badblocks

Additional Notes

badblocks scans a block device for unreadable or unreliable blocks. It is a low-level diagnostic tool and can be destructive when used with write-mode tests.

Use it carefully when checking failing disks, preparing old drives, or feeding bad-block information into filesystem tools.

Syntax

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

Parameters

• device: Block device such as /dev/sdb or /dev/sdb1.
• last-block: Optional ending block.
• first-block: Optional starting block.
• options: Read-only, write-mode, block-size, and output controls.

Common Options

• -v: Verbose output.
• -s: Show progress.
• -n: Non-destructive read-write test. Still risky on unhealthy disks.
• -w: Destructive write-mode test. Erases data.
• -o FILE: Write bad block list to a file.
• -b SIZE: Set block size.
• -c NUM: Number of blocks tested at a time.

Examples

sudo badblocks -sv /dev/sdb

Run a read-only scan with progress.

sudo badblocks -sv -o badblocks.txt /dev/sdb

Save bad block locations to a file.

sudo badblocks -wsv /dev/sdb

Run a destructive write test. This erases data.

Practical Notes

• Double-check device names with lsblk before running this command.
• Do not run destructive tests on a disk containing data you need.
• SMART tools such as smartctl are often better for health diagnosis.