Xen users - May 2009 - A few questions about creating/restoring VM''s...

Hey guys,

I have 3 Xen VM''s running in production and am overall very pleased, 2
things that have stumped me that I was hoping some Xen pros might be  
able to enlighten me about are is the following:

1) Most of the documentation I read says that my Xen config files  
should be name like "domain.sxp" but all of my configs are in a  
randomly generated (id looking) folder in /var/lib/xend/domains, as an  
example: e7850ca2-aaf1-5c92-f62d-cb29e5859d33. Is that ok?

2) I have been looking for the best way to create an easy to restore  
copy and seem to have figured most of this out. My question is, if I  
have a backup of the config, is it possible to use xen-create-image  
and build a new VM from scratch with the exact same config? I''d like  
to simply be able to (in the even of a system failure) grab a copy of  
the VM and rebuild the Xen VM''s. I have Google''s aplenty but
no one
seems to be unanimous on the best way to do this.


Thanks guys!

--
Travis Bell









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On Sat, May 9, 2009 at 10:49 AM, Travis Bell <travisbell@me.com>
wrote:
> 1) Most of the documentation I read says that my Xen config files should be
> name like "domain.sxp"
It can be any name you want. It doesn''t even have to be *.sxp.
> but all of my configs are in a randomly generated (id
> looking) folder in /var/lib/xend/domains, as an
> example: e7850ca2-aaf1-5c92-f62d-cb29e5859d33. Is that ok?
domU config files used to be files under /etc/xen. If you want it to
autostart, you could create a symlink under /etc/xen/auto. This is
still the case with RHEL5.

Newer versions of Xen uses sxp config files (although the old format
is also still usable). You could also have xend manage the config
file. This is the default when using virt-manager/virt-install (or
similar) on newer versions of Xen (including the one on Opensolaris).
This is what you have.

You can "convert" old files to xend-managed config using "xm
new". The
reverse process can be done by copying the config file (the one you on
/var/lib/xend/domains/*/config.sxp) and running "xm delete"
afterwards.
> 2) I have been looking for the best way to create an easy to restore copy
> and seem to have figured most of this out. My question is, if I have a
> backup of the config, is it possible to use xen-create-image and build a
new
> VM from scratch with the exact same config?
Not sure about xen-create-image, but the general answer is yes.
> I''d like to simply be able to
> (in the even of a system failure) grab a copy of the VM and rebuild the Xen
> VM''s. I have Google''s aplenty but no one seems to be
unanimous on the best
> way to do this.
a Xen domU generally consists of :
- domU storage, which can be a file or block device (PVM, partition, etc.)
- domU config file (like the one on /var/lib/xend/domains)
- kernel and initrd, if it''s located on dom0. This is not necessary
for HVM domU or PV domUs with pygrub, as the kernel will be inside
domU''s storage.

Get those and you can easily clone domU.

Regards,

Fajar

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