Add info about mounting linprocfs under Linux Binary Compatibility

[Ross A. Beyer]

Hello,

I would first like to thank you for the FreeBSD Handbook, it really
is fabulous, and I rely on it all the time.

Recently, I was trying to get some legacy Linux programs running
on my FreeBSD 5.4-PRERELEASE system.  I could get some to work, but
not others.  A friend indicated that the programs that weren't
working required the /proc filesystem to get command line arguments.

After a fair amount of hunting around on the web, I found that by
doing a

	mount_linprocfs -o rw linprocfs /compat/linux/proc/

They worked like a charm.

I tried to find in the Handbook where I had missed this, and
could not.  The only documentation that I could find was in a
Security Advisory from December,
http://lists.freebsd.org/pipermail/freebsd-security-notifications/2004-December/000037.html, that said:

	In its default configuration, FreeBSD 5.x does not utilize
	procfs(5) or linprocfs(5) and will therefore be unaffected
	by this vulnerability unless the configuration is changed.


I'm writing to suggest that you add something about how FreeBSD 5.x
doesn't enable any proc filesystem stuff (procfs or linprocfs), and
that users may need to enable the Linux /proc filesystem from the 
command line as root via the above mount_linprocfs command, or 
show how it can be added to /etc/fstab.

I'd write a section for the Handbook myself, but I realize I don't
actually know the mysteries of the differences between procfs and
linprocfs to write something authoritative.  

I hope this helps improve the handbook.  Thanks again.
-- 
                                             Ross