[Lustre-discuss] Lustre and Automount

[Bernd Schubert]

On Thursday 27 May 2010, Fraser McCrossan wrote:
> David Simas wrote:
> > On Thu, May 27, 2010 at 12:50:15PM -0600, Andreas Dilger wrote:
> >> There have been some reports of problems with automount and Lustre
> >> that have never been tracked down.  If someone with automount
> >> experience and config, and time to track this down could investigate
> >> I'm sure we could work it out.
> >
> > The autofs that comes with RHEL5 won't mount Lustre.  We got
> > it working with autofs-5.0.3-36, from some version of Fedora.
> > Later versions of autofs should also work.  The fix to autofs
> > is almost trivial.  A function scans the mount command to
> > make sure it contains just "legal" characters.  To get Lustre
> > to automount, it needs "@" in it's list of such.
> >
> > We did find that the automounter sometimes failed to remove
> > the Lustre record from /etc/mtab on unmounting the file system.
> > That would cause subsequent remounts to fail.  Another easy
> > fix: link /etc/mtab to /proc/mounts.
> 
> Also, remember that you can't mount Lustre subdirectories. That is, you
> can mount your Lustre filesystem as, say, /home, but you can't mount
> /home/username.

Without having checked the code, I think it should be fairly simple to add 
support for that in mount.lustre:

- Cut off the directory from the filesystem name

- Mount Lustre into a temporary directory

- Bind mount lustre into the target directory

The most difficult part will be to write a single entry into /etc/mtab


> 
> An approach that we are testing (but haven't tried in production yet)
> was suggested by an earlier post from Andreas Dilger, and involves two
> automounts. The first mounts the base Lustre filesystem(s) somewhere
> (say, /lustre) as a direct mount, the second is /etc/auto.home and looks
> like this:
> 
> *    -bind    :/lustre/&
> 
> In our case we have an executable map that generates the mount line
> based on the contents of the description field in LDAP (which indicates
> which Lustre FS contains the home - we have two), but the principle is
> the same.

That should work. The disadvantage of bind mounts is that 'lfs' does not 
recognize it as type lustre and therefore all those nice lfs subcommands will 
not work.


Cheers,
Bernd

--
Bernd Schubert
DataDirect Networks