FOUR ESSENTIAL COMMANDS

learn about APT and apt-get.

Goal of this lesson:

To be familiar with these fours commands are very important for this course.

They are:

$ apt-get update
$ apt-get upgrade
$ apt-get install/ remove
$ nano

This may be the most boring chapter of this series, but it is kind of the most important one. Please try to go through it!

What is Command-line:

A command is text written in a specific syntax. After entering a command into a terminal, the shell of your OS interprets and passes it to the OS to execute.

Some commands only available for power user. You will need to be the root user or to use sudo.

Why do we use command-line a lot in this tutorial? Because we are building our operating system from the ground up. Most of the time we will not have the luxury of GUI.

Moreover, relying on GUI is not a healthy attitude in my opinion, command line actually is a powerful tool that will help you on every aspect of Linux.

Apt and the source.list file:

Apt (short for Advanced Package Tool) is a set of core tools inside Debian. Apt makes it possible to:

• Install applications
• Remove applications
• Keep your applications up to date
• And much more…

Apt, which basically resolves dependency problems and retrieves the requested packages.

(from Debian wiki)

Apt frees you from the madness of specifying each of dependencies when installing an application.

In an Linux OS, various applications may simultaneously need the same dependencies. Apt will keep the harmony between them by keeping only the appropriate version.

/etc/apt/source.list

This file is listing the sources where packages are being stored so that apt can know where to obtained them. These sources are called repositories.

The four commands:

1. Update repositories

   sudo apt-get update
   

   This is the most essential command of apt-get. What it does is to go to the addresses listed in the /apt/etc/source.list file and update what have been changed from the last time you update repositories (which packages are on there now and which are the latest versions of them). After that apt will have the newest information and can ask for the right version of packages. Otherwise, error will occur because the version of the package asked (old info) is not matching with the one that currently is on repositories.

2. Install or update a specific package

   sudo apt-get install firefox
   

   This command will also update the firefox package if it has been already installed.

3. Remove a package

   sudo apt-get remove firefox
   

   To also remove all of firefox’s configuration files on your system add the flag –purge:

   sudo apt-get remove --purge firefox
   

4. Edit text file using Nano editor Nano lets you edit text file directly from the terminal which is very handy because in a Linux system, configuration files are all text files. To edit a text:

   sudo nano /directory/configuration_file
   

   Please use the navigation keys (up/ down/ left/ right arrows) to navigate through the file and edit it. After making the changes, Ctrl + X to close nano editor, it will ask you to save, type “Y” to confirm, or type “N” to abort.