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

["J. Roeleveld" <joost@xxxxxxxxxxxx>]

On Saturday, June 28, 2014 08:25:11 AM lee wrote:
> "J. Roeleveld" <joost@xxxxxxxxxxxx> writes:
> > On Thursday, June 26, 2014 06:19:30 PM lee wrote:
> >> Since dom0 crashes once every 24 hours, it would be nice if I could at
> >> least get the machine rebooted without more intervention than having to
> >> press the reset button ...
> > 
> > I would fix this with a higher priority, to be honest.
> 
> Yes, if I could ...
> 
> So far, I might have made some progress on that by removing a package
> that checks the status of the RAID volumes.  It's too early to tell for
> sure; at least the server hasn't crashed since.

Interesting. Maybe check on a Debian mailing list to see what that package 
might be doing to cause a crash?

> On Debian, /etc/init.d/xendomains seems to be what brings up the domains
> automatically.  It would be a good place to add a timer or to add checks
> for services.

That script is part of Xen, not just Debian. I have the same file in Gentoo.

> As to numbering file names/links:
> 
> lee@heimdall:~$ mkdir ordertest
> lee@heimdall:~$ touch ordertest/3
> lee@heimdall:~$ touch ordertest/2
> lee@heimdall:~$ touch ordertest/0
> lee@heimdall:~$ for name in ordertest/*; do echo $name; done
> ordertest/0
> ordertest/2
> ordertest/3
> lee@heimdall:~$ touch ordertest/100
> lee@heimdall:~$ for name in ordertest/*; do echo $name; done
> ordertest/0
> ordertest/100
> ordertest/2
> ordertest/3
> lee@heimdall:~$
> 
> 
> So when you're careful, you can specify the order in which VMs are
> brought up (at least when using Debians' script) --- but is it a granted
> feature that the names always appear in any particular order?  It looks
> more like a side effect.

It is how the shell, by default, orders files when enumerating wild-cards.
This can be relied upon.

> Anyway, I think I'll modify the script so that the domains are brought
> up in a particular order with fixed delays as needed.  That seems the
> most simple and efficient way to do it.

I did something similar.
I have the following directories:

****
# ls /etc/xen/auto/
disabled  stage1  stage2  stage3  stage4  stage5
****

I then have duplicates for the xendomains script, with a few changes, that 
starts the domains in the relevant stage folder.
Currently, I check that the domains in the stage-folder are started 
successfully before the next one is started.

Thanks to a stable server and reliable UPS, I do not have a pressing need to 
automate this process urgently, but to make the server easier to manage, I do 
need to build a reliable method.
Currently, I am more interested in adding a method for cross-system 
dependencies.

--
Joost

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