Linux: How to fix Media change: please insert the disk labeled 'Debian GNU/Linux'

This is one of the problems of newbie in Linux and one of the problems in Debian when installing an application. This is important to know because /etc/apt/sources.list is commonly used file in Debian world. So, In this tutorial we are going to solve this problem.

1. Edit the /etc/apt/sources.list. I'm using vi for editing files, because this is one of the most powerfull editor in the planet. But you can use your own preferred text editor like sublime text editor or gedit or notepad++.  

editing the /etc/apt/sources.list

2. Find the line 'deb cdrom: [Debian GNU/Linux 8.x.x XXX]'. You need to find this line because this causes the error 'please inset the disk'. Again, if you are familiar with vi editor, you need to go to the beggining of the line so that we will trigger some steps at number 3.

3. Comment out the line  'deb cdrom: [Debian GNU/Linux 8.x.x XXX]'.  When commenting out using vi editor, all you need is to press the 'i' and press the '#'.  This means that your are now commenting out or disregarding out the line. After that you can now test installing a package.