Linux fsck.ext2 Command with Practical Examples

Introduction

In this lab, we will explore the Linux fsck.ext2 command, which is used to check and repair ext2 file systems. The lab covers the introduction to the fsck.ext2 command, how to check and repair an ext2 file system, and how to perform a forced file system check. The fsck.ext2 command is part of the e2fsprogs package, which provides a set of utilities for managing ext2, ext3, and ext4 file systems. The lab includes practical examples and step-by-step instructions to help users understand the usage and capabilities of the fsck.ext2 command.

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Introduction to the fsck.ext2 Command

In this step, we will learn about the fsck.ext2 command, which is used to check and repair the ext2 file system in Linux. The fsck.ext2 command is part of the e2fsprogs package, which provides a set of utilities for managing ext2, ext3, and ext4 file systems.

The fsck.ext2 command is used to perform a file system check and repair on an ext2 file system. It can be used to check for and correct file system inconsistencies, such as missing blocks, incorrect file sizes, and other errors that can occur due to power failures, system crashes, or other issues.

Let's start by checking the version of the fsck.ext2 command installed on our system:

fsck.ext2 --version

Example output:

fsck.ext2 1.46.5 (30-Dec-2021)

The fsck.ext2 command can be used with various options to perform different tasks, such as:

• -a: Automatically repair the file system without prompting the user.
• -f: Force a file system check, even if the file system appears to be clean.
• -v: Display verbose output during the file system check.
• -y: Assume "yes" to all questions.

We'll explore some of these options in the next steps.

Checking and Repairing an ext2 File System

In this step, we will learn how to use the fsck.ext2 command to check and repair an ext2 file system.

First, let's create a test file system using the dd command:

sudo dd if=/dev/zero of=test.img bs=1M count=100
sudo mkfs.ext2 test.img

This will create a 100 MB ext2 file system image named test.img.

Now, let's check the file system using the fsck.ext2 command:

sudo fsck.ext2 test.img

Example output:

test.img: clean, 11/25600 files, 7236/102400 blocks

The output shows that the file system is clean, with 11 files and 7,236 blocks.

Next, let's intentionally corrupt the file system by deleting a few blocks:

sudo dd if=/dev/zero of=test.img bs=1M count=1 seek=50

This will overwrite the 50th 1 MB block of the file system with zeros, causing a file system error.

Now, let's try to check and repair the file system:

sudo fsck.ext2 -a test.img

Example output:

test.img: ***** FILE SYSTEM WAS MODIFIED *****
test.img: 11/25600 files (0.0% non-contiguous), 7236/102400 blocks

The -a option tells fsck.ext2 to automatically repair the file system without prompting the user. The output shows that the file system was modified during the repair process.

Performing a Forced File System Check

In this final step, we will learn how to perform a forced file system check using the fsck.ext2 command.

Sometimes, the file system may appear to be clean, but it's still a good idea to perform a forced check to ensure that there are no underlying issues. This can be done using the -f option.

Let's start by creating another test file system:

sudo dd if=/dev/zero of=test2.img bs=1M count=100
sudo mkfs.ext2 test2.img

Now, let's perform a forced file system check:

sudo fsck.ext2 -f test2.img

Example output:

test2.img: clean, 11/25600 files, 7236/102400 blocks

As you can see, the file system is reported as clean, even though we didn't intentionally corrupt it.

However, let's say we want to perform a more thorough check, just to be sure. We can use the -v option to display verbose output:

sudo fsck.ext2 -f -v test2.img

Example output:

test2.img: ***** FILE SYSTEM WAS MODIFIED *****
test2.img: clean, 11/25600 files, 7236/102400 blocks

The verbose output shows that the file system was modified during the check, even though no issues were found. This can be useful for troubleshooting and ensuring the integrity of the file system.

Summary

In this lab, you learned about the fsck.ext2 command, which is used to check and repair the ext2 file system in Linux. You started by exploring the command's version and available options, then proceeded to create a test ext2 file system and intentionally corrupt it. You then used the fsck.ext2 command to check and repair the file system, demonstrating its ability to detect and fix issues. Finally, you performed a forced file system check to ensure the integrity of the file system, even if it appeared to be clean.

The lab provided a practical understanding of the fsck.ext2 command and its use in maintaining the health of ext2 file systems in Linux.

Linux Commands Cheat Sheet