How to manage file permissions in Linux

Linux permissions control who can read, write or execute a file. Many "Permission denied" errors and security risks come from wrong permissions.

How to read them

ls -l

A line like -rw-r--r-- means: the owner reads and writes, the group and others only read.

chmod: change permissions

chmod 644 file        # owner rw, others r
chmod 755 script.sh   # owner rwx, others rx
chmod 600 secret      # owner only

chown: change the owner

chown www-data:www-data /var/www/site
chown -R user:user /home/user/data

Good rules

• Web files: 644, directories: 755.
• Private keys and secrets: 600.
• Never use 777, it gives full access to anyone.

Web applications

The web server (usually www-data) must own the application's files. Wrong permissions cause 500 errors, see deploying Laravel to production.