Chmod - What is it?

Chmod stands for Change Mode and is a command often needed for installing scripts (CGI, PHP etc.) on a UNIX server, after uploading the file (with FTP) you may need to change the permissions. Basically it tells the server who can make what changes to the file or folder, i.e. can the script only read the info, or can it write information as into it as well.

What do the Chmod Settings Mean?

Chmod tells the server the access privileges for a file. For example, common file settings are:

777: all can read / write / execute the file.
755: owner can do all, group / others can read / execute.
644: owner can read / write, group / others can read only.

Common Chmod Settings

cgi scripts: 755
data files: 666
configuration files not updated by the script: 644
directories: 777

Chmod Calculator

Some FTP programs give you something that looks like this to set chmod permissions.
This may help you try it out first and find out if you really are setting the right permissions.

chmod (File Permissions) helper
Permission Owner Group Other
Read (r = 4)
Write (w=2)
Execute (x=1)
Octal: =
Symbolic: =