badblocks

Scan devices for bad disk blocks

TLDR

Check device for bad blocks (read-only)

$ badblocks -v [/dev/sdb]

Destructive write test

$ badblocks -wsv [/dev/sdb]

Non-destructive read-write test

$ badblocks -nsv [/dev/sdb]

Save bad block list

$ badblocks -o [badblocks.txt] [/dev/sdb]

SYNOPSIS

badblocks [options] device [last-block] [first-block]

badblocks searches a device for bad blocks by performing read, write, or non-destructive read-write tests. It's used to verify disk integrity and create lists of bad blocks for filesystem tools.
The tool is particularly useful for testing new drives or diagnosing failing storage devices.

PARAMETERS

-v

Verbose mode

-w

Destructive write test (erases data)

-n

Non-destructive read-write test

-s

Show progress

-o file

Output bad blocks to file

-b size

Block size in bytes (default: 1024)

-c blocks

Number of blocks to test at once

-p passes

Number of test passes

-t pattern

Test pattern (random or specific value)

TEST MODES

Read-only (default)

Safe, detects existing bad blocks

Write (-w)

Destructive, thorough testing, erases all data

Non-destructive (-n)

Safe, reads then writes back original data

WORKFLOW

$ # Check for bad blocks (safe)
sudo badblocks -sv /dev/sdb

# Create bad block list for e2fsck
sudo badblocks -o badblocks.txt /dev/sdb
sudo e2fsck -l badblocks.txt /dev/sdb

# Thorough destructive test (WARNING: erases data)
sudo badblocks -wsv /dev/sdb

CAVEATS

Write modes DESTROY all data on the device. Requires root privileges. Very slow on large drives (hours or days). Modern drives remap bad sectors automatically. Non-destructive mode still carries small risk of data loss. SMR drives may show poor performance during testing.