Basic Data Recovery in Linux
First thing to do is "Don't Panic!" You can recover lost files and perform basic data recovery in Linux with ease following these instructions.
Most, if not all, filesystems will only delete the reference to the file from the partition table. This means that the data is still available but the link to it has gone and that it is possible to easily undelete files. It is very important that you do not write any more information to the drive the files were on as the new data could overwrite the file you want to recover, making the data recovery process much more difficult.
If the files to undelete are on your boot drive then you should remove the hard drive and access it from another PC. If it isn't possible to do this then you should be very careful and do not install any software or download any files to it. Try and get hold of a data recovery CD or Live CD and boot from that instead.
Fortunately this time the files I deleted were on a secondary partition not the boot partition. Rather than remove the drive, I was able to remount it read-only.
sudo mount -o remount,ro /mystorage/
The linux partition is now mounted readonly so the data should be "safe".
Next, create a directory on another drive which will hold the recovered files.
sudo mkdir /mystorage2/recovery
I'm going to be using ext undelete for this as the files were on an EXT4 filesystem. If ext undelete is not installed you can (under Ubuntu) run the following command to install it. Other distributions may have slightly different commands.
sudo apt-get install extundelete
Once it has been installed, you can run the command to recover all files to the current directory.
sudo extundelete /dev/dm-4 --restore-all
Where /dev/dm-4 is the partition device.
After about 5 minutes, but depending on the size and quantity of data, any files that can be recovered will restored to the local path. You can now remount the filesystem read-write and save the files back to their original directory.
Slap yourself on the wrist and don't do it again!