Here is a very simple tip that will allow you to save some power and hence extend your battery life (on laptops and netbooks) on your Linux system. Typically in a Linux graphical environment like GNOME or KDE, whenever we insert a CD or DVD into your CD/DVD-ROM drives, a window pops open automatically showing the contents of CD or DVD.

Disabling auto polling

Although it is a cool feature but it comes with some cost – your computer program like HAL in this case has to typically poll the CD-ROM drive every few seconds to see if there is CD inserted or not and this process causes some extra power consumption. With all the “Going Green” hoopla present around us, let’s us see how we can tell hal to stop polling for the CD-ROM device like this:

#hal-disable-polling --device /dev/cdrom

Output:
Following symlink from /dev/cdrom to /dev/scd0.
Polling for drive /dev/cdrom have been disabled. The fdi file written was
/etc/hal/fdi/information/media-check-disable-storage_model_iHAS120___6.fdi

Now when you insert your CD/DVD drive, you will no longer see the automatic pop-up window and your SATA/PATA power savings are in effect!

Typically your /dev/cdrom is symlink to your actual CD-ROM device like this:

#ls -l /dev/cdrom
lrwxrwxrwx 1 root root 4 2009-07-06 06:53 /dev/cdrom -> scd0

Enabling back auto polling

Now to enable back the polling of your CD-ROM drive give the following command:

# hal-disable-polling --enable-polling --device /dev/cdrom

Output:
Following symlink from /dev/cdrom to /dev/scd0.
Polling for drive /dev/cdrom have been enabled. The fdi file deleted was
/etc/hal/fdi/information/media-check-disable-storage_model_iHAS120___6.fdi

Now when you insert your CD/DVD, the window will pop open automatically as it use to do before.

Happy Polling!

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