Chmod

A command used to change the access permissions of files and directories on Linux and Unix-like systems.

Chmod (change mode) is a Linux and Unix command used to modify the file system access permissions of files and directories. Linux uses a permission model based on three categories of users: the file owner (user), the group, and others. Each category can be granted read (r), write (w), and execute (x) permissions. Chmod supports two notation styles: symbolic notation (e.g., u+x to add execute permission for the owner) and octal notation (e.g., 755 to set rwxr-xr-x). Proper file permissions are critical for system security, as they control who can read sensitive files, modify configurations, or execute scripts and programs. Chmod is one of the most fundamental commands for Linux system administration and is frequently used alongside chown (change owner) and chgrp (change group).

Users & Permissions

Examples

chmod +x script.sh - Make a script file executable

chmod 755 /var/www/html - Set directory permissions to rwxr-xr-x (owner full, others read and execute)

chmod -R 644 /home/user/docs/ - Recursively set file permissions to rw-r--r-- for all files in a directory

chmod u+rw,go-w file.txt - Add read and write for the owner, remove write for group and others

Related Terms

root sudo bash terminal cli