pacman

pacman manages installed package records and configured Arch repositories. The local database records installed versions, reasons, files, and ownership; sync databases describe repository packages. Keep those views coherent by refreshing and upgrading in one transaction.

Inspect the Local Database #

Use -Q for installed-package queries:

pacman -Qs '^bash$'
pacman -Qi bash
pacman -Ql bash
pacman -Qo /usr/bin/pacman
pacman -Qk

-Ql lists files supplied by an installed package, -Qo finds the owner of an existing path, and -Qk checks tracked files. pacman -F instead searches the repository file database; populate it first with sudo pacman -Fy.

Package installation reasons affect orphan detection. Inspect or change one deliberately:

pacman -Qi package-name
sudo pacman -D --asexplicit package-name
sudo pacman -D --asdeps package-name

Synchronize and Upgrade Safely #

Search and inspect configured repositories with -Ss and -Si. A normal system update is:

sudo pacman -Syu

-y refreshes sync databases and -u upgrades the installed system against that same repository state. Do not perform partial upgrades such as pacman -Sy package-name: refreshed metadata can require dependencies newer than the installed system. Read Arch news and resolve configuration-file instructions before confirming a large transaction.

Install a repository package with sudo pacman -S package-name. Install a locally built or cached archive with sudo pacman -U file.pkg.tar.zst; pacman still resolves needed dependencies from configured repositories.

Remove Packages and Orphans Deliberately #

pacman -R package-name removes the target. -Rs also removes dependencies made unneeded by that target; -Rns additionally removes retained backup files. Review the proposed removal list before accepting it, because recursive removal can remove dependency packages that another local workflow still expects even when pacman’s dependency graph no longer requires them.

List potential orphans before removing them:

pacman -Qdt
pacman -Qtdq

Only remove names after reviewing the list. An empty pacman -Qtdq result is not an error to work around with an unguarded command substitution.

Preserve Recovery Options #

The default cache directory is /var/cache/pacman/pkg. Retain recent versions; paccache from pacman-contrib can prune older entries while keeping a selected count. A controlled downgrade uses a compatible cached archive:

sudo pacman -U /var/cache/pacman/pkg/package-old.pkg.tar.zst

Downgrading a library may require matching dependent packages. Inspect dependency constraints and plan a coherent transaction rather than replacing files under /usr, which bypasses pacman’s database, hooks, and ownership model. For interrupted or damaged installations, consult /var/log/pacman.log, reinstall affected packages with pacman, and restore files from a verified backup where necessary.

Keep Signature Verification Enabled #

Repository and package signatures protect the supply chain. Fix expired, missing, or revoked trust through archlinux-keyring, pacman-key, system time, and documented mirror configuration; do not disable signature checks to complete an update. Signature errors are evidence that must be understood before packages are installed.