc/ or whatever.

  BTW: is the daemon running under root?

  Michal

  Hi,

  The daemon runs under root.

  I uploaded the debug logs to:

  http://people.ipfire.org/~jschlag/1363864/1_libvirtd.log

  The UID of the user nobody is 99, the GID of the group kvm is 1011.

  I added my configure options to the bug report.

  Following the log the ownership is changed but why is the file still
  owned by root:root?

 Right. the file is set ownership.
 But the file ist still owned by root:root and so it is not accessable by
 qemu as nobody:kvm. In the moment the only possible way is that the
 change of the ownership fail, but then there should be an error message,
 but there is no error message in the log.

Then the other option that comes to my mind is a race with somebody else
on the system. You can attach gdb to the daemon and set breakpoint to
virSecurityDACSetOwnershipInternal(). In the arguments you should see
the path eventually among with uid:gid.

BTW: what's the domain XML?

What did you need the xml file the domain is called test and the image file is /data/hdd1/libvirt/images/test.img

Michal

I did together with Michael Tremer some debugging and Michael posted our results in the bugtracker. So it seems that the chown function is not executed, because a other function return a wrong value.

Maybe the describtion in the bug report hepls to go furhter, when not say what you need (logs) to debug the problem.

Regards Jonatan

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