Aptitude on Debian 6.0.4 "media change" to CD ROM

view full story

http://unix.stackexchange.com – I've just installed Debian 6.0.4 on VirtualBox, and I'm trying to install g++. So, into the terminal I typed: aptitude install build-essential But it's trying to get the package from disk: Media Change: Please insert the disc labeled 'Debian GNU/Linux 6.0.4 _Squeeze_ - Official i386 CD Binary-1 20120128-12:53' in the drive '/media/cdrom/' and press [Enter]. Why isn't it just downloading it from Debian's repositories? Can I change this behavior? (HowTos)