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I have Ubuntu Lucid with kernel 2.6.35 on a Thinkpad T61. In the power management settings I set it up to blank the display after 2 minutes. This works right after I log in, but after a few hours of active use, closing applications and then walking away from the computer, the display won't ever blank until I log out and log in again. The screensaver, although enabled, activates only in the first few hours after logging in.

What can be the root cause of the problem?

  • Incorrect screensaver or blanking settings cannot be the root cause, because these features work with the current settings right after logging in.

  • User-visible applications (such as Firefox, Chrome, their Flash player or Skype) cannot be the root cause, because the screen doesn't blank even after I quit these. (Verified with ps ax.)

Is there a workaround?

How do I debug the problem? Is there a tool which displays a counter like 1:57 seconds until blanking?

Please note that in this question I don't care about sleep, suspend or hibernate -- I care only about blanking the display.

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up vote 1 down vote accepted

I've searched for hours and found two ways:

Bash Scripts: Here is a thread that has 2 ways. Post #7 is when the answers begin:

Easier way: Stop using gnome-power-manager:

  1. Install xfce4-power-manager
  2. Don't do anything to gnome-power-manager. Keep it in your system and ignore it like an annoying classmate. If you uninstall it, it will uninstall vital Ubuntu components.
  3. Go to System > Preferences > Startup Applications
    • Find: Power Management and click Edit. Change: gnome-power-manger to xfce4-power-manger. Save. (If you add in a custom Startup Applications entry for xfce4-power-manager, it may not start. Don't know why that happens. Editing the original Power Management is more reliable.)
  4. Hit Alt-F2 and run command xfce4-power-manager-settings. Change the settings.
  5. Reboot.
  6. Downside:
    • The screen will darken/turn off during video apps because gnome-screensaver does not tell xfce4-power-manager to inhibit itself during video playback.
    • If the xfc4-power-manager works, but is unreliable, you might want to upgrade to version 1.0+ using this ppa: ppa:alexx2000/xfce
    • If that still doesn't work, change gnome-screensaver to xscreensaver.
    • If that still doesn't work, use my last option: Spend more than a week trying out different OSes, give up, and upgrade to Ubuntu/Gnome-Shell 11.10. This problem has been solved there. Interestingly, Ubuntu 11.10 uses xscreensaver and not gnome-screensaver.
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Thank you for this well-researched answer. I always wanted to get rid of gnome-power-manager, but I didn't know my options to replace it with. – pts Mar 11 '12 at 8:03

You could start by checking that gnome-screensaver is still running:

[user@host] ~> ps ax |grep screen
 1939 ?        Ss     0:06 gnome-screensaver

If it is running kill it with 'kill [pid]' and restart it with 'gnome-screensaver --debug'

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