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Re: [fedora-virt] handling guest-service dependencies at boot time elegantly?



Bill McGonigle wrote:
> Hi, all,
> 
> Before I start hacking up my own poor solution, I'd like to run this by 
> the list and see if there's a good way to handle this.
> 
> I have a host (5.3 Xen Dom0) that has three guests:
> 
>   Fedora 10
>   Fedora 11
>   Nexenta 2
> 
> The Nexenta (opensolaris) guest's job is to provide storage services to 
> the Fedora DomU's, via iSCSI and NFS (ZFS storage).
> 
> My goal is to automate system startup.
> 
> My dependency tree looks like:
> 
>    Dom0 -> nexenta-DomU -> 'service iscsi'@Dom0 -> fedora-DomU's
> 
> Currently I have xendomains and iscsi set to 'chkconfig off' and the 
> fedora DomU's set for 'auto', and do:
> 
>   xm create nexenta
>   [watch xentop to see when it's running]
>   service iscsi start
>   service xendomains start

If I were going to do this, I'd write a very small daemon to run in the dom0
that just listens to a couple of ports.  On dom0 boot, I would start this
daemon, which would first exec "xm create nexenta", then wait around for a
little while listening from a connection on port, say, 4567.  Inside the nexenta
guest, you just have a simple "nc" command that connects to the dom0 once it is
booted, and acts like a "I'm ready" command.  Once your dom0 daemon receives
this, it can go onto the next step (service iscsi start), and then finally onto
your last step.

It's a bit hacky, but it centralizes control all in one place, and it is pretty
easy to write.

-- 
Chris Lalancette


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