Linux chattr Command with Practical Examples

Introduction

In this lab, we will learn about the Linux chattr command, which is used to change the attributes of files and directories. We will explore how to use the chattr command to set and remove various file attributes, such as the immutable attribute that prevents a file from being deleted or modified. We will also see practical examples of using the chattr command to protect important files and directories.

The lab covers the following steps:

1. Understand the chattr command and its common options.
2. Modify file attributes using the chattr command, including setting the immutable and append-only attributes.
3. Protect important files with the immutable attribute.

Linux Commands Cheat Sheet

Skills Graph

Understand the chattr Command

In this step, we will learn about the chattr command in Linux, which is used to change the attributes of a file or directory. The chattr command allows you to set or remove various file attributes, such as the immutable attribute, which prevents a file from being deleted or modified.

First, let's explore the basic syntax of the chattr command:

sudo chattr [options] [files]

The most common options used with chattr are:

• + - Add the specified attribute(s)
• - - Remove the specified attribute(s)
• i - Set the immutable attribute
• a - Set the append-only attribute
• s - Set the secure deletion attribute
• u - Set the undeletable attribute

Now, let's see some examples of using the chattr command:

## Set the immutable attribute on a file
sudo chattr +i file.txt

## Remove the immutable attribute from a file
sudo chattr -i file.txt

## Set the append-only attribute on a directory
sudo chattr +a ~/project/logs

## Remove the append-only attribute from a directory
sudo chattr -a ~/project/logs

Example output:

## Set the immutable attribute on a file
$ sudo chattr +i file.txt

## Remove the immutable attribute from a file
$ sudo chattr -i file.txt

## Set the append-only attribute on a directory
$ sudo chattr +a ~/project/logs

## Remove the append-only attribute from a directory
$ sudo chattr -a ~/project/logs

The chattr command is a powerful tool for managing file and directory attributes in Linux. In the next step, we will explore more practical examples of using the chattr command.

Modify File Attributes Using chattr

In this step, we will explore how to use the chattr command to modify file attributes in more detail.

First, let's create a sample file to work with:

touch ~/project/file.txt

Now, let's set the immutable attribute on the file:

sudo chattr +i ~/project/file.txt

Example output:

$ sudo chattr +i ~/project/file.txt

With the immutable attribute set, the file cannot be deleted, renamed, or modified, even by the root user. Let's try to delete the file:

rm ~/project/file.txt

Example output:

$ rm ~/project/file.txt
rm: cannot remove '~/project/file.txt': Operation not permitted

As you can see, the rm command failed to delete the file due to the immutable attribute.

Next, let's set the append-only attribute on a directory:

sudo chattr +a ~/project/logs

Example output:

$ sudo chattr +a ~/project/logs

With the append-only attribute set, files in the ~/project/logs directory can only be appended to, not modified or deleted. Let's try to create a new file and append some text to it:

echo "New log entry" >> ~/project/logs/log.txt

Example output:

$ echo "New log entry" >> ~/project/logs/log.txt

However, if we try to modify the file, the operation will be denied:

echo "Modifying log" > ~/project/logs/log.txt

Example output:

$ echo "Modifying log" > ~/project/logs/log.txt
-bash: ~/project/logs/log.txt: Operation not permitted

In this step, you learned how to use the chattr command to set the immutable and append-only attributes on files and directories, respectively. These attributes can be useful for protecting important files and logs from accidental or unauthorized modifications.

Protect Important Files with Immutable Attribute

In this final step, we will learn how to use the immutable attribute to protect important files from being accidentally or maliciously modified or deleted.

Let's start by creating an important file that we want to protect:

echo "This is an important file" > ~/project/important.txt

Now, let's set the immutable attribute on the file:

sudo chattr +i ~/project/important.txt

Example output:

$ sudo chattr +i ~/project/important.txt

With the immutable attribute set, the file cannot be deleted, renamed, or modified, even by the root user. Let's try to delete the file:

rm ~/project/important.txt

Example output:

$ rm ~/project/important.txt
rm: cannot remove '~/project/important.txt': Operation not permitted

As you can see, the rm command failed to delete the file due to the immutable attribute.

Next, let's try to modify the file:

echo "Trying to modify the file" > ~/project/important.txt

Example output:

$ echo "Trying to modify the file" > ~/project/important.txt
-bash: ~/project/important.txt: Operation not permitted

Again, the operation is not permitted because the file has the immutable attribute set.

To remove the immutable attribute and allow modifications, you can use the following command:

sudo chattr -i ~/project/important.txt

Example output:

$ sudo chattr -i ~/project/important.txt

Now, you can freely modify or delete the file.

The immutable attribute is a powerful tool for protecting important files and directories from accidental or malicious changes. By setting this attribute, you can ensure that critical system files, configuration settings, or sensitive data remain intact, even in the face of user errors or security breaches.

Summary

In this lab, we learned about the Linux chattr command, which is used to change the attributes of files and directories. We first explored the basic syntax and common options of the chattr command, such as setting the immutable, append-only, and secure deletion attributes. Then, we practiced modifying file attributes using the chattr command, including setting the immutable attribute to protect important files from being deleted or modified. Overall, the chattr command is a powerful tool for managing file and directory attributes in Linux.

Linux Commands Cheat Sheet