laptop screen always shutdown if no keyboard interaction for several minutes

Ian Smith smithi at
Tue Jan 23 13:11:47 UTC 2007

   Re: freebsd-questions Digest, Vol 162, Issue 5
 > Message: 3
 > Date: Tue, 23 Jan 2007 16:47:02 +0800
 > From: Zhang Weiwu <zhangweiwu at>

 > Hello. I tried various ways to stop the laptop screen from being
 > shutting down, as I use this screen to watch debug message of an
 > application I am working on, I need monitor always on, no screensaver,
 > no blank, no dpms etc.

What make and model laptop?

 > I cannot do it. I have tried:
 >      1. set blanktime to "NO" in /etc/rc.conf
 >      2. set saver to "NO" in /etc/rc.conf

On my Compaq 1500c, saver only affects it while viewing a vty; I use
apm_saver which actually does power down my screen.  In X (KDE) saver
has no effect, and I usually have KDE's power management turned off. 

 >      3. start X server and run a terminal in it, run xset -dpms

What window manager?  KDE, for instance, can do its own screensaver
management, that could override or bypass your manual -dpms setting.

 >      4. check laptop BIOS setting (there is no setting for automatic
 >         blank time

Your BIOS surely has settings for power management, both for battery and
mains power?  These might include screenblanking even if it's not called
that (eg maximum / minimum / no power savings or such)? 

Apart from manually invoked suspend/resume and battery state reporting,
apm relies on (and is oblivious to) the machine's BIOS APM settings for
blanking / disk off / suspend timers, or does on my 1500c at least.

 > I have not tried:
 >      I. remove 'apm' from kernel (I didn't compile ACPI into kernel
 >         because this is an old notebook I am not sure if ACPI works, but
 >         I have compiled apm in kernel, which is not shown in dmesg and
 >         doesn't seem to work, e.g. 'shutdown -p' do not turn off the
 >         power)

Usually - given we don't know what sort of old laptop - you can or must
specifically enable or disable APM and/or ACPI in BIOS.

If apm is not shown in /var/run/dmesg.boot then it isn't being used, or
perhaps not detected.  checking dmesg after booting verbosely might give
at least some clue about that, assuming that APM is enabled in BIOS. 

Boot to the loader prompt and check that hint.apm.0.disabled=0 and that
hint.apm.0.flags="0x20" (a safe default).  You could then 'boot -v' to
get your verbose dmesg.boot, which you may want to save for reference.

 >     II. install Windows on the same computer to see if Windows can keep
 >         the monitor on.

Hopefully it hasn't come to that, yet :)

 >    III. boot the system to FreeDOS and see if monitor keep turned up (to
 >         decide if LCD is turned off by hardware or software)

Sounds like an easy non-destructive test from a floppy or CD boot.

 > Any suggestions?

Provide some basic info.  Somebody else might know the same machine. 

Cheers, Ian

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