Bash comes pre-installed with many essential programs. But when you need to install other tools a package manager can make the process fast and easy. While we will not be doing any local development in Bash and Linux we will eventually configure remote VMs in Azure. To that end we will be working with the apt package manager in the Ubuntu VM for practice before venturing into the cloud.
The Ubuntu Distribution comes pre-installed with the Advanced Packaging Tool (apt) program for managing packages. We will focus on the commands that are used most frequently. Like most CLI programs you can view more details about how to use apt by using the --help option.
Tip
You will typically see apt used with the -y option added to the command. This option skips the confirmation prompt, like a popup confirmation you would see in a GUI, for the actions you are taking to speed up the process.
$ apt <action argument> -y
Recall that APT, like all system-wide package managers, must have control over your machine to download, install and configure the packages you need. Because it operates on packages stored above the /home/<username> directory (closer to the root dir) it is considered outside of the user space and requires the use of admin privileges:
$ sudo apt <action argument> -y
The sudo command is the equivalent of opening the PowerShell Terminal in admin mode. It is an acronym for Substitute User to DO the command to the right of it. When used without specifying which user to substitute it will default to running the command to the right as the root user – a special super user account type.
Fun Fact
SUDO is often referred to as super user do because of how often it is used to run commands as root. Most people pronounce it soo-doo or soo-doh.
The first time you use sudo per Shell session you will be prompted for the admin password of your account (launchcode in our case). In simple terms a Shell session is one independent instance of a Shell like Bash. In other words, if you were to open a Terminal and then open another one you would have two active Shell sessions.
Once you have authenticated you will not have to re-authenticate unless you close the Shell (ending the session) or you open a new Shell in a different Terminal window (a new session). You can liken this behavior to how PowerShell requires you to right-click and open as an admin for each Shell session that requires elevated privileges.
Any time you are going to use apt you should begin by updating the metadata in the repository sources. An apt update will download information about installed packages (like pending upgrades) as well as refresh the package source lists. The latter half of the update ensures that when you search and install packages you are always getting the latest additions and versions from your package source repositories.
Below you can see the most ubiquitous apt command in use:
$ sudo apt update
# information about repository source updates
Note
Updating the repository sources only updates the metadata about packages. The actual installed packages can be upgraded to the latest version using the apt upgrade command.
After you have updated you can search for and install package tools on your machine. The search argument can be used to scan the source repositories for a package. It accepts a search term as a sub-argument which it will use to search the title and descriptions of all the available packages within your group of sources.
# always run apt update before searching or installing!
$ sudo apt search <search term>
If the search results contains your package you can install it using the install argument. The sub-argument is the exact package name of the tool you want to install. The installation prompts (like confirmation dialog boxes in a GUI) can be automatically accepted using the -y option:
$ sudo apt install <package name> -y
Let’s practice by searching for the amusing little tool called Cow Say. First let’s search for the package by its name, cowsay. This package is available within the default set of source repositories and should show up as the first result:
$ sudo apt update
# searching doesn't require elevated privileges
$ apt search cowsay
Sorting... Done
Full Text Search... Done
cowsay/focal,focal 3.03+dfsg2-7 all
configurable talking cow
cowsay-off/focal,focal 3.03+dfsg2-7 all
configurable talking cow (offensive cows)
presentty/focal,focal 0.2.1-1.1 all
Console-based presentation software
xcowsay/focal 1.5-1 amd64
Graphical configurable talking cow
# you can also search for "talking cow" which will match the description
$ apt search talking cow
The package that we want is the first one, cowsay. Notice that the search will check both the package name and description.
Let’s install it using the exact package name, cowsay:
# installing controls your machine and requires sudo
$ sudo apt install cowsay -y
In the command output you can see that apt downloads, unpacks and installs the package automatically . You can now try out the newly installed tool!
Use the command program cowsay and enter a message as its arguments:
$ cowsay Hello World!
Note
It is okay to leave cowsay installed. But if you would like to remove it you can use apt to cleanly uninstall it:
$ sudo apt remove cowsay -y
The default list of package repositories provides access to a large collection of open-source tools from package hosts trusted by the open source community. But in many cases you will need to install additional sources to download packages from. Additional sources can range from private repositories hosted by a company, for internal use, to independently-hosted repositories like the Microsoft packages repository.
These custom repositories often require both the repository and a signing key to be installed. Anyone is able to host a repository of packages. This is why it is important to only install source repositories, and packages from those repositories, from trusted sources.
As an additional security measure, trusted repositories include a signing key to check that downloaded packages are authentic (from a trusted source) before being installed.
Note
The topics of Public Key Infrastructure (PKI), which includes signing keys, and custom repositories extends outside the scope of this course. You can read more about how these work in this repository article and this repository signing key article. Both of these articles offer an overview of the mechanisms involved from a relatively high level.
Let’s see what this process looks like using the dotnet CLI installation as an example.
Tip
Like other 3rd party tool installations you can find the instructions on the package maintainer’s site. For example, we will be following the instructions from this Microsoft installation article.
The first step is to install the official Microsoft package repository. The installation includes both the repository and the signing key. This is a one-time process and future installations of Microsoft tools will be available and trusted automatically:
# install the repository source package (includes the repo and signing key)
$ sudo wget https://packages.microsoft.com/config/ubuntu/18.04/packages-microsoft-prod.deb -O packages-microsoft-prod.deb
# unpack and install the repository and trust the signing key
$ sudo dpkg -i packages-microsoft-prod.deb
Microsoft only serves their packages over secure connections (HTTPS). We will need to install a utility called apt-transport-https which, as the name implies, is used to download over HTTPS:
# always update before other commands
$ sudo apt update
$ sudo apt install apt-transport-https -y
Finally with the repository, signing key, and HTTPS tooling installed we can install the dotnet package we were after. We will install the .NET Core SDK which includes both the SDK (standard library, compiler and runtime) as well as the dotnet CLI tool itself:
$ sudo apt update
$ sudo apt install dotnet-sdk-3.1 -y
From the output you can see all of the work that apt does automatically. Imagine doing all of that downloading, unpacking and configuration manually!
You can confirm the installation was successful by viewing the --help output of dotnet. Viewing the help output of a command program is an easy way to get acquainted with it right from the command-line.
$ dotnet --help
Tip
We will work with the dotnet CLI extensively in later lessons. But feel free to poke around with it in the mean time.