Pacman

Pacman is Arch Linux's package manager (also used by Arch derivatives like Manjaro and EndeavourOS). Unlike Debian/Ubuntu or Fedora/RHEL, Arch doesn't separate a low-level and high-level tool the way dpkg/apt or rpm/dnf do - pacman handles both package installation and dependency resolution itself.

Everyday commands

sudo pacman -Syu              # sync repo databases AND upgrade everything
sudo pacman -S nginx          # install a package
sudo pacman -R nginx          # remove a package, keep its config/dependencies
sudo pacman -Rs nginx         # remove a package AND dependencies no longer needed
pacman -Ss "web server"       # search the repositories
pacman -Qs nginx              # search installed packages
pacman -Qi nginx              # detailed info about an installed package
pacman -Ql nginx              # list every file the package installed

Pacman's flags follow a consistent pattern once memorized: the capital letter (S sync, R remove, Q query) picks the operation, lowercase letters modify it (y refresh databases, u upgrade, s search or include dependencies depending on context).

Always run -Syu together, as one command, never -Sy followed by a separate -S <package> later - updating the package database without immediately upgrading (called a "partial upgrade") is an unsupported state on Arch and a well-known way to break dependency resolution.

Configuration

/etc/pacman.conf

Defines enabled repositories ([core], [extra], [multilib] for 32-bit compatibility packages) and general options like which mirrors to use, configured separately in /etc/pacman.d/mirrorlist.

The rolling-release model

Arch has no versioned releases the way Ubuntu or Fedora do - every pacman -Syu pulls whatever the current upstream package versions are, continuously. This means the latest software, sooner, but also more exposure to occasional breaking changes that a fixed-release distro would have caught during a dedicated release cycle.

Because of this, checking the Arch news feed (archlinux.org/news, or informant as a pacman hook that surfaces it automatically) before a big update is a standard practice - some upgrades require manual intervention (a config file format change, a mid-upgrade package split) that pacman itself can't handle automatically, and skipping the news is the most common way an Arch system update goes wrong.

The AUR

The Arch User Repository (AUR) hosts community-submitted build scripts (PKGBUILD files) for software not packaged in Arch's official repositories - not precompiled binaries, but recipes that pacman itself cannot install directly. Pacman has no built-in AUR support; installing from it means either building manually:

git clone https://aur.archlinux.org/some-package.git
cd some-package
makepkg -si

or using an AUR helper - a third-party wrapper that automates this, most commonly yay or paru:

yay -S some-aur-package

AUR packages are user-submitted and not vetted the way official repository packages are - read a PKGBUILD before trusting it with makepkg -si, since it runs arbitrary shell code as part of the build.

See Building From Source for what makepkg is actually automating underneath.