Whatever you do, do not run the following command:
mv /lib /test-lib
# mv /lib /test-lib
# mv /test-lib /lib
/bin/mv: No such file or directory
# ln -s /test-lib /lib
/bin/ln: No such file or directory
# perl -e 'rename "/test-lib", "/lib"'
/usr/bin/perl: No such file or directory
/sbin/reboot: No such file or directory
I think you can see where this is going...
Of course, on reboot you can't even get as far as running init, even if you set init=/bin/sh. I hope you have a good boot floppy.