Use cron in ubuntu to remind you to rest

In ubuntu, cron is used to remind you to take a break. When windows was used, iegis is used to remind you to get up for an hour and change to ubuntu, so I want to use cron to directly remind myself to take a rest. The principle is very simple. I will lock the screen once every hour. DISPLAY =: 000 *****/usr/bin/gnome-screensaver-command -- lock note the preceding DISPLAY =: 0. If this variable is not available, gnome-screensaver-command will not take effect, an Error will be reported: Failed to get session bus: Error spawning command line 'offline-launch -- autolaunch = 903fc0c1b3535fe8f55930a05120822c -- binary-syntax -- close-stderr ': Child process exited with code