LIBPATH (was Re: /usr/etd/biod 0 'is very bad for your health'

[marc at arnor.uucp]

The safe way to test a new version of libc.a is to 

mount /whatever/libc.a /lib/libc.a

and see if it works.  This will cause all subsequent uses of libc.a
to be the new one BUT, if you crash and reboot you're back to the old
one.

The safe way to replace libc.a is:

cd /lib
cp libc.a libc.a.orig (if you don't already have a backup IN /lib
cp /whatever/libc.a libc.a.new
sync
mv libc.a.new libc.a

mv is atomic - you'll either have the new or the old even if you crash
right then and there.

It is possible to fix libc.a if you've trashed it.

boot from diskettes.

/etc/continue hdisk0 exit

which stops the start up before anything is mounted.

you can then mount /dev/hd4 someplace and restore libc.a.  (At that
point, there is a copy in /lib/libc.a (from the diskette) which will
work.)  Make sure the diskettes are at the same level as the machine.