How to manage Linux file permissions

Short answer

Use chmod to change permissions and chown to change ownership of files and directories.

Steps

1. Change permissions numerically:

chmod 755 script.sh

2. Change permissions symbolically:

chmod u+x script.sh

3. Change owner:

chown user:group file.txt

4. Recursively change:

chmod -R 755 /path/to/dir

Tips

• Numeric: read=4, write=2, execute=1. Sum them for each class.
• umask sets default permissions for new files.
• Use ls -l to inspect current permissions.

Common issues

• chmod -R 777 is insecure; prefer minimal necessary permissions.
• Only root can change ownership to another user.