Linux File Permissions Cheat Sheet

Manage file permissions with chmod, chown, and umask commands.

What this cheat sheet is for

This linux file permissions reference helps you complete common developer tasks quickly and avoid repeated trial-and-error when working under deadlines.

When you need a reliable command or pattern during debugging and incident response.
When you are implementing a feature and want a known-good syntax example immediately.
When onboarding teammates and documenting repeatable workflows for daily use.
When reviewing pull requests and verifying that command usage follows best practices.

Change Permissions - chmod

Modify file permissions using numeric mode.

chmod 755 file.txt

Common permission numbers:

777 - rwxrwxrwx (read, write, execute for all)
755 - rwxr-xr-x (owner full, others read+execute)
644 - rw-r--r-- (owner read+write, others read)
600 - rw------- (owner read+write only)

Symbolic notation add permissions:

chmod u+x file.txt       # Add execute for owner
chmod g+w file.txt       # Add write for group
chmod o+r file.txt       # Add read for others
chmod a+x file.txt       # Add execute for all

Remove permissions:

chmod u-w file.txt
chmod go-rwx file.txt

Recursive chmod:

chmod -R 755 directory/

Change Owner - chown

Change file owner and group.

chown user file.txt

Change owner and group:

chown user:group file.txt

Change group only:

chown :group file.txt

Recursive:

chown -R user:group directory/

View Permissions

Display file permissions and ownership.

ls -l file.txt

Output format: -rwxr-xr-x owner group

Permission Symbols

Understanding permission notation:

r = read (4)
w = write (2)
x = execute (1)

First character: file type (- = file, d = directory, l = link)
Next 3: owner permissions (rwx)
Next 3: group permissions (r-x)
Last 3: others permissions (r-x)

Umask

Set default permissions for new files.

umask

Set umask value:

umask 022

Common umask values:

022 - New files: 644, directories: 755
027 - New files: 640, directories: 750
077 - New files: 600, directories: 700

Special Permissions

Setuid bit (run as owner):

chmod u+s file
chmod 4755 file

Setgid bit (inherit group):

chmod g+s directory
chmod 2755 directory

Sticky bit (only owner can delete):

chmod +t directory
chmod 1777 directory

Access Control Lists

View ACL permissions.

getfacl file.txt

Set ACL permissions:

setfacl -m u:username:rwx file.txt

Common mistakes / Pitfalls

People often copy a command or pattern without adapting placeholders, which can break production workflows unexpectedly.
It is easy to forget environment-specific differences, so always verify behavior in your shell, runtime, or API gateway before shipping.
Many errors come from skipping small validation steps, so test with realistic sample input before relying on the result.

Last updated: February 2026