NAME

alpm-db - a database format for describing the state of packages on an Arch Linux Package Management (ALPM) based system.

DESCRIPTION

The databases on ALPM based systems are represented by a directory structure that contains metadata files. The contents of such a database describes the state of all installed packages. Here, ALPM-MTREE, alpm-db-desc and alpm-db-files files provide metadata on specific package versions currently installed.

Entries for databases are created from alpm-package files using package management software such as pacman. Package management software relies on alpm-db structures for the purpose of search, dependency resolution and system management.

The alpm-db format exists in multiple versions. The information in this document is for version 9, which is the current version and has been introduced with the release of pacman 4.2.0 on 2014-12-19.

The contents of the system database depend on the number of unique packages it describes. Each package can only appear once, in a single version.

Metadata

Metadata of a package is kept in a top-level directory, that is named after the package and its specific version. The name follows this schema:

An alpm-package-name directly followed by a - sign, directly followed by an alpm-package-version (in the full or full with epoch form), e.g.:

example-package-1.0.0-1
example-package-1:1.0.0-1

In each of these directories, one ALPM-MTREE, one alpm-db-desc and one alpm-db-files file are kept to describe a package, e.g.:

.
└── example-package-1.0.0-1
    ├── desc
    ├── files
    └── mtree

Schema version

The current schema version of the system database is encoded in the top-level version file ALPM_DB_VERSION. This ASCII text file contains a single line with a numeric version string, e.g.:

When changes to the format of the system database are necessary, they are indicated by incrementing the version string intended for the version file.

Dedicated tools such as pacman-db-upgrade are used to upgrade the contents of the system database (e.g. metadata files, directory structure) and eventually update the version in ALPM_DB_VERSION.

Creation

The data in an alpm-db is derived from alpm-package files and created using package management software such as pacman. For the alpm-db-desc entries, the package's PKGINFO data, as well as the properties of the package file are used. The alpm-repo-files file is directly derived from the package file's list of data files. The ALPM-MTREE file is a copy of the package's ALPM-MTREE file.

              alpm-db -----------.
              /  |  \             \
             /   |   \             \
alpm-db-files    |    alpm-db-desc  |
    |            |         |        |
    |         ALPM-MTREE   |        |
 data files      |         |        |
       \         |       PKGINFO   /
        \        |     /          /
         \       |    /          /
          alpm-package-----------

EXAMPLES

Installing a package on a system

Assuming an empty system, the installation of a package example-package in version 1.0.0-1 leads to the following addition in the alpm-db:

.
└── example-package-1.0.0-1
    ├── desc
    ├── files
    └── mtree

Upgrading an existing package on a system

Extending on the previous example on installing a package on a system, the upgrade of a package example-package to version 1.1.0-1 leads to the following change in the alpm-db:

.
└── example-package-1.1.0-1
    ├── desc
    ├── files
    └── mtree

ALPM