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Laptop-mode is said to be one of the energy efficiency boosters for Linux. Now, sources I found say that to activate you need to:

  1. install laptop-mode-tools
  2. append LAPTOP_MODE_ENABLED=true (if it doesn't exist; otherwise make sure that it's set to true) inside /etc/default/acpi-support

However, even after doing this laptop mode is not running (I have it set up in /etc/laptop-mode/laptop-mode.conf to be always on):

~$ cat /proc/sys/vm/laptop_mode 
0

Does anyone know how can I enable laptop-mode?

It is mentioned here that the Ubuntu package is "crippled". Is it really the case that Ubuntu doesn't allow you to enter this mode on AC? If so, why?

Edit - it seems that laptop-mode is not necessary any more since Ubuntu 12.04, according to this question.

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1  
I have laptop mode enabled on my system though –  Mysterio Aug 26 '12 at 17:34
    
Laptop mode magically started working without me changing anything, so I guess the above steps are sufficient. I must have not rebooted enough times (or I maybe just did a log off - log on and that isn't enough). –  kermit666 Aug 27 '12 at 19:19
    
See also: askubuntu.com/questions/172391/… –  Jorge Castro Aug 29 '12 at 16:06

3 Answers 3

up vote 6 down vote accepted

The steps listed in the question are correct, the only thing remaining is to reboot your machine (possibly a couple of times). After that laptop mode will be enabled:

~$ cat /proc/sys/vm/laptop_mode 
2

Once laptop-mode is working, you can follow these steps to configure laptop-mode...

Edit /etc/laptop-mode/laptop-mode.conf and change

ENABLE_LAPTOP_MODE_ON_AC=0

to

ENABLE_LAPTOP_MODE_ON_AC=1

Also check for the battery mode on battery state and turn it on if it is off by changing the value to 1

e.g.: ENABLE_LAPTOP_MODE_ON_BATTERY = 1

You can set many other option in this config file (the file has many self-explanatory comments). You should try setting them to your liking.

When you're done, restart laptop-mode with:

sudo /etc/init.d/laptop-mode restart

P.S. If laptop-mode is still not on after rebooting the machine, you can try playing with this command as well to manually enable it:

Check that it's active on AC with for example:

$ sudo laptop_mode start

which should output:

Laptop mode 
enabled, 
active [unchanged]

Hope this helps..

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Thanks for the tips about configuring laptop-mode. I also picked those settings in laptop-mode.conf. Just take care to have the LAPTOP_MODE_ENABLED=true inside /etc/deffault/acpi-support so that you don't have to turn it on manually every time - it seems this does work in the end. –  kermit666 Aug 27 '12 at 19:22
    
please what line is this setting on inside the acpi-support file? –  Mysterio Aug 28 '12 at 5:58
1  
I appended it to the end of the file, because it didn't exist in my acpi-support file. Take a look at the original question, I edited it to be more clear. –  kermit666 Aug 29 '12 at 14:29

enter root by

sudo su

and then

echo 5 > /proc/sys/vm/laptop_mode

If you want more tips to save power check out LessWatts. I was able to extend my battery life from 2 hours to 3 and a half.

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Thanks for the tip, though I think echoing to /proc is a temporary solution - one would have to repeat it after every system boot. See my comment to the original question, I got the acpi config file method working after all. –  kermit666 Aug 27 '12 at 19:26
    
nope. when you do it as root, it sets it permanently. –  Schweinsteiger Aug 27 '12 at 20:56
    
OK, well then this is another method of doing it. –  kermit666 Aug 29 '12 at 14:19

In Lubuntu Menu choose Preferences -> Default applications for LXSession -> Settings -> Laptop mode -> yes

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