Nico,
Is there a smarter xendomains script out there that deals with domU
dependencies better than the one in the RPMs (CentOS)?
For example, directory services (eg. LDAP, DNS) are on one domU, and
other domUs depend on those services to boot correctly. (Best to
solve this with redundant services, yes, but let's say this is a test
network.) An even stranger example is a domU whose root boots from
an NFS, iSCSI or AoE filesystem on another domU.
That's not a Xen issue: that's an OS issue. As such, the init scripts
of the other DomU's could perform a number of checks to see if the
services are enabled yet [...]
Yes, you're right, and I didn't explain my idea clearly.
When I wrote 'smarter', I really meant something like the following: an
administrator knows that the directory server must be booted first and
others later. In a config file somewhere referenced by the xendomains
init script, probably the same one below that configures per-domU
settings for shutdown, he inserts the option to, for example, boot the
dir. server immediately, and then wait 30 seconds to boot the remaining
servers. This is a simple example, and there are probably use cases
where more expression of more complex dependencies would be desirable.
It would also be nice, for example, to have per-domU settings for
shutdown (hibernate or init 0?).
This idea is still in a seed stage, so I'm not expressing it very
clearly. Any pointers to similar-sounding information, though, are
well appreciated. Thanks-
Well, there you'd have to get into the "xendomain" init script that
RedHat uses. It's an interesting idea: the information could
theoretically be contained in a standard Xen init script, and even
reported to the Xen configurations for migration. But in the short
term, a sinple text-file with domain names and shutdown states could
be stuffed in /etc/sysconfig/ or /etx/xen/ for exactly this sort of use.
So yes, the xendomains init script is where this work would have to be
done. The RH xendomains script, and the one shipped with the
xensource-provided RPMs, are the same IIRC, and both simply fire up all
configs that exist in /etc/xen/auto (smart enough, at least, to wait a
few seconds between successive fire-upings).
For now, I am also tempted to stick things into an /etc/sysconfig file
or perhaps to set variables in the /etc/xen/config scripts. This is
just a hack for now, though, and there is probably a smarter way to
integrate this information into the Xen system somewhere.
John
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