Ubuntu OS must allow users to directly initiate a session lock for all connection types.

A session lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system but does not want to log out because of the temporary nature of the absence.

The session lock is implemented at the point where session activity can be determined. Rather than be forced to wait for a period of time to expire before the user session can be locked, Ubuntu OS need to provide users with the ability to manually invoke a session lock so users may secure their session if they need to temporarily vacate the immediate physical vicinity.

Satisfies: SRG-OS-000030-GPOS-00011, SRG-OS-000031-GPOS-00012

Verify Ubuntu OS has the "vlock" package installed by using the following command:

     $ dpkg -l | grep vlock 
     ii     vlock     2.2.2-10     amd64     Virtual Console locking program 

If "vlock" is not installed, this is a finding.

Install the "vlock" package by using the following command:

     $ sudo apt-get install vlock