damaged /usr partition

[Ruth Milner]

In v7n77, Our Moderator writes:

[[ If /usr is on its own partition, you don't even have to mess with the
"mini-root", just boot single user.  In order to do this, however, you
need to have made a dump of your /usr partition in the recent past.  But
you should be doing that periodically anyway.  --wnl ]]

This is fine for 3.X systems. However, under 4.0, *all* executable images
which used to  be in /etc now are just symlinks to the corresponding
programs in /usr/etc. This includes such vital commands as ifconfig,
newfs, mkfs, dump, and - charmingly - restore. When the system boots
single-user, both / and /usr are pre-mounted and available. So if your 4.0
/usr is trashed, unless you have put copies of those images in /etc to
replace the links, you have no choice but to boot the mini-root to restore
your /usr dump(s). And even then, you have to watch out for programs which
call other programs (e.g. newfs runs mkfs).

This has got to be the thing I dislike most about 4.0. In order for your
system to boot, it is now totally dependent on two partitions instead of
one, so there are two crucial points of filesystem failure (three if you
count swap). Yuck.

Ruth Milner
Systems Manager
University of Toronto Physics

sysruth at helios.physics.utoronto.ca