Linux chmod Command Explained

In Linux world, file permission is a vital issue. Unlike other OS (e.g. Microsoft Windows or MAC OS) Linux and Unix count file permission as a vital issue.

In a Linux box, 'chmod' command is used to change permission of any file, folder or even any device (Linux Operating System count every device as file).

To use 'chmod' command, you can find the basic information from Linux 'man'(Manual) page, by typing following command:

#man chmod

A combination of the letters ‘ugoa’ controls which users’ access to the file will be changed:

the (u)ser who owns it (u),
other users in the file’s (g)roup (g),
(o)ther users not in the file’s group (o), or all users (a).

If none of these are given, the effect is as if ‘a’
were given, but bits that are set in the umask are not affected.

The chmod command also consider permission level in numerical way. You will see a lot of reference in Internet to change your file permission in value '755' where numeric value is count as bellow:

Read Permission: 4 (Four)
Write Permission: 2 (Two)
Execute Permission: 1 (One)

Details of Linux chmod Command Explained Here...