Re: shared NFS systems

[Kirk Strauser <kirk@strauser.com>]

Brian May <bam@debian.org> writes:

> Hello,
> 
> I think it should be an important goal of Debian to work
> properly, without resorting to hacks, on systems which share
> one or more files using something like NFS (from sharing /usr
> all the way through to sharing / for nfsroot systems).

We share /usr across roughly 10 workstations at the office
without problems.  We created a base installation with all of
the packages we thought we'd need, and with all of the hardware
drivers for the different boxen (i.e., various X servers).
Next, we grep'ed /var/lib/dpkg/info/* to see what packages
touched files outside of /usr - there were gratifyingly few.
Then, we created another base installation that was extremely
minimal, and then installed only the packages from the other
machine that had files outside of /usr.  Finally, we mirrored
the minimal drive to all of the client boxen, set up the "big"
installation on the server, and set every client to mount /usr
read-only from the server.

By auditing the list for extra-/usr packages, we isolated
everything that *had* to be installed locally.  The only
sub-optimal part was that each client had ~10MB of stuff in /usr
from the required packages, but that stuff got masked by the NFS
mount.

The only administrative trickery was coordinating the apt-get
updates across the boxen, which turned out to be pretty
trivial.  Procedure:

  - umount /usr on all clients
  - apt-get update every machine.  Remember, even the clients
    have a fully-working Debian install without the NFS mounts.
  - mount /usr
  - go back to work

Oh, and since we ran a Squid proxy on the server, we didn't have
11 systems downloading the same package from the FTP site.

How stable was this experiment?  We've been running it
continuously for close to a year without any significant (read:
took more than 15 minutes to fix) problems, and only 2 or 3
insignificant ones.  It did what it was supposed to, thankfully.

Oh, throw in NFS-mounted /home and NIS and you have a
generic-terminal system - any user can log in to any terminal in
any part of the office and go to work.  It works for us, at least.
-- 
Kirk Strauser