How to use the APT command on Ubuntu/Debian Linux systems ?

APT is one of the most frequently used commands in Ubuntu ( and Debian family hereafter ) . APT stands for Advanced Package Tool and is used as a package management (i.e. updating, adding or removing) utility. APT allows you to upgrade an entire set of softwares, applications and packages with a single command ( oftentimes, this will require root level permissions to execute it ). For instance, by invoking the APT command on the gnome-desktop-environment package, will install all the required packages to run the GNOME UI.

In this article you will learn how to manage packages using the APT command. You will be able to install, remove and update software packages by using apt-install and also apt-cache commands.

Syntax of the APT command

In order to know how to use the APT command, open up your terminal and invoke the command :

man apt

This will open up a help file full of information about the syntax and usage of the APT command :

apt command

As we mentioned earlier, not all APT commands are used by all users. Below is a list of the options that can only be run by the root user or via the sudo command .

 A – apt-get command

As mentioned earlier, this command is used to perform installation, removal and upgrade of software packages.

apt command

apt-get update

This will download the latest up-to-date software packages and metadata(package names, version numbers, etc..).this is required for subsequent operations, like upgrade, installation, dependencies, upgrade, etc…

Therefore before an upgrade, an update should be executed. This should be the first command to execute after a fresh install.

This is an example output of this command where you will see some servers from where the information will be retrieved :

image18.png

In the first line in the snapshot above, you will see Hit. This means that there is no change in the package version. If however you see Get, that means a new version is available and that it is going to download its metadata (not the package per se). Sometimes you will notice Ign at the beginning of the line :

IGN and hit in apt command

That means that the package is being ignored (probably was recently updated or there was a trivial error when fetching the information).

You may be interested to read: How to install and uninstall applications in Ubuntu ? A Beginner’s guide

apt-get upgrade

This will upgrade the system to any installed packages having new versions available. This will be based on ( what the update command above did) the recently downloaded metadata. You can also specify the pkg option at the end so that you can choose which package you would like to upgrade. The difference with the update command is that the update command tells the repository database that a new version might be available.

In order to see the packages that can be upgraded , issue the command below :

apt list –upgradable

upgradable

As mentioned above, it is more practical to issue the command below once you install a fresh system : sudo apt-get update && sudo apt-get upgrade -y

apt-get full-upgrade

This will upgrade installed packages and also removes already outdated ones.

apt-get dist-upgrade

It looks for dependencies with the newer version of the package being installed and it tries to install a new package or remove an existing one on its own.

it will attempt to upgrade the most important packages on the expense of the less important ones. This may lead to the removal of some packages which you might not want. This is the main reason why dist-upgrade should be avoided on production machines.

apt-get install package_name

This will install a package along with its dependencies. For example below, we are installing mysql-server package :

mysql server

If for any reason a given package becomes corrupt or stops working then you might want to reinstall it via the command :

apt-get install pkg_name –reinstall

apt-get install pkg_name --reinstall

Using the command:

sudo apt-get install <package_1> <package_2> <package_3>

You will also be able to install many packages at once.

sudo apt-get remove pkg

This will remove the package pkg files but its configuration files and its dependencies will remain.

For example here we are trying to remove the package mysql-server.

rying to remove the package mysql-server.

Since the configuration files will not be suppressed, we would need to use the command with the purge attribute :

sudo apt-get purge mysql-server

sudo apt-get purge mysql-server

Since the dependencies of the installed packages are still around, you can remove them via the command below :

sudo apt-get autoremove

sudo apt-get autoremove

sudo apt-get autoclean

This will clear out the local repository of all the downloaded package files that can no longer be downloaded.

image14.png

You may be interested to read: How to keep Ubuntu clean?


apt-get –download-only source
pkgname

This will only download the source code of a given package.

sudo apt-get source pckgname

This will download and extract the source code of a given package. An example below with the package gparted.

sudo apt-get source gparted

If however you want to download, extract and compile a source code , just issue the command below:

sudo apt-get –compile source pkgname

sudo apt-get --compile source pkgname

apt-get download pkgname

This will download a package without installing it.

image1.png

apt-get check pkgname

This is used for diagnostics. It updates the package list and also checks if there are broken dependencies.

image2.png

apt-get changelog pkgname

This will display the change-log of a package as well as the installed package version. For example the command below will bring up the text file below :

apt-get changelog sudo

apt-get changelog sudo

B – apt-cache command

The apt-cache is used to search software packages and to gather information about them. It can also tell which available packages are ready to be installed on the current distro. No need for superuser privileges here.

apt-cache command

apt-cache search

You will be able to search for packages using this command. Below is an example to search for packages which start with the name mariadb*

apt-cache search

apt-cache show pkgname

This will allow you to display details about a given package, like size, category, version number…

apt-cache show pkgname

apt-cache pkgnames

Will provide a list of all installed packages. Below is a snapshot of the last rows yielded by this command.

apt-cache pkgnames

apt-cache showpkg pkgname

This will show all dependencies of a specified package. In the snapshot below you will see the last rows after execution of the above command for the mysql-server package :

apt-cache showpkg pkgname

apt search command

This is similar to apt-cache search command above.

apt search command

apt list pkgname

This will show the list of all packages or the ones specified in the command line (wildcards can be used).

apt list pkgname

If you add the –all-versions, this will yield all the available versions of all packages.

-all-versions

With the option –installed, it will list all installed packages.

--installed

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