Ignore bad sector on ext4 file system without formatting?

Question

UDisk shows the assessment on my disk

Disk is OK, 19 bad sectors (24° C / 75° F)

This number has remained unchanged for one years long, so I guess my disk is not going to fail, but bad sectors cause my system to crash. Can my Ext4 filesystem ignore them without formatting?

Answer 1

Yes, your ext4 filesystem can ignore them without formatting.

But unless you have a really really old harddisk, you'll probably have a harddisk that automatically re-allocates bad sectors to "spare" sectors on the next write, all transparently to the OS.

So the proper way is to get a bad block list, try to read each of those several times just in case, and then write it back (or zero it if you can't read it; in that case you might also want to identify the file, and see if you can't restore it from somewhere). You can do this e.g. with dd (but double check everything before you hit return, it's easy to do stupid things with dd and direct writes to hard drives or partitions).

While you are at it, also check the SMART data of your harddrive with smartctl.

Answer 2

You can run fsck.ext2 with the -c option, which will run badblocks, create an invisible file with the blocks that fail to read, and then make sure that no two files share the same blocks. If any of these blocks are in use by another file, this shows up as a conflict, and you are given various repair options like trying to duplicate the blocks, or deleting the file.

That kind of repair cannot be performed during an automatic (-a) run, because it involves a destructive operation. If you combine -c and -a, the file system check can fail, and I'm not sure if the bad blocks inode is properly constructed in that run (it should be, so you should be able to then do an interactive repair without repeating the scan).

That way, these blocks are marked as allocated and will not be used.