determining the real directory when using automounts

[Brent Callaghan]

The symbolic links for the 4.0.1 automounter were made more attractive by
attempting to recreate the original path, with the exception of "/tmp_mnt"
stuck on the front.  The 4.0 version used to invent disgusting pathnames
via tmpnam(3).

The symbolic links look pretty good for most mounts - except if you use
the subdirectory feature in a map (i.e. a second colon).  This feature
allows the automounter to do the mount at a higher level and thus allow
several map entries to share a common mount.  One side effect of this
shared mount point is that it's now impossible to build a completely
satisfying symbolic link.  The 4.0.1 automounter fudges a path by
incorporating the key used in the first reference that caused the mount.
This is best illustrated with an example:

An automounter map to mount user's home directories.  The map is looked up
by loginname - not servername.

	brent      sparky:/home/sparky:brent
	derek      sparky:/home/sparky:derek
	cindy      sparky:/home/sparky:cindy
	fred       gurgle:/home/gurgle:fred

I mount this map on /home thus:

	automount /home /etc/auto.home

Then I do the following:

	$ ls -l /home/brent
	lrwxrwxrwx  /home/brent -> /tmp_mnt/home/brent/brent
	$ ls -l /home/derek
	lrwxrwxrwx  /home/derek -> /tmp_mnt/home/brent/derek
	$ ls -l /home/cindy
	lrwxrwxrwx  /home/cindy -> /tmp_mnt/home/brent/cindy
	$ ls -l /home/fred
	lrwxrwxrwx  /home/fred -> /tmp_mnt/home/fred/fred

The symbolic links are all pointing to the right places, it's just that
the names look a little weird.  If you use this scheme for mounting your
home directory you can "fix up" the name by having the shell keep track
for you.  Both the C shell an Korn shell keep the original path in $PWD.
You can set up an alias so a "pwd" will echo $PWD.  If you still don't
like the idea of weird symbolic links, then just replace second colon in
the map entry with a slash and put up with the overhead of extra mounting.
The pathname will still be longer than you expect, but not quite so weird
and unpredictable.

	Brent