It is not [Was: Re: ifupdown writes to /etc... a bug?]
I finaly went and looked at ifup/down to fix the writing to /etc
iussue and saw the following in the changelog:
ifupdown (0.6.4-4) unstable; urgency=low
* Don't delete /etc/network/ifstate every boot, just empty the file. This
way people can symlink it to /var/run/ifstate if they so desire (ie, if
/var is local and /etc is read-only). (Closes: Bug#103868, Bug#85206)
* Explicitly set PATH in the environment, because pdksh is broken, broken
I say. (Closes: Bug#83557, Bug#99444)
-- Anthony Towns <email@example.com> Tue, 19 Jun 2001 00:04:30 +1000
So ifup/down is already ready for /mem and a read-only /.
lvm2 is next.