Re: [gentoo-cluster] Gentoo clustering à la www. clustermatic.org (PXE booted nodes)

[Jordan Dawe]

In any case, we're getting Off Topic, I wanna make this a Gentoo Kluster (C) 
(one may inster Kick Ass somewhere in there :P ). Moreover, I am _mandated_ 
to do this as part of my masters _and_ document this Document which I 
will of course make available to the Gentoo community. I'm almost thinking of 
looking onto either an ebuild or even a special profile for making the 
node's ROOT image (with a modified baselayout)


So, as always, if anyone can help out in either pointing to documents or 
sharing experience, I would be more than glad to put this together and really 
put Gentoo on the HPC map.
 

I tried to bang together something like this while I was building a 
cluster for our department.  It's real tricky though, especially if you 
don't want to mount root over NFS--and mounting root over NFS always 
seems like a huge amount of overhead to me.  I was able to get a second 
box booting off tftp and mounting filesystems across nfs, but I didn't 
have any idea how to set about making a boot image and transmitting that 
to a ramdisk to boot off of.


Have you checked out warewulf?  It's quite good; a complete ramdisk 
based cluster setup package.  I switched to it after failing with 
gentoo.  If I was going to approach this project, I would rip warewulf 
apart and see how they do what they do.  Warewulf is RPM based, but it 
should be easy to convert a lot of the RPM steps in warewulf to 
ebuilds.  Then you could make an ebuild to generate the ramdisk image, 
like warewulf does.  In any case, Warewulf has solved a lot of these 
problems in a different context; check it out.


http://www.warewulf-cluster.org/cgi-bin/trac.cgi

It also has tools to manage a cluster, observe processess on the nodes, 
etc.  I'm really, really happy with it, except for the not working with 
gentoo part of it.


Jordan

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Re: [gentoo-cluster] Gentoo clustering à la www. clustermatic.org (PXE booted nodes)

[Donnie Berkholz]

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Mathias Weigt wrote:
| Donnie Berkholz wrote:
| What exactly do you want more detail about?
|
|
| They boot to an initrd containing busybox, then proceed to mount
| necessary bits from a read-only NFS export and other bits via tmpfs
| where they need to write, then pivot_root into the new NFS root.
|
| I'd like like some instructions how to do these things you wrote above.
| If you don't like to write a huge essay, I don't mind getting  it step
| by step.

A linuxrc file does all sorts of stuff. linuxrc is a file within an
initrd that gets automatically executed when booting into the initrd.
The initial, skeletal linuxrc downloads a more complex script called
linuxrc.real from the NFS server and executes that.

The more complex script mounts a number of NFS exports (/ and so on),
then mounts tmpfs for the areas that need write permissions (chunks of
/var and so forth). Another option here would be a unionfs, but I
haven't looked into it.

Originally, I got both of them from xmerlin (another dev), and modified
them a bit to fit my circumstances. I'll look around a bit to see
whether I can find them, and send them along.

Another thing you'll want to look into at this point is using initramfs
instead of initrd. initramfs is initrd's successor and operates a bit
differently.

Thanks,
Donnie
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