Configure the APT Package manager

Check The Network Connection

Although you've succeed the installation, you cannot do anything without configuring your source of your package manager.

Most Debian-based systems provied a powerful package manager called Advanced Packaging Tool, or APT. We can easily use apt-get command to install/remove open-source software in the Debian repository.

Before starting the configuraion, check the network connection in advance:

$ ping www.gooogle.com

If you receive something like, it mean your connection is well:

PING www.google.com (74.125.203.105) 56(84) bytes of data.
64 bytes from th-in-f105.1e100.net (74.125.203.105): icmp_seq=1 ttl=46 time=15.6 ms
64 bytes from th-in-f105.1e100.net (74.125.203.105): icmp_seq=2 ttl=46 time=15.4 ms
64 bytes from th-in-f105.1e100.net (74.125.203.105): icmp_seq=3 ttl=46 time=15.6 ms

Setup Archive Mirror Repository to Your Server

Open /etc/apt/source.list We will use vi to edit source.list. If you are not familiar to vi, use nano to substitube for vi in the command.
```
$ sudo vi /etc/apt/source.list
```
For an archieve mirror of Debian 8 (jessie) repository, simply add following lines into sourece.list.
```
deb http://<favourite-debian-mirror>/debian/ jessie main
deb-src http://<favourite-debian-mirror>/debian/ jessie main
```
NOTE: You need to substitute <favourite-cran-mirror> by one of the mirror URLs listed in the mirror list. For example: deb http://debian.csie.ntu.edu.tw/debian/ jessie main

Comment out the sources from CD/DVD In the source.list file, there are some CD/DVD sources reserved for dealing some situation without network in the future.
For now, they are useless and should be commented out:

# deb cdrom:[Debian GNU/Linux 8.2.0 _Jessie_ - Official amd64 CD Binary-1 20150906-11:13]/ jessie contrib main
# deb cdrom:[Debian GNU/Linux 8.2.0 _Jessie_ - Official amd64 CD Binary-1 20150906-11:13]/ jessie contrib main

After all the commands above, you can install whatever your want in the Debian Repository.

Let's learn some useful apt-get command:

apt-get update: This command can resynchronize and update all packages from the sources. For security issue, ensure you update your server regulariry.
apt-get install/remove: These command can simply install/remove packages you specified.
apt-get auroremove: After you remove some pakcages, you may want to execute this command for clean all the dependency.

Configure the APT Package Manager