I just installed ubuntu 11.10 on my computer, my problem is that after I configure the afs client , I lost my admin password and root password. Do have any idea to recover my password?
No, when you lose these passwords you are at the point of no return. Putting a backdoor in would be a huge security flaw and so that's why there isn't one. Boot from a livecd and copy all your data to somewhere safe, then reinstall Ubuntu and copy it back. That's the best you can do.