System-wide power management policy on debian-based distros?

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http://unix.stackexchange.com – I would like to put idle machines in our lab (running Mint Debian edition) on standby after a timeout. I have tried pm-suspend and it puts the machines on standby and wakes up fine. Does anybody know how to set a system-wide power policy that will be in force when no user is logged in? I've tried packages like laptop-mode-tools but it doesn't offer a suspend timeout. Ideally this should be completely independent of desktop environment. The only solution I found by googling is to hack a GDM logout hook with xautolock calling pm-suspend after a timeout. (HowTos)