screenshot of lightdm login screen (debian jessie)

I was trying to get a screenshot of my lightdm login screen after I'd added Openbox to Debian Jessie Xfce. The steps I used:

First, I installed ImageMagic. From a terminal in an Xfce session, I ran:

# apt-get install imagemagick

Next, I created the file ~/screenshot.sh, with the following inside:

chvt 7; sleep 5s; DISPLAY=:0 XAUTHORITY=/var/run/lightdm/root/:0 xwd -root -out ~/screenshot.xwd; convert ~/screenshot.xwd ~/screenshot.png; rm ~/screenshot.xwd

(In the above, chvt 7 is the number of the virtual console. It takes a screenshot 5 seconds after the script has been run and saves the screenshot to the home directory.)

Then, I made the script executable.

Then, to take the screenshot, I logged out of the system, pressed Ctrl+Alt+F1 at the login screen to go to console mode, logged in as the normal user, got root access, and ran the screenshot script:

# ./screenshot.sh

Once the script ran, it took me back to the login screen and after five seconds it took the screenshot and saved it in the /root directory with the filename screenshot.png. (I then copied screenshot.png to my home directory.)

To do this, I (somewhat loosely) followed the steps I found in this article: How To Take Screenshot Of Login Screen In Ubuntu 14.04