[virt-tools-list] virt-manager destroys symlinks to guest configs

[Eric Blake]

On 02/20/2012 09:58 AM, Cole Robinson wrote:
> On 02/20/2012 11:21 AM, Jakub Mroziński wrote:
>> Hi,
>> virt-manager after saving guest config destroy symlink to this file and
>> creates new file. How to reproduce:
>>
>> cd /etc/libvirt/qemu
>> # mv openbsd.xml /mount/
>> # ln -s /mount/openbsd.xml 
>> # ls -l openbsd.xml 
>> lrwxrwxrwx 1 root root 49 Feb 20 17:09 openbsd.xml -> /mount/openbsd.xml
>> # virt-manager

Unsupported.  /etc/libvirt must be a local directory on each host, and
_must not be shared_ between machines.  There are a few subdirectories
under /etc/libvirt and /var/lib/libvirt that can be shared (in fact,
http://libvirt.org/locking.html documents that /var/lib/libvirt/sanlock
must be shared to be useful), but these are the exception, not the rule.

>>
>> Now we need to edit host openbsd in virt-manager then "Apply" changes and we got:
>> # ls -l openbsd.xml
>> -rw------- 1 root root 2076 Feb 20 17:13 openbsd.xml

Correct - libvirt will not follow symlinks when saving internal
configuration, but rewrites the file from scratch without preserving the
symlink.  And I don't think this is a bug, since we already explicitly
document that files under /etc/libvirt are internal to libvirt, and must
not be shared.  Rather, it is probably an intentional side-effect of a
recent libvirt change to atomically update internal .xml files (libvirt
used to write over internal files in a non-atomic manner, which could
corrupt domains if a power outage occurred at the wrong moment).

>>
>> I have network storage and move every configuration there. On host i want have
>> only symlinks. I know that i can do workaround, but i dont want.

If you want to store your configuration in shared storage, then the only
supported method of doing that is to store the XML independently of
/etc/libvirt.  For example, you can 'virsh dumpxml $dom >
/mount/$dom.xml' to save off the configuration to shared storage, and
'virsh define /mount/$dom.xml' to reload the shared configuration if you
don't trust what might be in place locally.

-- 
Eric Blake   eblake at redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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