Virtual Private Server User Guide

Internet and UNIX Basics

Changing File and Directory Permissions

Users can modify the permissions on files or directories they own by using the 

chmod command. Regular users cannot modify the permissions of files or 

directories that they do not own. Members of the sysadmin group, however, can 

use the vchmod super command to modify the permissions on files and 

directories that are owned by other users, except for those owned by the user 

root. The root user, also known as the superuser, can change the permissions on 

any file using the chmod command.

Whether using the chmod or the vchmod command, you can set permissions 

explicitly using the permissions number system, or by assigning individual 

permissions based on the user type. Examples of each method are given below.

Example 1: Setting permissions via the permission numbering system

Suppose you want exclusive read, write, and execute permissions to a file called 

 all.mine,  which you own. According to the numbering system, the corresponding 

number would be 700. To set these permissions, use the following command:

>  chmod 700 all.mine

You can verify the permissions by issuing the ll command. The resulting output 

displays the following permissions on the all.mine file:

 rwx      

Example 2: Giving yourself permission to execute a file that you own:

Each type of user can be represented by one of the following values:

u    The user who owns the file (usually you)

g    Members of the group to which the owner belongs   

o    Other users

a    All users (includes u, g, o)

Using the "+" symbol indicates the adding of a permission, and using i i indicates 

the removal of a permission.

So, to give the owner permission to execute a file, use the following syntax:

chmod u+x file1

This gives you execute permission for the file "file1". 

Example 3: Giving members of the file's group permission to write to the 

file:

chmod g+w file2

This gives the group permission to write to the file "file2".

Example 4: Giving read permission to all users for a particular type of file: 

(The a includes "all" groups: u, g, o)

Technical Training Department

August 2004

1 12