Badblocks
badblocks is a utility that checks for bad blocks on a storage device.
This is useful for testing new or questionable media including fake USB drives that show as a larger drive than it can actually store. It's also useful for testing new hard drives (before the warranty expires) or checking if a older drive is reliable. Be forewarned - larger disks takes a very long time to test.
Basic Usage
The destructive test can be done by running:
## Warning! This will wipe your data!
# badblocks -wsv -o /root/badblocks.txt /dev/sda
Use the -n flag for a non-destructive test. A non-destructive test will store the sector value, test the sector, then restore the original sector value.
There are 3 numbers that will be returned as 1/2/3 in this order:
- number of read errors
- number of write errors
- number of corruption errors
The badblocks.txt file that gets created can then be used by mkfs so that the filesystem can skip over known bad sectors like so:
# mkfs.ext4 -l /tmp/badblocks.txt /dev/sda
Creating a filesystem around bad blocks
Most filesystems can take a file containing a list of all bad blocks and work around it. To do so, create the partitions and then run badblocks against each partition, then create the filesystem.
Eg:
# fdisk /dev/sdb
## Make your desired partitions
# badblocks -wsv -o /tmp/badblocks.txt /dev/sdb1
# mkfs.vfat -l /tmp/badblocks /dev/sdb1
In some cases, the bad blocks may be positioned such that the filesystem cannot be created. If you really want to get the device working, you can try moving the partition around so that the bad blocks don't interfere with the filesystem.
Other Information
Test Patterns
The test that is done by default is to write to the disk in 4 passes, each with the following pattern:
- 0xAA - 10101010
- 0x55 - 01010101
- 0xff - 11111111
- 0x00 - 00000000
You may override this using the -t flag.