Re: [uml-devel] mconsole telinit design, worry about init standards?

[Jeff Dike <jdike@addtoit.com>]

dan@shearer.org said:
> I've got a rough implementation of an mcsonole telinit command, where
> mconsole_kern opens /dev/initctl and sends a command to change
> runlevels.

cameron@patrick.wattle.id.au said:
> How about having some kind of generic interface to allow the host to
> access files, send signals, etc inside the VM?

Sorry, but none of these handy things are going into the kernel.  If you want
to run processes, open files, etc, you can do all that from userspace.

I see the following possibilities:

	Log in and run the command - some people don't like to write scripts
to go through the login process, so you can
	Have a dedicated console which just has a root shell running on it.  I
think there will be people who object to parsing shell prompts, so they can
	Send the command through /proc/mconsole to a script which does

	while true; do cmd=read < /proc/mconsole; `$cmd >& /proc/mconsole`; done

This last requires that /proc/mconsole be made bidirectional, plus it requires
that script running inside UML.  All of these require some amount of setup
beforehand (knowledge of the root password, inittab running a shell instead of
getting on one console, the /proc/mconsole script).  

All of them are also subject to interference by a hostile root inside the
UML.  However, the in-kernel proposals can be subverted by root as well (change
init to not obey initctl, move files around, etc).

				Jeff




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