NixOS must provide the capability for 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, operating systems need to provide users with the ability to manually invoke a session lock so users may secure their session should the need arise for them to temporarily vacate the immediate physical vicinity.

Satisfies: SRG-OS-000030-GPOS-00011, SRG-OS-000028-GPOS-00009, SRG-OS-000031-GPOS-00012

Verify the NixOS operating system has the "vlock" package installed by running the following command:

$ which vlock /run/current-system/sw/bin/vlock

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

Configure NixOS to have a package that allows user to lock session.

Update the NixOS config, typically stored either in /etc/nixos/configuration.nix or /etc/nixos/flake.nix:

environment.systemPackages = [ pkgs.vlock ];

Rebuild and switch to the new NixOS configuration: $ sudo nixos-rebuild switch