How to Manage Users and Permissions in Linux
Managing users and file permissions correctly is essential for a secure multi-user server.
Managing users
sudo adduser alice # create a user
sudo usermod -aG sudo alice # grant sudo
sudo passwd alice # set/change password
sudo deluser alice # remove a userUnderstanding permissions
Each file has read (r), write (w) and execute (x) permissions for owner, group and others. ls -l shows them, e.g. -rwxr-xr--.
Changing permissions and ownership
chmod 755 script.sh # rwxr-xr-x
chmod +x script.sh # make executable
chown alice:developers file.txt # change owner:group
chmod -R 775 /var/www/app # recursivePermission numbers
- 7 = read + write + execute
- 6 = read + write
- 5 = read + execute
- 4 = read only
Grant the minimum permissions needed — avoid chmod 777.
