How to Change File Permissions in Absolute Mode

1. If you are not the owner of the file or directory, become superuser or assume an equivalent role.

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

2. Change permissions in absolute mode.

   % chmod nnn filename

   nnn

   Specifies the octal values that represent the permissions for the file owner, file group, and others, in that order. For the list of valid octal values, see Table 7–4.

   filename

   Specifies the file or directory.

   ---

   Note –

   When you use the chmod command to change the file group permissions on a file with ACL entries, both the file group permissions and the ACL mask are changed to the new permissions. Be aware that the new ACL mask permissions can change the permissions for other users and groups who have ACL entries on the file. Use the getfacl command to make sure that the appropriate permissions are set for all ACL entries. For more information, see the getfacl(1) man page.

   ---

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

   % ls -l filename

Example 7–4 Changing Permissions in Absolute Mode

In the following example, the permissions of a public directory are changed from 744 (read, write, execute; read-only; and read-only) to 755 (read, write, execute; read and execute; and read and execute).

# ls -ld public_dir
drwxr--r--  1 ignatz   staff    6023 Aug  5 12:06 public_dir
# chmod 755 public_dir
# ls -ld public_dir
drwxr-xr-x  1 ignatz   staff    6023 Aug  5 12:06 public_dir

In the following example, the permissions of an executable shell script are changed from read and write to read, write, and execute.

% ls -l my_script
-rw------- 1 ignatz   staff    6023 Aug  5 12:06 my_script
% chmod 700 my_script
% ls -l my_script
-rwx------ 1 ignatz   staff    6023 Aug  5 12:06 my_script