Understanding Linux File Attributes

In Linux, beyond UGO/RWX permissions and ACLs (Access Control Lists), file and directory attributes add an extra layer of control over how system programs and users interact with files. These attributes help secure, manage, and customize file behavior, providing additional control over critical system and user files.

Let’s begin by exploring how to view file attributes, then dive into some commonly used attributes and learn how to set or remove them.

Viewing File Attributes with lsattr

To check the attributes of files and directories, you can use the lsattr utility. This command is typically included in the e2fsprogs package, which is standard on most Linux distributions.

To list attributes for all files in the current directory:

$ lsattr

--------------e------- ./Videos
--------------e------- ./Music
--------------e------- ./hello
--------------e------- ./visual-studio-code-bin
--------------e------- ./Downloads
--------------e------- ./config-2
--------------e------- ./book.png
--------------e------- ./Pictures
--------------e------- ./first-steps-with-linux
--------------e------- ./logs
----i---------e------- ./demo

The output of lsattr shows attributes that are set on a file, like e (for extents) or - (indicating an unset attribute). In addition to e, you may also see flags like i, a, and d, which we will cover in the next section. The lsattr output provides a quick way to verify which attributes are active on each file or directory.

To list attributes for a specific file or directory:

$ lsattr Downloads

--------------e------- Downloads/nord.png
--------------e------- Downloads/2024-10-03_20-17.png
--------------e------- Downloads/progress.png
--------------e------- Downloads/fstab.png
--------------e------- Downloads/config
--------------e------- Downloads/nord2.png
--------------e------- Downloads/ascii.png

When you run lsattr on a directory, it will display the attributes for each file within that directory, giving a detailed view of individual file settings.

If you want more readable output that displays attributes in word form rather than single letters, you can use the -l option. For example:

$ lsattr -l demo

demo/configs                 Immutable, Extents
demo/deployment.yaml         Immutable, Extents
demo/packages.json           Immutable, Extents
demo/data.txt                Immutable, Extents
demo/notes.pdf               Immutable, Extents
demo/shitgrep                Immutable, Extents
demo/shitgrep.c              Immutable, Extents
demo/hel.bak                 Immutable, Extents
demo/shitcd.c                Immutable, Extents
demo/shitcd                  Immutable, Extents
demo/dockerfile              Immutable, Extents
demo/hello.bak               Immutable, Extents
demo/config.conf             Immutable, Extents

With lsattr -l, the attributes are displayed in full words (e.g., "Immutable" and "Extents") instead of abbreviations. This can make it easier to understand at a glance which attributes are applied to each file or directory.

Managing File and Directory Attributes

File and directory attributes can be managed using the chattr command. Let’s go through a few essential attributes and see how they work.