system administrators: those who lose data when this happens and those who
have good schemes in place. Be forewarned and be wise.
If you cannot boot a drive and do not have a backup, which happens to most
system administrators only once in their lives (because they learn from the
mistake), immediately stop messing with the hard drive. Your best bet to
recover the data will be very expensive, but you should look for a company
that specializes in the task and pay them to do it. If your data is not worth the
expense for recovery and you want to try to recover it yourself, you can try,
but this is not a task for the faint of heart, and more often than not, the data is
simply lost. Again, the best course is to backup regularly, check your backups
to be sure they are valid, and repeat. Practice restoring from backups before
you need to do it, perhaps with a test system that is not vital and will not hurt
anything if you make a mistake.
References
https://help.ubuntu.com/community/BackupYourSystem—An
excellent place to start for learning and examining backup methods in
Ubuntu
http://www.tldp.org—The Linux Documentation Project, which offers several
useful HOWTO documents that discuss backups and disk recovery