[Triumf-linux-managers] autofs and ghosting

[Kel Raywood]

Greetings all:

I haven't received anything on this list since the subscription
announcement, so I thought that I'd send something to get things going.

As many of you know, the autofs (and autofs4) code in the Linux 2.4
kernel does not allow the option of "seeing" the mount points until they
are actually automounted. To see what I mean, login to ibm00 and do

cd /triumfcs
ls

Usually you will only see "linux" but a quick look in
"/etc/auto.triumfcs" shows that /triumfcs/alpha, /triumfs/home2,
/triumfcs/sciserv and /triumfcs/trshare are also available.  It would be
nice to see them in a directory listing even when they are not mounted.
This has been available in Solaris for several years (since 5.7 I
think); you specify the option "browse" in the automounter map.

You can play games with symbolic links by automounting somewhere else
(e.g. /automount/triumfcs/) and then putting symbolic links in /triumfcs
but it gets messy and doesn't work that well with some GUI
file-browsers.

However, there is no eqivalent functionality available for Linux.  Ian
Kent of Western Australia has made his "ghosting" patches available for
some time. They are now out of the beta stage and ready for public
consumption.  With the option "ghost" in your automount maps you get
the same functionality as the Solaris "browse" option. I have been using
it on PET-group machines for several months and had no problems.

The URL is: http://www.kernel.org/pub/linux/daemons/autofs/v4/

There is a source RPM for an updated autofs package and also the source
for un update autofs4 kernel module. You will not even need to reboot if
your autofs4 is built as a module as it is in all RedHat kernels.

I have only tried it on RedHat 9 installations but it works well on both
single-processor and SMP machines (including dual Xeon).  I have also
used it on RedHat 9 machines with the kernel from SGI that contains
patches for the XFS filesystem and it works fine with that.

Besides the ghosting option, the new autofs also adds other
functionality including direct mounts and automatic conversion of map
options to smbmnt arguments.

If anyone needs more help getting this going, then let me know.

Cheers,

Kel Raywood
TRIUMF/UBC PET Group