Packages

linuxfundamentalspart3 linuxfundamentals

On Linux distributions, packages are archives used to share:

  • 📚 Libraries (.a and .so files)
  • ✍️ Documentation (packagename-doc)
  • 📄 Headers (packagename-dev)
  • 🕹️ Applications (binaries)
  • ...

Each operating system has a package management system to install and remove packages. We usually don't directly interact with it, and we use a package management tool instead. They allow us to download packages from package repositories and update them too.

In a nutshell, we often see these combinations:

Package System 🖥️ Package Tool 🛠️ Package format 🗝️
dpkg apt or aptitude .deb
rpm dnf or yum ☠️ .rpm
pacman pacman
  • dpkg is mainly used by Debian-like distributions.
  • rpm is mainly used by Fedora and Red Hat.
  • pacman is mainly used by Arch Linux.

Package Systems And Tools

Usage 🐚: apt is the default package manager on well-known Linux distros such as Debian/Ubuntu.

Example 🔥:

Install, Update, Remove a package

$ sudo apt install aptitude
$ sudo apt update aptitude
$ sudo apt upgrade aptitude
$ sudo apt remove aptitude

Download updates for/upgrade all packages

$ sudo apt update
$ sudo apt upgrade

Update the OS 🧪

$ sudo apt dist-upgrade

Remove unused dependencies

$ sudo apt autoremove
$ sudo apt auto-remove

When installing packages, you are prompted Do you want to continue? [Y/n] (you need to enter Y). You can skip this, using -y.

$ sudo apt install -y aptitude

Configuration files are stored in /etc/apt/:

$ cat /etc/apt/sources.list # repositories
$ ls /etc/apt/apt.conf.d/   # proxy conf etc.

List installed packages:

$ apt list --installed

Usage 🐚: aptitude (which has to be installed) is the same as apt, but there is a graphical interface.

Example 🔥:

$ sudo aptitude # press 'q' to quit

Or, you can use it like apt:

$ sudo aptitude install nano

Usage 🐚: apt uses the lower-level package manager dpkg to install packages. Some developers may directly interact with it.

Example 🔥:

$ sudo dpkg -i xxx.deb

Usage 🐚: snap packages are a modern way to share applications. They contain all dependencies, and support automatic updates. Some cons are their larger size and sometimes there are performance issues.

👉 Find Snap packages here.

Example 🔥:

$ sudo apt update
$ sudo apt install snapd
$ sudo snap install core
$ sudo snap refresh core
$ sudo snap install --classic xxx

Usage 🐚: available on Debian-based distributions. Allow us to switch between multiple versions of the same program.

🛻 c++, cc, nc, php, java...

Example 🔥:

$ sudo update-alternatives --config php

Mirrors

To reduce the time it takes to download packages, multiple mirrors of package repositories are set up, and users should use the nearest ones. A mirror is basically a copy of a package repository.

It could be hosted locally.

apt-mirror

Apt-mirror is a tool used on Linux to create a mirror.

$ sudo apt-get install apt-mirror
$ sudo cat /etc/apt/mirror.list
set base_path    /path/to/mirror
set run_postmirror 0

deb http://deb.nodesource.com/node_10.x/ buster main
clean http://deb.nodesource.com/node_10.x
$ sudo apt-mirror /etc/apt/mirror.list

It will create a folder mirror inside /path/to/mirror with:

  • dists/<codename>/<repository>: contains the metadata
  • pool/<repository>: contains the downloaded packages

Aptly

Aptly is a powerful tool created to simplify the process of creating and maintaining package repositories. It can be used to create mirrors.

$ apt-key adv --keyserver keyserver.ubuntu.com --recv-keys A0546A43624A8331
$ sudo apt-get install aptly
$ sudo cat ~/.aptly.conf     # aptly config show
{
    "rootDir": "/path/to/mirror",
    "downloadConcurrency": 20,
    "architectures": ["amd64"]
}
$ [handle gpg problems]
$ aptly mirror create node20 https://apt.nodesource.com/node_20.x nodistro main
$ aptly mirror update node20

👻 To-do 👻

Stuff that I found, but never read/used yet.

$ apt-file
$ apt-file update
$ apt autoclean
$ wget -qO - xxx.gpg | apt-key add -
  • APT store information about packages in a local database for offline use.
$ apt-cache search <name>
$ apt-cache show <package_name>