Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables"

[Daniel P. Berrange]

On Wed, Feb 04, 2015 at 10:59:18AM -0500, Gabriel L. Somlo wrote:
> On Wed, Feb 04, 2015 at 03:24:32PM +0000, Daniel P. Berrange wrote:
> > Yes, there is some overhead in setting up QEMU on the host to provide
> > the data cloud-init needs, but it isn't all that difficult. For example
> > Rich Jones describes how to setup a virtual disk for cloud-init
> > 
> >   
> > https://rwmj.wordpress.com/2013/12/10/creating-a-cloud-init-config-disk-for-non-cloud-boots/
> > 
> > Given the prevalence of cloud-init across distros, I think you'll be hard
> > pressed to get them to support an alternative method, even if it is a bit
> > simpler at the QEMU setup level.
> 
> Have a look at this:
> 
> http://www.vmware.com/pdf/Scripting_API_23.pdf
> 
> (page 36, GuestInfo Variables).
> 
> It's a rather generic, flexible feature. Some people use it for
> early boot, but that's just one of the many use cases, so maybe
> focusing on "how to implement early boot configuration" is going
> a bit off on a tangent :)
> 
> I'd like to add that mechanism (or at least the host->guest bits)
> to qemu, for "feature parity". That should be a good thing, making
> it easier to port "whatever" to qemu, without having to massively
> rearchitect it to work around a missing feature...
> 
> Also, it's really non-intrusive. At this point, I could implement it
> by passing environment strings in via "-smbios file=./Type11EnvStrBlob",
> and read them on the guest side via 'dmidecode -t11', with some grep
> and awk magic thrown in for good measure :)

Perhaps cloud-init project would be interested in using the custom
smbios field as a data source for its needs. It already has the concept
of pluggable data sources, so adding another could be interesting.

Regards,
Daniel
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