gnome-screensaver-command -l

gnome-screensaver

gnome-screensaver-command -l

DISPLAY=:0 gnome-screensaver-command -l

mkdir ~/bin

#!/bin/bash
gnome-screensaver-command -l

chmod +x ~/bin/lock

# This file is not read by bash(1), if ~/.bash_profile or ~/.bash_login
# exists.

vim ~/.profile # or one of the the other files if they exist

# set PATH so it includes user's private bin directories
PATH="$HOME/bin:$HOME/.local/bin:$PATH"

you@yourUbuntu:~$ lock