让ubuntu安装build-essential时不从光盘安装

安装sudo apt-get install build-essential时，会提示：
Media change: please insert the disc labeled
'Ubuntu 8.04.2 _Hardy Heron_ - Release i386 (20090121)'
in the drive '/cdrom/' and press enter
 
可以安装下面的方法解决：
you need to edit your sources file.
Of course you should always make a backup first.
Code:

sudo cp /etc/apt/sources.list sources.list.bak

At the top you will see a line that starts like:

deb cdrom: blah blah blah


put a # infront of it. Then save.

来自：http://ubuntuforums.org/showthread.php?t=436647