Re: [Xen-users] how to start VMs in a particular order

[Simon Hobson <linux@xxxxxxxxxxxxxxxx>]

lee <lee@xxxxxxxxxxxxxxx> wrote:

>> I solved that part of the problem by running a local nameserver on
>> every "key" system (not all of them VMs), with local slave copies of
>> the zones we use, and using our main resolver as a forwarder for
>> everything else. That at least means the routers and firewalls can
>> start up independently when the power comes back on.
> 
> Running a slave name server on dom0 might solve this problem for me.
> But I don't really want to do that --- going that way, I could run
> everything on dom0.

I don't run it on Dom0, but on each system where it's needed. Some of these are 
standalone boxes (eg routers), some are VMs, but I've just tried to make them 
all so they can cold start independently of other systems. So if we have a "big 
red switch" moment, at least we'll get the core systems running normally and 
only have to intervene on a few.

>> The server room is lovely and quiet when the power's gone off !
> 
> Manufacturers need to make hardware that doesn't need so much energy ...


Like none :)


> That's the problem:  How do you try to resolve a hostname, and how do
> you find out whether a NFS server is up or not?

For a hostname, you can do something like "host <some FQDN> <IP address of the 
DNS server you're dependent on>". If you get a timeout then the service isn't 
up yet, if you get the right answer then it is.
For something like NFS, you could check to see if a mount is mounted, and if 
not pause and try again to mount it.


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