How to fix the hard-drive Bad Sector

A bad sector on a drive is a sign of permanent damage to the drive. Unless you have reason to believe that your drive marked these sectors as bad incorrectly, you cannot "fix" them.

It means that a part of your drive is damaged to the extent that it can no longer reliably be read from and/or written to.

Your system can continue to use the drive by marking that sector as unusable, but if you have enough bad sectors, or a SMART tool triggers a warning level, you might consider a drive replacement, as bad sectors can be a sign that more sectors, or the whole drive, might fail soon.

While there may be ways to force the drive to un-mark a sector as bad, allowing you to use it again, this is likely not a good idea. The sector may stay good, but it will just as likely become bad again. Some data may be lost or corrupted depending on how it fails.

Now, as for the error message you've pasted in your question (as of my writing this), that error has nothing to do with bad sectors. It means that you don't have access to the drive. Being sudo can give you access, so:

sudo fsck /dev/sdb

However, this is still probably not what you want, because /dev/sdb refers to the entire drive, whereas fsck is designed to work on filesystems, which are usually (but not always, and you may have an exception here) placed in partitions. If the above didn't work, you may instead have wanted to do this to the 1st partition on that drive:

sudo fsck /dev/sdb1

You can get a list of partitions per drive with:

sudo fdisk -l

In short: Boot a rescue system and use badblocks:

badblocks -svn /dev/sda

to have the hard disk controller replace bad blocks by spare blocks.

I have answered the same question in detail here.

In the olden days you used to have to take a note of the badblocks that were written on the drive and enter those in the defect list before formatting the drive, because hard disk surfaces were never "perfect", manufacturer's got wise to this because people buying disks would look at the defect table printed on the disk and buy the ones with the least amount of defects...

Now scroll forward 20 or so years and hard disk manufacturers hide the fact a brand new disk has bad blocks with the firmware, when you buy a brand new disk it will have in all probability bad blocks already, the firmware will detect newly grown badblocks and maps them out from a set of spare cylinders it has, but this only happens when a write operation occurs on that sector and the ECC algorithm detects bit failure, only then will it map the block out. So getting back to the point you can force a drive to map out the badblocks by simply using DD, ie/ [edit: following example was edited to prevent accidental drive destruction: removed wildcard character, replaced with X]

dd if=/dev/zero of=/dev/sdX bs=1M 

obviously alter the of=target to reflect the drive you want to zero this is the quickest way to re-map a drives defects, its also the quickest way to totally trash your Linux setup by getting the target drive wrong, so check, double check then check again, before you press the enter key. You can increase the size of the blocksize in the dd command to optimize read/writes and perhaps make things go quicker, but there are diminishing returns after a point. I find anything between 1M and 8M works best for me

You can get DD to just write one sector, the bad one... to get it remapped, so you don't have to backup your drive, but that's a whole different kettle of fish and Russian roulette if you don't know exactly what you're doing .....

This command WILL destroy everything on your hard drive including any partitions. But it will force the drive to map out any bad sectors it may have.

It is perfectly ok for a disk to have bad sectors as long as they aren't on the boot sector, if they are then the drive is useless, if you notice a few months later that your drive has developed more bad sectors then it's time to start shopping for a replacement.

I've revived hundreds of drives like this and they've lived on for many years afterwards, a bad sector isn't necessarily the death knell for the drive.