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Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables"
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables" |
Date: |
Wed, 4 Feb 2015 09:31:32 +0000 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Tue, Feb 03, 2015 at 04:38:59PM -0500, Gabriel L. Somlo wrote:
> On Tue, Feb 03, 2015 at 02:11:12PM -0600, Michael Roth wrote:
> >
> > This does seem like useful functionality, but I think I'd like to know
> > more about the actual use-cases being looked at.
>
> The proposed functionality is mostly equivalent to that offered by
> "GuestInfo variables". So yes, initial activation scripts :)
>
> > Is this mostly about executing initial activation scripts? Because after
> > that point, a key-value store can be managed through the
> > guest-file-read/write interfaces for anything on the guest-side that's
> > interested in these variables.
> >
> > Even activation could be done using this approach, where the
> > scripts start QGA and wait for the host to coordinate the initial creation
> > of the file containing those variables, then setting a file marker that
> > allows activation to proceed. And if that seems wonky, I'm fairly sure you
> > could script the creation of the initial key-value store prior to starting
> > the guest using libguestfs:
> >
> > http://libguestfs.org/
>
> Specifically, I'm trying to port to QEMU a simulation/training setup
> where multiple VMs are started from the same base image, and guestinfo
> environment variables help each instance determine its "personality".
>
> Editing the disk image is not feasible, since the idea is to share the
> base disk image across multiple VMs. And needing to connect to each VM
> after having started it, wait for it to bring up the QGA, then get it
> to accept environment variables, that's precisely the wonkiness I'm
> trying to avoid :)
AFAICT, you're describing the exact scenario that cloud-init solves.
You have a generic cloud base image, and you provide metadata to the
guest (either via a transient CDROM image generated at boot, or via
a speciall network interface with well known IP addr + HTTP service)
which is uses to configure itself for a specific task as boot up.
Regards,
Daniel
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- Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables", (continued)
- Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables", Denis V. Lunev, 2015/02/03
- Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables", Eric Blake, 2015/02/03
- Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables", Michael Roth, 2015/02/03
- Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables", Gabriel L. Somlo, 2015/02/03
- Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables", Michael Roth, 2015/02/03
- Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables",
Daniel P. Berrange <=
- Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables", Gabriel L. Somlo, 2015/02/04
- Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables", Daniel P. Berrange, 2015/02/04
- Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables", Gabriel L. Somlo, 2015/02/04
- Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables", Daniel P. Berrange, 2015/02/04
Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables", Daniel P. Berrange, 2015/02/04
Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables", Christopher Covington, 2015/02/04
Re: [Qemu-devel] RFC: Proposal to add QEMU "Guest Environment Variables", Richard W.M. Jones, 2015/02/04