How to Check for Bad Sectors on a Hard Disk in Linux

Let's clarify what constitutes a bad sector or bad block: it's a portion of a hard drive or flash memory that's become unreadable or unwritable, typically due to physical damage to the disk surface or malfunctioning flash memory transistors.

Accumulating bad sectors significantly degrades storage device performance, diminishes capacity, and can ultimately cause complete hardware failure. The presence of bad blocks is a strong indicator that you should consider replacing your drive or, at minimum, marking the affected blocks as unusable.

This article details how to identify bad sectors on your Linux system using disk scanning utilities.

Methods for Detecting Bad Sectors:

1. Using the badblocks Utility:

The badblocks command scans storage devices (hard drives, external drives, etc.) for bad sectors. Device names usually appear as files like /dev/sdc or /dev/sda.

Step 1: Identify Disks and Partitions

First, use fdisk (with root privileges) to list your drives and partitions:

sudo fdisk -l

This output helps you determine the correct device name for scanning.

Step 2: Scan for Bad Blocks

Next, scan your drive for bad sectors:

sudo badblocks -v /dev/sda10 > badsectors.txt

This command scans /dev/sda10 (replace with your device). -v provides verbose output, and the results are saved to badsectors.txt.

If bad sectors are found, unmount the drive and prevent the system from writing to them.

Step 3: Mark Bad Sectors as Unusable

Use e2fsck (for ext2/ext3/ext4 filesystems) or fsck with badsectors.txt:

For ext2/ext3/ext4:

sudo e2fsck -l badsectors.txt /dev/sda10

For other filesystems:

sudo fsck -l badsectors.txt /dev/sda10

2. Using smartmontools (Recommended):

This is a more reliable method, especially for modern drives (ATA/SATA, SCSI/SAS, SSDs) with S.M.A.R.T. (Self-Monitoring, Analysis, and Reporting Technology). S.M.A.R.T. helps detect and report drive health.

Step 1: Install smartmontools

Install using your distribution's package manager:

sudo apt install smartmontools  # Debian/Ubuntu
sudo dnf install smartmontools  # Fedora/RHEL/CentOS

Step 2: Use smartctl for Health Checks

smartctl interacts with the drive's S.M.A.R.T. system. Review its manual page:

man smartctl
smartctl -h

Step 3: Run a Basic Health Test

Run a basic health check:

sudo smartctl -H /dev/sda10

A healthy drive will show a positive result.

Optional: View Full SMART Report

For a complete report, use:

sudo smartctl -a /dev/sda10  # All SMART attributes
sudo smartctl -x /dev/sda10  # All SMART and non-SMART data

Conclusion:

This guide demonstrates how to detect and manage bad sectors using badblocks and smartmontools. Regularly monitoring your storage health is essential, and these tools simplify the process. If you have any questions, please comment below.

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