Startup item for Arla on MacOS X

[Samuel L. Bayer]

All -

I've succeeded in installing the prebuilt Arla 0.35.3 package for
MacOS X, and I've successfully dealt with Kerberos authentication. I
have a question about starting up Arla.

At boot time, the script in /System/Library/StartupItems/Arla is run,
which contains two commands:

/usr/arla/sbin/startarla
/usr/sbin/disktool -a xfs /afs 0

The effect of the second line seems to be to cache the entries in the
toplevel /afs directory, which takes quite a while at my site (I'm
behind a firewall and can't access any of them; I'm using Arla to
subscribe to AFS servers inside our firewall). 

I can't find any documentation on disktool anywhere on the Web, nor
have I been able to locate it in the Darwin source code. Running
"strings" on /usr/sbin/disktool provides some suggestive usage
information, such as that -a means an AFP mount, which adds the disk
to the Disk Arbitration internal tables. This is pretty much gibberish
to me. Can anyone point me to some documentation for disktool, or
explain why it is called in the Arla startup script, and whether it's
necessary?

Thanks in advance -
Sam Bayer
The MITRE Corporation
sam at mitre.org