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Re: r/o root filesystem?



In article <878yvt6o0n.fsf@stark.dyndns.tv>,
Greg Stark  <gsstark@mit.edu> wrote:
>The files edited in /etc seem to be /etc/motd and /etc/nologin. Either we move
>these files to /var or we accept that DELAYLOGIN and EDITMOTD are implicitly
>false when / is read-only and just hide the errors with 2>/dev/null.

Why. If you setup your system to have a read-only root, which is
already non-standard, it's not really much extra work to edit
/etc/default/rcS and set DELAYLOGIN and EDITMOTD yourself.

>The trickier stuff are the various places that assume /dev is writable. I'm
>not sure these are all solvable. Things like xterm will never work properly if
>they can't set the owner of the pty.

xterm uses Unix98 ptys under /dev/pts, so that should be no problem.
In fact anything should be using that.

>But it still seems odd to me that boot
>scripts are going around doing mknod and chmod on devices.
>
>#
>#	Create mountpoint and multiplexor device.
>#
>[ -d /dev/pts ] || mkdir --mode=755 /dev/pts
>[ -c /dev/ptmx ] || mknod --mode=666 /dev/ptmx c 5 2

That's not a problem - they should be present anyway, and if they
are, nothing is going to happen.

># Set pseudo-terminal access permissions.
>#
>if [ ! -c /dev/.devfsd ] && [ -c /dev/ttyp0 ]
>then
>	chmod 666 /dev/tty[p-za-e][0-9a-f]
>	chown root:tty /dev/tty[p-za-e][0-9a-f]
>fi

That is really needed for old-style ptys to function correctly, but
I guess the errors could be suppressed for a read-only filesystem.
Adding '-f' would solve it. Or, you just remote /dev/tty[p-za-e][0-9a-f]
and /dev/pty[p-za-e][0-9a-f] from /dev and make sure everything
uses Unix98 style pseudo ttys. Everything should, by now.

Mike.
-- 
Anyone who is capable of getting themselves made President should
on no account be allowed to do the job -- Douglas Adams.



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