pacman and pkgfile
pacman the package management system
A simple library-based package manager.
In the October meeting, we discussed some of the most popular usages of
pacman and pkgfile, I intend to go into a bit more detail in this document.
Introduction
pacman is a utility which manages software packages in Linux. It uses simple compressed files as a package format, and maintains a text-based package database (more of a hierarchy), just in case some hand tweaking is necessary.
pacman does not strive to "do everything." It will add, remove and upgrade packages in the system, and it will allow you to query the package database for installed packages, files and owners. It also attempts to handle dependencies automatically and can download packages from a remote server.
History:
Version 2.0 of pacman introduced the ability to sync packages (the --sync option) with a master server through the use of package databases. Prior to this, packages would have to be installed manually using the --add and --upgrade operations.
Version 3.0 was the switch to a two-part pacman?—?a back-end named libalpm (library for Arch Linux Package Management) and the familiar pacman front-end. Speed in many cases was improved, along with dependency and conflict resolution being able to handle a much wider variety of cases. The switch to a library-based program should also make it easier in the future to develop alternative front ends.
Version 4.0 added package signing and verification capabilities to the entire makepkg/repo-add/pacman toolchain via GnuPG and GPGME.
Version 5.0 added support for pre/post-transaction hooks and sync database file list operations.
[From the manfile]:
pacman DESCRIPTION
Pacman is a package management utility that tracks installed packages
on a Linux system. It features dependency support, package groups,
install and uninstall scripts, and the ability to sync your local
machine with a remote repository to automatically upgrade packages.
Pacman packages are a zipped tar format.
Since version 3.0.0, pacman has been the front-end to libalpm(3), the
“Arch Linux Package Management” library. This library allows
alternative front-ends to be written (for instance, a GUI front-end).
Invoking pacman involves specifying an operation with any potential
options and targets to operate on. A target is usually a package name,
file name, URL, or a search string. Targets can be provided as command
line arguments. Additionally, if stdin is not from a terminal and a
single hyphen (-) is passed as an argument, targets will be read from
stdin.
The popular commands we discussed in the meeting:
for pacman
pacman -Syu #to update the entire system, (all packages)
Explainations:
-S, --sync
Synchronize packages. Packages are installed directly from the
remote repositories, including all dependencies required to run the
packages. For example, pacman -S qt will download and install qt
and all the packages it depends on. If a package name exists in
more than one repository, the repository can be explicitly
specified to clarify the package to install: pacman -S testing/qt.
You can also specify version requirements: pacman -S "bash>=3.2".
Quotes are needed, otherwise the shell interprets ">" as
redirection to a file.
In addition to packages, groups can be specified as well. For
example, if gnome is a defined package group, then pacman -S gnome
will provide a prompt allowing you to select which packages to
install from a numbered list. The package selection is specified
using a space- and/or comma-separated list of package numbers.
Sequential packages may be selected by specifying the first and
last package numbers separated by a hyphen (-). Excluding packages
is achieved by prefixing a number or range of numbers with a caret
(^).
Packages that provide other packages are also handled. For example,
pacman -S foo will first look for a foo package. If foo is not
found, packages that provide the same functionality as foo will be
searched for. If any package is found, it will be installed. A
selection prompt is provided if multiple packages providing foo are
found.
You can also use pacman -Su to upgrade all packages that are
out-of-date. See Sync Options below. When upgrading, pacman
performs version comparison to determine which packages need
upgrading. This behavior operates as follows:
Alphanumeric:
1.0a < 1.0b < 1.0beta < 1.0p < 1.0pre < 1.0rc < 1.0 < 1.0.a < 1.0.1
Numeric:
1 < 1.0 < 1.1 < 1.1.1 < 1.2 < 2.0 < 3.0.0
Additionally, version strings can have an epoch value defined that
will overrule any version comparison, unless the epoch values are
equal. This is specified in an epoch:version-rel format. For
example, 2:1.0-1 is always greater than 1:3.6-1.
-y, --refresh
Download a fresh copy of the master package database from the
server(s) defined in pacman.conf(5). This should typically be used
each time you use --sysupgrade or -u. Passing two --refresh or -y
flags will force a refresh of all package databases, even if they
appear to be up-to-date.
-u, --sysupgrade
Upgrades all packages that are out-of-date. Each
currently-installed package will be examined and upgraded if a
newer package exists. A report of all packages to upgrade will be
presented, and the operation will not proceed without user
confirmation. Dependencies are automatically resolved at this level
and will be installed/upgraded if necessary.
Pass this option twice to enable package downgrades; in this case,
pacman will select sync packages whose versions do not match with
the local versions. This can be useful when the user switches from
a testing repository to a stable one.
Additional targets can also be specified manually, so that -Su foo
will do a system upgrade and install/upgrade the "foo" package in
the same operation.
pacman -S # To install packages (listed packages or suites of packages)
(package names separated by spaces) … but you can also
use -Syu to install package(s) and upgrade everything as
well.
pacman -U # To install from file. (You can cd to directory with downloaded
and use this command to install the package)
-U, --upgrade
Upgrade or add package(s) to the system and install the required
dependencies from sync repositories. Either a URL or file path can
be specified. This is a “remove-then-add” process. See Upgrade
Options below; also see Handling Config Files for an explanation on
how pacman takes care of configuration files.
pacman -Ss # To search for a package
-s, --search <regexp>
Search each locally-installed package for names or descriptions
that match regexp. When including multiple search terms, only
packages with descriptions matching ALL of those terms are
returned.
pkfile DESCRIPTION
pkgfile searches the .files metadata created by repo-add(8) to retrieve
file information about packages. By default, the provided target is
considered to be a filename and pkgfile will return the package(s)
which contain this file. The repos which pkgfile searches is determined
by those enabled in /etc/pacman.conf.
The popular usages of pkgfile:
pkgfile <file-name-here> # Search for a command or package that may be part of a package a suite of packages, (such as ifconfig)
Examples:
$ pkgfile ifconfig
core/net-tools
$ pkgfile iwconfig
core/wireless_tools
$ pkgfile convert
extra/imagemagick
Of course, if the command is the same name of one single package, here is what you get:
$ pkgfile nmap
extra/nmap
There are several man pages available for the programs, utilities, and configuration files dealing with pacman.
Although the package manager itself is quite simple, many scripts have been developed that help automate building and installing packages. These are used extensively in Arch Linux. Most of these utilities are available in the Arch Linux projects code browser.
Other Utilities
Utilities available:
-
abs - ABS (Arch Build System), scripts to download & use the Arch Linux PKGBUILD tree
-
dbscripts - scripts used by Arch Linux to manage the main package repositories
-
devtools - tools to assist in packaging and dependency checking
-
namcap - a package analysis utility written in python
srcpac - a bash build-from-source pacman wrapper
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Here is a list of Linux Distributions that use pacman as their package
management system:
Mailing Lists
There is a mailing list devoted to pacman development, hosted by Arch Linux. Subscribe or view the archives.