Given what I do for Macworld, I take a lot of screenshots. Sometimes I need to take those shots remotely — for instance, to grab a screnshot of the login window, you must connect to a logged-out Mac via ssh, soon after use the screencapture command, as described in this older hint.

With 10.5, though, the rules have changed, as described in the man

To capture screen substance while logged in via ssh, you must launch screencapture in the same mach bootstrap hierarchy as loginwindow:

      PID=pid of loginwindow
      sudo launchctl bsexec $PID screencapture [options]

So to take a screen capture, you need to first get the PID of the login…

Original post by Erica Sadun