Managing Software

By the end of this section, you should understand:

1. Package Management: Modern Linux distributions use package managers like apt for software management, similar to app stores on mobile devices.
2. APT Basics: Essential commands include apt update to refresh the package list, apt upgrade to install available updates, and apt install to add new packages.
3. Installing Software: Besides apt, software can also be installed from source, as .deb packages with dpkg, or as snap, flatpak, or appimage packages for broader compatibility.
4. Maintaining Your System: Use apt autoremove to clean up unused dependencies, and apt clean or apt autoclean to clear out cached packages to free up disk space.
5. Package Information: Use apt show for package details, apt policy for version information, and apt search to find packages by name or keyword.
6. Removal Options: apt remove uninstalls packages, while apt purge also removes configuration files.
7. Script Automation: Common update and cleanup tasks can be automated with a bash script and run with sudo for ease of use.
8. APT Logs: Review apt activity by checking /var/log/apt/history.log.
9. Manual Reading: For deeper understanding, consult the man apt manual page.

Getting Started

Many modern Linux distributions offer some kind of package manager to install, manage, and remove software. These package management systems interact with curated and audited central repositories of software that are collected into packages. They also provide a set of tools to learn about the software that exists in these repositories.

If package management seems like an odd concept to you, it's just a way to manage software installation. It's very similar to the way that Apple and Google distribute software via the App Store and Google Play.

APT

On Debian based systems, which includes Ubuntu, we use apt, apt-get, and apt-cache to manage most software installations. For most cases, you will simply want to use the apt command. It is meant to combine the functionality commonly used with apt-get and apt-cache.

DPKG

We can also install software from source code or from pre-built binaries. On Debian and Ubuntu, we can install (if we trust it) pre-built binaries distributed on the internet as .deb files. These are comparable to .dmg files for macOS and to .exe files for Windows. When installing .deb files, we generally use the dpkg command, although it's possible to use apt to install these files, too.

Source Code

Installing software from source code often involves compiling the software. It's usually not difficult to install software this way. However, it can become complicated to manage software that's installed from source code simply because it means managing dependencies. This means we would need to manually track new patches or versions of the software.

Snap, Flatpak, and AppImage

Another way to install software is to use snap or flatpak systems or appimage files. These are newer ways of packaging programs that involves packaging a program and all of its dependencies as self-contained packages. The main audience seems to be aimed at IoT, embedded devices, and desktop/laptop systems. If you see loop devices in the output of the lsblk command, this is the result of the snap system. See the Snap, Flatpak, and AppImage sites for example applications.

Language Package Managers

In addition to the above, some programming languages provide their own mechanisms to install packages. In many cases, these packages may be installed with the apt command, but the packages that apt will install tend to be older (but more stable) than the packages that a programming language will install. For example, Python has the pip or pip3 command to install and remove Python libraries. The R programming language has the install.packages(), remove.packages(), and the update.packages() commands to install R libraries.

Despite all these ways to install, manage, remove, and update software, we will focus on using the apt command, which is pretty straightforward.

Using APT

Let's look at the basic apt commands.

apt update

Before installing any software, we need to update the index of packages that are available for the system. We do so with:

sudo apt update

apt upgrade

When we update the package index, we will be informed if we need to upgrade any packages. If any upgrades are available, we run the following command:

sudo apt upgrade

apt search

We may know a package's name when we're ready to install it, but we also may not. To search for a package, we use the following syntax, replacing [package name] with search terms:

apt search [package-name]

Package names will never have spaces between words. Rather, if a package name has more than one word, each word will be separated by a hyphen.

In practice, say I'm curious if there are any console based games:

apt search ncurses game

I added ncurses to my search query because the ncurses library is often used to create console-based applications.

apt show

The above command returns a list that includes a game called ninvaders, which is a console-based Space Invaders like game. To get additional information about this package, we use the apt show [package-name] command:

apt show ninvaders

If we want to see what a package needs or depends on, then we can use the following command:

apt-cache depends ninvaders

apt policy

To get a list of various versions that are available to download, we can use the apt policy command:

apt policy ninvaders

apt install

It's quite simple to install the package called ninvaders:

sudo apt install ninvaders

apt remove or apt purge

To remove an installed package, we can use either the apt remove or the apt purge commands. Sometimes when a program is installed, configuration files get installed with it in the /etc directory. The apt purge command removes those configuration files but the apt remove command does not. Both commands are offered because sometimes it is useful to keep those configuration files.

sudo apt remove ninvaders

Or:

sudo apt purge ninvaders

Other fun terminal based games include: tint (a tetris clone), ttysolitaire, and bsdgames, the latter installs multiple console based games such as backgammon, go-fish, hangman, and more. All of these will be installed in /usr/games`.

apt autoremove

All big software requires other software to run. This other software are called dependencies. The apt show [package-name] command will list a program's dependencies, as well as the apt-cache depends command. However, when we remove software when using the apt remove or apt purge commands, the dependencies, even if no longer needed, are not necessarily removed. To remove them and restore disk space, we do:

sudo apt autoremove

apt clean or apt autoclean

When we install software using the apt command, the installed packages are stored locally. We don't necessarily need those once the binaries have been installed. Or we may want to remove them especially if we're removing the binaries. The apt clean and apt autoclean commands clear up that local cache of packages. We use either of these commands to free up disk space.

Between the two, the apt clean command removes all package files that are stored in /var/cache/apt/archives. But the apt autoclean only removes package files that can no longer be downloaded. I generally use the apt clean command to free up more disk space. I will only use apt autoclean if I want to keep an package to older software, but this is rare.

To use:

sudo apt clean

Or:

sudo apt autoclean

apt history

Unfortunately, the apt command does not provide a way to get a history of how it's been used on a system. This will change in the future when apt gets a apt history-list command and an apt history-info command (Source: Phoronix). In the meantime, the apt system keeps a log of its activity, and we can review that log file with the following command:

less /var/log/apt/history.log

Daily Usage

This all may seem complicated, but it's really not. For example, to keep my systems updated, I run the following four commands on a daily or near daily basis:

sudo apt update
sudo apt upgrade
sudo apt autoremove
sudo apt clean

You can add these commands to a script that we could call update.sh and put it in /usr/local/bin:

#!/usr/bin/env bash

apt update && apt upgrade && apt autoremove && apt clean

And then we make the file executable:

sudo chmod 700 /usr/local/bin/update.sh`:

And execute/run it with the following command:

sudo update.sh

Conclusion

There are a variety of ways to install software on a Linux or Ubuntu system. The common way to do it on Ubuntu is to use the apt command, which was covered in this section.

We'll come back to this command often because we'll soon install and setup a complete LAMP (Linux, Apache, MariaDB, and PHP) server. Until then, I encourage you to read through the manual page for apt:

man apt