How to Set ACL Permissions Using setfacl

Permissions and Ownerships

How to Set ACL Permissions Using setfacl

Welcome to this beginner-friendly Linux tutorial! Today, we're going to learn how to use setfacl to apply Access Control Lists (ACLs) on files and directories.

ACLs allow you to give specific users or groups custom permissions on top of the traditional owner-group-others model. Super useful when you want to allow more than one user access to a file or directory — with different permission levels!

Step 1: Create a Directory and File

Let’s begin by creating a sample directory and a file.

mkdir acl_demo
cd acl_demo
touch report.txt

Step 2: View Default Permissions

ls -l report.txt
-rw-r--r-- 1 user user 0 Jul  2 10:00 report.txt

Right now, only the file owner (you) can write to this file. Others can only read it.

Step 3: Grant Write Permission to Another User Using setfacl

Suppose we want to give write permission to another user, say alice.

setfacl -m u:alice:w report.txt

Here’s what this means:

  • -m means modify ACL
  • u:alice:w means give user 'alice' write access

Step 4: Check the Updated ACL

getfacl report.txt
# file: report.txt
# owner: user
# group: user
user::rw-
user:alice:-w-
group::r--
mask::rw-
other::r--

Now you can see that alice has write permission!

Step 5: Give Multiple Permissions (Read + Write)

setfacl -m u:alice:rw report.txt

Check again:

getfacl report.txt
user:alice:rw-

Step 6: Set Default ACLs on a Directory

If you want every new file in a directory to inherit ACL permissions automatically:

setfacl -d -m u:alice:rw acl_demo

The -d flag sets default ACLs.

Step 7: Remove ACL for a User

setfacl -x u:alice report.txt

This removes all ACL permissions for user alice from report.txt.

Step 8: Remove All ACLs

setfacl -b report.txt

This command removes all ACL entries and resets the file to standard permissions.

Bonus: Check if ACLs are Enabled

To check if your filesystem supports ACLs:

tune2fs -l /dev/sdX | grep "Default mount options"

Replace /dev/sdX with your actual disk device.

That's It!

Now you know how to use setfacl to grant specific permissions to different users in Linux.

This is especially useful in shared environments and multi-user systems.

Practice with sample files and explore combining ACLs with traditional permissions for powerful control.


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