When managing files on your hosting account, you'll encounter chmod (short for "change mode"). This is a command-line utility used to set file and directory permissions on Unix-like systems, including Linux servers. Permissions control who can read, write, or execute a file.

Permissions are defined for three user classes:

• Owner (u): The user who owns the file.
• Group (g): Other users in the file's group.
• Others (o): All other users on the system.

Each class can be granted different levels of access, represented by a three-digit octal number (like 755) or a symbolic code (like u+rwx).

Common Permission Examples:

• 755: Owner can read, write, execute; Group and Others can only read and execute. Ideal for scripts and directories.
• 644: Owner can read and write; Group and Others can only read. Standard for web files (HTML, CSS).
• 777: Warning: Grants read, write, execute to everyone. Avoid this for security.

To change permissions via SSH, use: chmod 755 filename. In your hosting control panel's File Manager, you can usually set permissions with a click.

Setting correct permissions is crucial for security and functionality. Incorrect settings can make your site vulnerable or cause scripts to fail. When in doubt, consult your script's documentation or start with restrictive permissions (like 644) and increase only as needed.