System Administration Guide: Security Services

How to Change Permissions in Symbolic Mode

Use the following procedure to change permissions in symbolic mode.

  1. If you are not the owner of the file or directory, become superuser.

    Only the current owner or superuser can use the chmod command to change file permissions on a file or directory.

  2. Change permissions in symbolic mode by using the chmod command.

    $ chmod who operator permission filename

    who operator permission

    who specifies whose permissions are to be changed, operator specifies the operation to be performed, and permission specifies what permissions are to be changed. For the list of valid symbols, see Table 16–7.


    Specifies the file or directory. 

  3. Verify that the permissions of the file have changed.

    $ ls -l filename

Examples—Changing Permissions in Symbolic Mode

In the following example, read permission are taken away from others.

$ chmod o-r filea

In the following example, read and execute permissions are added for user, group, and others.

$ chmod a+rx fileb

In the following example, read, write, and execute permissions are assigned to group.

$ chmod g=rwx filec