4.2 Info request: Read-only file systems

[Landon C. Noll]

I would like to mount things like /bin, most of /etc, /usr/{bin,lib, ... },
/dev/{mem,kmem,...}, usw...  on a read-only disc pack.

What is needed (if it can be done) to be done to unix to allow this?

A guess is that one needs to change the mountfs call in init_main.c to
pass a read-only flag.  One would need to add an additional mountfs
call to mount a second writable pack.  Files which need to be written
such as /etc/utmp, or /usr/adm would be symbolicly linked over to
the write pack.  What problems are connected with that?

What about the /dev/ttyxx files.  To allow getty/login to play with the
ownership, one might need to symbolic link to the write pack as well.
Will this cause a problem?

Does unix assume that it can write on root?  (my guess again is that one
the superblock timestamp update for root is not needed since I can get
the starttime for a real time clock)  What about last file access times? 

chongo <thanx> /\../\
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