Attempts to recover a hard disk that has bad blocks on it.
WARNING: A hard disk with bad blocks on is likely to fail! If you value your data you should get a new hard disk instead of using this program!
However, if you can't afford a new hard disk, or just like being reckless with your data then this tool might just help you out!
You can download the latest version here.
First of all, if you haven't already got it - go download smartmontools! Then run:
smartctl -A /dev/hda
where hda is whichever drive you're interested in. The output should include three attributes that are interesting:
Reallocated_Event_Count
This is how many sectors have already been reallocated on the drive. We're hoping to get the hard disk to increase this number!
Current_Pending_Sector
The number of sectors that the drive thinks are dodgy. Bear in mind sometimes drives change their mind about whether a sector is bad or not - so this number can go down without a reallocation occuring.
Offline_Uncorrectable
This is the number of sectors that the drive has attempted to correct itself, but failed. Running the command:
smartctl -t offline /dev/hda
should cause the drive to test the sectors and attempt to fix them. Not all drives support this though.
So the attribute you're interested in at the moment is Current_Pending_Sector. If this is not 0 then there's something up with your disk. If Offline_Uncorrectable is less than Current_Pending_Sectors then you may want to run an offline test which may fix it, or you can dive straight in and use hdrecover which will test (and attempt to fix) it itself.
So run (as root):
hdrecover /dev/hda
and sit back and wait (or probably you're best off going and doing something else while you wait). If the program comes across a bad sector it will make several attempts at reading the sector. Between each attempt it will randomly seek so as to reposition the head, hopefully getting the data off the disk. If it succeeds then the drive should automatically reallocate the sector. If after several attempts the data still can't be read then the program will give you the option of overwriting the data in the sector. This will force the drive to reallocate the block.
WARNING: Overwriting the sector WILL cause data loss (it's fairly obvious really!). Hopefully, since it is only one sector (or a handful if there are more bad sectors on the drive), it won't be too important. But bear in mind that you should at the very least run fsck to check the integrity of the filesystem.
Once the program has finished (it takes a long time I'm afraid), a summary will be printed showing how many blocks had errors. If you repeat the smartctl command:
smartctl -A /dev/hda
you should see that Current_Pending_Sector is now 0 and Reallocated_Event_Count will have risen by the number of sectors the drive decided to reallocate. Offline_Uncorrectable usually doesn't immediately update - you have to either wait for the drive to update it itself or run an offline test which should force the drive to update it.
Have fun!
DISCLAIMER: Hard disks with bad sectors could fail at anytime - although hdrecover appears to fix the drive you shouldn't trust it! And just to re-inforce the GPL licence: if it in any way breaks your computer then you get to keep both pieces! I accept no responsibility for any damage it causes!