Re: news from the Debian Beowulf project?

[Fabrice Lorrain <Fabrice.Lorrain@free.fr>]

Adam C Powell IV a écrit :
> On Fri, 2007-04-20 at 00:41 +0200, Fabrice Lorrain wrote:
> > Adam C Powell IV a écrit :
> > > Greetings,
> > >
> > > On Sun, 2007-04-15 at 09:35 +0200, karel lang wrote:
> > > > hello,
> > > > i'd like to ask, if there are some howto's or materials like that of 
> > > > newer date about installing and maintaining the Beowulf project on 
> > > > Debian Linux.
> > > As far as I know, the most current Debian-specific howtos are on the
> > > Debian Wiki: start at http://wiki.debian.org/?DebianBeowulf .  There are
> > > many Debian-specific enhancements such as update-cluster, FAI, dsh, etc.
> > > which make facilitate cluster management on Debian.  There is of course
> > > still room for improvement, e.g. generating dhcp server config files
> > > using update-cluster (bug 156810); ideas and patches are always welcome.
> > >
> > > Unfortunately, since the Beowulf Wiki pages were written (mostly by
> > > yours truly), the diskless package has been orphaned, so that section is
> > > valid through sarge but not for etch.  Would someone be interested in
> > > redoing that section for lessdisks -- or in re-introducing diskless?
> > > (Though the latter will not help with etch.)
> > Hello,
> >
> > I would suggest to have a look at Daniel Baumann & all work on 
> > debian-live [1] before (re)starting any work on {less}disks{less} packages.
> >
> > The infrastructure (debian-live + etch initrd + unionfs) provided to 
> > build live cd makes it trivial to build diskless environnements. See the 
> > wiki for the technical informations.
> >
> > As debian-live is here to stay, regrouping human effort there seems more 
> >    effective than splitting it over several overlapping package.
>
> Excellent point Fabrice.  It seems there's also an LTSP howto on the
> Wiki.  I've marked DiskLess as deprecated.
>
> On the other hand, diskless (and I presume lessdisks and LTSP, though
> I'm still using sarge diskless packages on etch) has a lot of very nice
> features for minimizing the hard drive space of a cluster (by not
> repeating /usr, /bin, /sbin, /var/lib/dpkg etc. over the various client
> images), nice maintenance tools, etc.  For example, chroot into one
> place, apt-get update dist-upgrade install remove etc. to update the
> main chroot, then exit the chroot, and run a simple script which updates
> all of the images' /etc and /var directories (outside of /var/lib/dpkg).

<disclamer: I'm not a user of the cited packages, but I've a descent 
understanding of how they work/>

I agree with you that minimizing disk storage is important. Chroot + 
aptitude {update,upgrade} (apt-get should die). is a must have
( = simplicity of maintenance).

Debian-live is using unionfs [1] which allow to mount-merge a ro branch 
with a rw one. Concretly, it meens you export your 
/srv/etch-root_chrooted to your cluster nodes and in the initrd you 
merge it with a rw tmpfs where you can put the few files you need to modify.

In short, you have a single image for all your client. You can maintaine 
it with the chroot/aptitude upgrade trick.

> Debian Live seems geared toward providing an image for a single client
> machine for a static image, so I don't know if that's what Beowulf
> people really want.  Is it possible to update?  How can one copy over
> multiple images, while preserving their separate configurations?

My personnal experience, but for workstations (not a cluster 
environnement) is that there is very few files to manage 
hardware/environnement differences.

If you really need to keep separate configuration for each node, you can 
  maintain them on the server-side (ip or hostname directory tree) and 
merge them in the tmpfs/unionfs on the client during the initrd 
initialisation.

FYI, LTSP, knoppix and quite a lot of other livecd-distrib have been 
using unionfs or it's half-fork AUFS for more than a year know.

@+,
	Fab

[1] http://en.wikipedia.org/wiki/UnionFS
[2] http://aufs.sourceforge.net/