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Re: [Xen-devel] Re-reading domain configs on domain restart

On Wed, 2012-02-08 at 16:32 +0000, Ian Campbell wrote:
> Hi Andy, 
> Good to meet you over the w.e.
> On Tue, 2012-02-07 at 17:30 +0000, Ian Jackson wrote:
> > Andy Smith writes ("[Xen-devel] Re-reading domain configs on domain 
> > restart"):
> > > I understand this will never be fixed in xend/xm, but would it be
> > > possible to have xl re-read the domU's config when the domU
> > > restarts?
> > 
> > Yes, this would certainly be possible.  Straightforward, even.
> > There are two questions we need to answer first:
> > 
> > Firstly, how should this be requested ?  I think a command-line option
> > to xl would do the trick.

> > Secondly, should we change the default behaviour ?  I'd be inclined
> > towards "yes" as the current arrangement is really rather perverse,
> > but I'm open to opinions.

Did we decide what to do here?

It occurred to me that rereading by default requires that the config
file still exist when the reboot happens, which may not be the case for
certain usecase which dump the config in a $TMPFILE or use the command
line syntax (someone said they did this). I suppose we could fallback to
the original config if the file no longer exists, but that would be
potentially confusing. Also I wonder if people do
        xl create template.cfg name="VM1"
        vi template.cfg
        hack it around
        xl create template.cfg name="VM2"
It would be odd for VM1 to turn into VM2 on reboot. Hrm, rereading also
takes no account of options passed on the command line on reboot.

As another (hopefully simple) idea how about a "xl dom-set-config" or
similar which (only) updates the config stashed in the userinfo to be
used on reboot? I would specifically exclude the possibility of this
reconfiguring the running domain for simplicity.


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