Early-writeable partition (aka. "/run x /var/run")
Here's a small sinopsys:
1. There is a need for a directory that is writeable *very* early in the
boot process. The alternative is complex and probably far more
undesireable (running daemon that implements a very simplified
filesystem-like interface and keeps all data in memory. Also, modifying
everything to use said daemon -- this will, among other things, slow
down the boot process and add a far more fragile point of failure than a
2. This directory probably should not be generally available in its early
boot location after the equivalent of rcS.d is done with, to avoid
2. Its mountpoint must be somewhere in the / partition, which does NOT mean
directly inside /, it could be inside /etc, /lib or any other directory
that is *always* inside the / partition.
3. 2.4 Linux kernels above and including 2.4.19 and 2.6 can use mount
--move to safely move the directory somewhere else. Debian doesn't
support any kernels before them, so mount --move is available to all
Debian GNU/Linux Etch installs *right now*.
4. Debian supports ephemeral /var/run (i.e. tmpfs /var/run or rm -rf'ed on
early boot /var/run), and failing in a tmpfs /var/run scenario is a bug.
Only two packages still ship /var/run directories inside debs.
5. Adding a new toplevel directory is not to be taken lightly, and faces
a lot of oposition ("/run" proposal).
6. Non-Linux-based Debian systems are supposed to come with their own
best ways to deal with this, but we must make sure our solution can
always be achieved without mount --move, and if at all possible do
so without requiring a *big* / partition.
7. Anything using the early writeable directory must check if it is
there, and if not, try to use something standandard (typically
/var/run) instead. Probably it would be best to FIRST check for
an writeable directory in the standard location, and failing that,
use the new "early writeable directory".
Did I forget anything?
"One disk to rule them all, One disk to find them. One disk to bring
them all and in the darkness grind them. In the Land of Redmond
where the shadows lie." -- The Silicon Valley Tarot