Validating Linux umask settings

The umask setting determines the permissions of newly created files and directories. If you plan to install IBM FCI graph analytics on a VM, you must ensure that the umask for the root account and all newly created users is set to the system default of 0022 on all servers during the installation. After installation is completed, you can modify the umask value to be more restrictive or permissive, as required. Note that the higher the umask value, the more restrictive it is (for example, 027 is more restrictive than 0022).

Important: Ensure that the umask value includes two zeros (00). Even though a value of 022 is equivalent to 0022, installation will fail with a umask value of 022.

IBM FCI contains several components, which require a umask value of 0022 during installation. IBM FCI must also be installed using the root user ID. This combination (umask value and user ID) is the default setting for many Linux® distributions. However, a local system administrator might change the default umask value.

Procedure

To test the default umask value:

  1. Open a Terminal session and log in as the root user, or enter sudo su root to become root. If logged in as another user, enter sudo su root -c umask.
    Note: Create a test user:
    useradd -m -U testumask
    Then, create a new login shell to become the new user:
    su - testumask
  2. From a Terminal session, enter the following command:
    umask
  3. If the value returned is not 0022, consult your system administrator to have the default value changed back to 0022.
    Note: On RHEL, the default umask is stored in the /etc/bashrc file, where the umask for user accounts with UIDs of 200 and higher is 002, and UIDs less than 200 (typically administrator and system accounts) is 022.
    The umask value is usually set in one of the following locations:
    
    /etc/profile   
    /etc/bashrc 
    /etc/.bash_profile    
    /root/.bashrc   
    /root/.bash_profile
  4. Return to the root prompt and enter the following command:
    exit
    Note: Delete the test user that you created in Step 1:
    userdel -r testumask