Hello,

the current version of the xen resource agent still uses the old fashioned
config file for the xen guest (domU). That file needs to be configured as
the xmfile option and is used when heartbeat starts the domU.

The problem with this file is that once the domU is created and started
that information is stored in the xen store. If you use any xen gui tool
like virt-manager to eg. attach another disk, that information is not
written to the old config file but it is written to the xen store. So it
can happen that you make changes to the running domU but do not update the
config file manually and when you migrate the domU you are wondering why it
does not work.

The xen command "xm list --long <domU>" exports the whole domU config from
the xen store (including the changes made by the gui) and writes them to
stdout in a xml near format called sxp. If you delete the domU from the xen
store, that output can be used to recreate the domU configuration.

So the current ocf resource agent uses the "xm create <domU config file>"
option to create and start the domU. The create option uses the old
fashioned formatted file, whereas "xm new -F <domU config file>" uses the
sxp formatted file and creates and starts he domU as well.

Would it be possible to extend the xen ocf resource agent to add another
parameter like "xmfiletype" which can be either "traditional" or "sxp" and
depending on, that the xen start command would be "xm create ..." or "xm
new ..." ?

This does not prevent that the administrator has to modify that xen domU
config file, but he can simply export the domU config and pipe it to that
text file, whereas the old fashioned file always needs manually changes.
There is no way to export it in that old fashioned way.

For backward compatibility that option could be set to "traditional" so no
old installations would break.

Would this be an option ?

If it would, I can enhance the ocf script and provide a patch for it.

Rainer


Allianz Elementar Versicherungs-Aktiengesellschaft
A-1130 Wien, Hietzinger Kai 101-105
FN 34004g, Handelsgericht Wien
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http://www.allianz.at

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