[Linux-cluster] rgmanager vm.sh using virsh under RHEL5.4

[Lon Hohberger]

On Mon, 2009-11-02 at 16:44 +0100, Alain RICHARD wrote:

> a) use_virsh = 1 per default
> b) that if your resource have a path attribute, vm.sh automatically
> revert to use_virsh=0, even if you hard code use_virsh=1 !
> c) there is no option to indicate the xml file that virsh use to
> create the vm. It always tries "virsh create name" where name is the
> vm name.

> The point a) is a little bit silly because if you have a RHEL 5.3
> cluster that is using xm configuration files, your vm will no longer
> launch after upgrade because it tries to do a "virsh create name"
> instead of "xm create name". It would have been probably cleaner to
> have "use_virsh = 0" per default to keep compatibility.

Libvirt's Xen mode loads config files from /etc/xen.  When you run
'virsh start foo' it will look for the config in /etc/xen which defines
the virtual machine named 'foo'.

So, effectively, either what you said above works for me or I don't
understand your problem.  Both 'xm' and 'virsh' modes work on Xen
domains in 5.4 (assuming you don't have a path attribute set):

  http://pastebin.ca/1653460

Did you mix 5.3 libvirt with 5.4 rgmanager or something?  If so, I'd
simply keep using the vm.sh from rgmanager in 5.3.

> The point b) will add compatibility to people that use the path
> attribute in order to store vm conf files in a place shared by all
> members of the cluster (gfs2 or nfs directory for example). It would
> have been clearer to document this feature because it is a little bit
> magical to see a resource with use_virsh=1 use in fact xm and not
> virsh !!!

You can't use "path" with virsh.  You are correct, though - it should
produce an error if someone explicitly sets use_virsh="1" with a path=
also set.  The two options can not be used together.

On making "virsh" mode more usable...

virsh supports 2 things:
  - Loading something by -name- from /etc/libvirt/qemu (or /etc/xen),
and
  - Defining transient virtual machines from a -file-

vm.sh when using virsh in 5.4 supports the former, but not the latter.
Federico Simoncelli wrote a patch to allow the latter for STABLE3:

http://git.fedorahosted.org/git/?p=cluster.git;a=commit;h=ea90559c936792e22576cac7a0bd0a2a50573426


> The point c) is very silly, because it restricts the configuration to
> be loaded from /etc/xen even for kvm !

Correct.  Well, /etc/libvirt/qemu for kvm, but... There's no way to
define alternate locations for VM config files in rgmanager from RHEL
5.4.


> Also their is no problem to use a "virsh create /path/to/file.xml"
> under RHEL 5.4 and I have found out that the cluster 3.0 stable branch
> have a new vm.sh file using an xmlpath attribute to solve this
> problem. Why this version was not back ported to RHEL 5.4 ? Is there
> any plan to do it ?

No, but it sounds like there should be.

-- Lon