[Fedora-livecd-list] Live ISO within initrd for PXE Boot?

[Daniel P. Berrange]

On Sun, Feb 17, 2008 at 10:33:40PM -0500, Warren Togami wrote:
> Chris Lalancette wrote:
> >Warren Togami wrote:
> >>http://git.fedoraproject.org/git/?p=livecd;a=commit;h=e0f0269d3a8f8f310e7c5fdfb8af45892f419c13
> >>>The way it works is to bundle the complete ISO image inside the initrd.
> >>>The kernel and (bloated) initrd are downloaded using PXE in the normal
> >>>way, and the init script finds and loopback-mounts the ISO image and
> >>>booting continues as normal.
> >>Wow.  I don't mean to offend, but this seems like an incredibly bad way 
> >>of doing this.  Isn't this really slow in the boot up because you must 
> >>wait for the entire ISO to download?  It also requires the client to 
> >>have more than enough RAM to have the entire ISO in memory?  It sounds 
> >>like the entire memory used by the ISO remains unavailable to the booted 
> >>system.
> >
> >Well, it depends on your definition of "bad".  For the purposes I
> >originally wrote it for, the ISO is going to be fairly small (~70MB or
> >less), and the target machines will have a lot of memory.  So for that
> >situation, it works well enough, doesn't waste an appreciable amount of
> >memory, and fits into existing tools fairly easily.
> 
> Ah, I didn't realize that you were using livecd-tools and mayflower for 
> a rescue or install type image.  ~70MB really isn't so bad, and you are 
> right about one less service to configure being a benefit.

It is not technically a rescue or an install image. The so called 'managed
nodes' simply run guest VMs & are effectively stateless. You just boot up
the minimal image containing only the libvirt daemon and enough utils to
bring up networking and login to iSCSI targets. Once up it connects to the
admin node and waits to be told to run guest VMs. All the VM's storage and
any persistent config is off on iSCSI or in the admin node. With such a
specific application use case & controlled environment is the  perfect 
stateless host scenario. The admin will never even login to a managed node,
if it breaks just deploy a new node - each node is totally disposable at
any time (well bar a little VM downtime, or pre-emptive migration).

Dan.
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