[9fans] Permissions, again

[Lucio De Re <lucio@proxima.alt.za>]

I'm obviously too off-tune to understand Plan 9's permission scheme,
it keeps catching me out.  I suppose the lack of "root" to solve
all problems does require a clearer understanding and I'm notoriously
slow.

I haven't yet installed 4ed but I've been having a good look at
the distribution and especially the man pages.  There's a lot of
exciting stuff in there.

In my exuberance, I thought I'd install the ISO image as a file
and access it using 9660srv(1) which is a very handy way indeed to
read the various documents etc.

Where I failed, was when I thought I'd alter something (I forget
what) on the image.  Now, I have no idea how complicated it is to
manage an ISO image (specially one with multiplicates :-) but it
would have been so nice to be able to do it that I really regretted
receiving a "permission denied" or somesuch.

Naturally, I did attempt to tidy up all the permissions (I see Rob
owns more or less all the image contents) as well as the underlying
ones (I was using disk/kfs at the time) but that was quite
unsuccessful.

I presume that the ISO image was generated in some fashion and I
haven't yet found out how, so please illuminate me, but mostly I'd
be very excited to discover that 9660srv can modify an ISO image
and retain its structure successfully, if it needs some work and
someone wants to guide me, I'll happily help.  I did note that the
4ed version has some undeployed code for "removing" files where
the 3ed version has just the "not supported" message.

Back to permissions, it may be just something in the way I set
things up that blocked my use of 9660srv, so a short lesson on
layered permissions would be welcome:

	% cd /dist/Plan9/4ed
	% bunzip2 < plan9.iso.bz2 > plan9.iso
	% 9660srv
	% mount -c /srv/9660srv /n/kremvax plan9.iso
	% cd /n/kremvax/sys/src/cmd

this is from memory.  What would it take to allow me to edit a file
or create a directory at this point?

++L