[libvirt-users] Libvirt: dynamic ownership did not work

[Laine Stump]

On 08/04/2016 07:59 AM, Jonatan Schlag wrote:
>
>
> Am Do, 4. Aug, 2016 um 1:38 schrieb Michal Privoznik 
> <mprivozn at redhat.com>:
>> On 04.08.2016 12:12, Jonatan Schlag wrote:
>>
>>     Am Do, 4. Aug, 2016 um 11:32 schrieb Michal Privoznik
>>     <mprivozn at redhat.com <mailto:mprivozn at redhat.com>>:
>>
>>         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
>>     <http://people.ipfire.org/%7Ejschlag/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.

Are you checking it after the operation has failed and libvirt has 
continued? If libvirt fails to access the file, it will then set 
everything back to its original state, so looking at the file ownership 
after the fact tells you nothing. If you really want to see if the file 
has the proper ownership, you need to attach gdb to libvirtd and set an 
appropriate breakpoint.

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