As printed on the front cover of the hitch hikers guide to the galaxy, in bold red letters
Don't Panic
Ok the first thing you need to do is change root of rescue to the root of your file system (basically make all paths relative to /, by:
root@mech_client ~]# chroot /path/to/your/filesystem/root
The rescue disc should tell you where it has mounted your file system (usually under /mnt somewhere), then see if find works in rescue mode by typing
root@mech_client ~]# find / -name usr
this should find all files with usr in them and print them to the screen. If this works it is a relatively easy thing to restore your /usr directory. Then once you have found your /usr/and/everything/else directory tree back it up just in case. If you have a memory stick (size of 1G or more should do), mount it
root@mech_client ~]# mount -t vfat /dev/memstick_device /mnt
Substitute the /dev/memstick_device with the actual device file that the kernel attaches to the memorystick (dmesg will tell you what it is),and do a
root@mech_client ~]# cp /path/to/usr /path/to/mounted/memory/stick/
then cd to the directory where your usr directory is and then type
root@mech_client ~]# mv /path/to/usr /
then do a
root@mech_client ~]# ls -la /
to make sure everything is back where it should be. Once everything is back to where it should be, reboot and see if it all boots again. If not something else may be amiss as well!
If it boots ok, make yourself a non privileged account where you can't do this again
btw the unix root file system looks like this (FC 6, but yours should be basically the same):
[root@mech_client ~]# ls /
bin dev home lost+found misc net proc sbin srv tmp var
boot etc lib media mnt opt root selinux sys usr
Good luck, hope this helps
