Debian Repository Format
This document is a work in progress that documents the structure of the official Debian repository and the format that is officially understood by clients. It's purpose is to define how a Debian repository should be structured, and how clients should interpret this.
Contents
Overview
Debian package archives are primarily used to store and retrieve packages automatically.
Most if not all package managers use libapt for package retrieval from external media and the internet.
The sources.list man page specifies this package source format:
deb uri distribution [component1] [component2] [...]
and gives an example:
deb http://ftp.debian.org/debian squeeze main contrib non-free
Here deb specifies that this is source for binary packages, _deb-src_ is for source packages.
An archive can have either source packages or binary packages or both but they have to be specified separately to apt.
The uri, in this case http://ftp.debian.org/debian/ specifies the root of the archive. Traditionally Debian archives are in the debian/ directory on the server but can be anywhere else.
The distribution part (squeeze in this case) specifies a subdirectory in $ARCHIVE_ROOT/dists. It can contain additional slashes to specify subdirectories nested deeper, eg. squeeze/updates. distribution typically corresponds to Suite or Codename specified in the Release files. FIXME is this enforced anyhow?
To download packages from a repository apt would download a ?InRelease or Release file from the $ARCHIVE_ROOT/dists/$DISTRIBUTION directory.
?InRelease files are signed in-line while Release files should have an accompanying Release.gpg file.
The Release file lists the index files for the distribution and their hashes (the index file listed are relative to Release file location).
To download index of the main component apt would scan the Release file for hashes of files in the main directory. eg. http://ftp.cz.debian.org/debian/dists/testing/main/binary-i386/Packages.bz2 which would be listed in http://ftp.cz.debian.org/debian/dists/testing/main/Release as binary-i386/Packages.bz2
Binary package indices are in binary-$arch subdirectory of the component directories. Source indices are in source subdirectory.
Package indices list specific source or binary packages relative to the archive root.
Traditionally binary and source packages are kept in the pool subdirectory of the archive root. The Packages and Sources indices can list any path relative to archive root, however. It is suggested that packages are palced in a subdirectory of archive root other than dists rather than directly in archive root. Placing packages directly in the archive root is not tested and some tools may fail to index or retrieva packages placed there.
"Release" files
The file "dists/$DIST/InRelease" shall contain meta-information about the distribution and checksums for the indices, possibly signed with a GPG cleansign signature (for example created by "gpg -a -s --clearsign"). For older clients there can also be a "dists/$DIST/Release" file without any signature and the file "dists/$DIST/Release.gpg" with a detached GPG signature of the "Release" file, compatible with the format used by the GPG options "-a -b -s".
The following fields have a well defined meaning:
- These fields are optional. They may be displayed to the user by package management tool or used for pinning. It is suggested that any repository published for other users to use fills meaningful information in these fields so that the user can tell apart different repositories.
- Description
- Origin
- Label
- Suite
- These fields determine layout of the repository and should contain something meaningful to the user.
- Codename
- Components
- Architectures
- These optional fields are purely functional and used mostly internally by packaging tools.
Servers shall provide the ?InRelease file, and might provide a Release files and its signed counterparts with at least the following keys:
- SHA256
- Suite and/or Codename
- Architectures
- Components
Still having a unsigned Release file and MD5Sum is currently highly recommended.
Clients may accept missing Release files, and Release files without the fields required for servers. They might reject Release files that do not contain at least one of the fields defined herein.
Architectures
Whitespace separated unique single words identifying Debian machine architectures as described in Architecture specification strings, Section 11.1. Clients should ignore Architectures they do not know about.
Origin
Optional field indicating the origin of the repository.
Label
Optional field including some kind of label.
Suite
The Suite field may describe the suite. In Debian, this shall be one of oldstable, stable, testing, unstable, or experimental; with optional suffixes separated by "-" (such as "stable-updates").
Codename
The Suite field shall describe the codename of the release. This is mostly a free-form string used to give a name to a release. (TODO: it's not really free-form, document the requirements).
Date,Valid-Until
The Date field shall specify the time at which the Release file was created. The Valid-Until field may specify at which time the Release file should be considered expired by the client. Client behaviour on expired Release files is unspecified.
Components
A whitespace separated list of areas.
Example:
- Components: main contrib non-free
MD5Sum, SHA1, SHA256
These fields are used for two purposes:
- describe what package index files are present
- when release signature is available it certifies that listed index files and files referenced by those index files are genuine
Those fields shall be multi-line fields containing multiple lines of whitespace separated data. Each line shall contain
- The checksum of the file in the format corresponding to the field
The size of the file (integer >= 0)
- The filename relative to the directory of the Release file
Each datum must be seperated by one or more whitespace characters.
Server requirements:
- The checksum and sizes shall match the actual existing files. When indexes are compressed checksum data should be provided for uncompressed files as well, even if not present on the server. Previously it was possible to supply a compressed file and checksum of uncompressed file only but this is no longer supported. Clients supporting multiple compression methods cannot infer the compressed file name when the release file contains uncompressed file checksum.
Client behaviour:
- Any file should be checked at least once, either in compressed or uncompressed form, depending on which data is available. If a file has no associated data, the client shall inform the user about this under possibly dangerous situations (such as installing a package from that repository). If a file does not match the data specified in the release file, the client shall not use any information from that file, inform the user, and might use old information (such as the previous locally kept information) instead.
NotAutomatic and ButAutomaticUpgrades
The ?NotAutomatic and ?ButAutomaticUpgrades fields are boolean fields instructing the package manager. They may contain the values "yes" and "no".
If "?NotAutomatic: yes" is specified, the client should prevent installation of packages from this repository unless explicitely requested (APT will assign priority 1 to that repository).
If "?ButAutomaticUpgrades: yes" is specified in addition to "?NotAutomatic: yes", the client should cause upgrades to packages from that repository to be installed automatically (APT will assign priority 100 to that repository).
If both are either missing or set to "No", the repository should behave like any other repository (APT will assign either priority 500 or 990 by default, depending on whether the release is it's target release).
Other combinations are undefined.
"Packages" Indices
The files dists/$DIST/$COMP/binary-$ARCH/Packages are called Binary Packages Indices. They consist of multiple paragraphs, where each paragraph has the format defined in Policy 5.3 (Binary package control files -- DEBIAN/control), and the additional fields defined in this section.
Note that the control file of .deb files may contain additional fields not yet documented by policy or not yet documented by policy which then might also be found in this file.
Filename
The Filename field shall list the path of the package archive relative to the base directory of the repository.
Example:
- Filename: pool/main/a/apt/apt_0.9.3_amd64.deb
Required: yes
Size
The size field shall give the size of the package file, in bytes.
Example:
- Size: 1158196
Required: yes
MD5sum, SHA1, SHA256
Checksums for the package. They shall be represented in hexadecimal notation. The MD5sum and SHA1 fields should be considered deprecated, but should still be provided.
Examples:
MD5sum: 2519c8c1afd27e70cf4ac10a5fa46e32 SHA1: 646eda5b6d51190181c15f5537428161f6f04c1d SHA256: 3183eff291d1e9d905e78a6b467bbfb90b20fc2808d50b5e91bf55158b4c18be
Server requirements: SHA256 shall be available Client requirements: Shall accept files without any such fields, should warn
- if those fields are missing and a package is used.
Description-md5
An MD5 sum of the English description. This will be used to lookup the descriptions in the Translation indices. If this field is not defined, the MD5 sum shall be calculated from the Description field.
Server requirements:
- Either Description or Description-md5 shall be specified.
Client requirements:
- If neither Description, nor Description-MD5 is defined, the result shall be the same as if an empty description was specified for all languages. If Description-md5 is defined, the long description shall be looked up via translation indices if requested.
Example:
- Description-md5: 9fb97a88cb7383934ef963352b53b4a7
Description
The Description field shall contain the complete package description, if Description-md5 is not defined; or only the short description of the package, if Description-md5 is defined.
"Sources" Indices
The files dists/$DIST/$COMP/source/Sources are called Sources indices. They consist of multiple paragraphs, where each paragraph has the format defined in Policy 5.5 (5.4 Debian source control files -- .dsc), with the following changes and additional fields. The changes are:
- The "Source" field is renamed to "Package"
- A new mandatory field "Directory"
- A new optional field "Priority"
- A new optional field "Section"
(Note that any fields present in .dsc files can end here as well, even if they are not documented by Debian policy, or not yet documented yet).
Directory
The directory field shall list the location of the source package in the repository, relative to the base directory of the repository.
Example:
- Directory: pool/main/a/apt
Priority
Shall contain the value "source".
Example:
- Priority: source
Section
Shall contain the section specified for the source package??
Example:
- Section: admin
"Contents" indices
The files dists/$DIST/$COMP/Contents-$SARCH.gz are so called Contents indices. The variable $SARCH means either a binary architecture or the pseudo-architecture "source" that represents source packages. They are optional indices describing which files can be found in which packages.
Contents indices begin with zero or more lines of free form text followed by a table mapping filenames to one or more packages. The table SHALL have two columns, separated by one or more spaces. The first row of the table SHOULD have the columns "FILE" and "LOCATION", the following rows shall have the following columns:
- A filename relative to the root directory, without leading .
- A list of qualified package names, separated by comma, where a qualified package name has the format "SECTION/NAME". The "SECTION/" part is optional for "Contents-source" indices.
The right column does not have white space characters, whereas a file name may have white space characters. A client should handle this.
Clients should ignore lines they do not understand. This takes care of the header, and also possibly in-between data created by third-party repositories.
indices difference files (diffs)
For each of the indices previously defined, repositories may also provide indices difference files, that contain the differences to previous versions of the index.
If an (uncompressed) index is located at the path $I, then a directory called $I.diff can exist. This directory contains the following files:
- Index
- Compressed Difference files in the format "%Y-%m-%d-%H%M.%S.gz"
.diff/Index files
The index file shall be a file with the following fields:
- SHA1-Current
- SHA1-History
- SHA1-Patches
SHA1-Current
The SHA1 of the current index $I. This is the same one as listed in a SHA1 field of the Release file to make sure it is the right diff file.
SHA1-History and SHA1-Patches
The SHA1-History and SHA1-Patches field are multi-line fields, where each line consists of the following columns, separated by a single space:
- A SHA1 checksum
- A size
- The name of a patch file
For SHA1-History, the SHA1 and the size describe the index to which the patch applies. For SHA1-Patches, the SHA1 and the size refer to the uncompressed patch file.
Example:
SHA1-Current: 8d190506d0c20b20b3cee06956e2061f3c083281 29137603 SHA1-History: a3cc0e588a41662db61e432f8c174a0d29aa4a9b 29086963 2012-05-04-2025.35 SHA1-Patches: 351c97e091e10313eb7e2aeb8a1dd8088726cf20 91134 2012-05-04-2025.35
Each patch applied to the old version of the index file listed in SHA1-History creates a new file that either is the file looked for or some other old version that is also listed in SHA1-History.
DAK currently creates patches to be applied one by one. reprepro creates patches directly resulting in the final file. reprepro also adds a line
X-Patch-Precedence: merged
so clients wishing to optimize for one-by-one applying know that this is not possible.
.diff/%Y-%m-%d-%H%M.%S files
Those files are in a format that is a subset of the "patch --ed" format.
FIXME: Explain
- FIXME
- optional
- optimize index download size for large archives with few changes
"Translation" indices
The directory dists/$DIST/$COMP/i18n/ contains the file index, with a SHA1 field listing the description indices in that directory, in the same format as used for Release files, and one or more description indices.
Each description index has the format Translation-$LANG.bz2, where $LANG is a language code corresponding to a locale.
A Translation index is like a Packages index, but has the following fields only:
Package
Description-md5
Description-$LANG
The Package and Description-md5 fields have the same meaning as for Packages indices. The Description-$LANG field, where $LANG is the same value as that of $LANG in the filename, shall be a description as described in Policy 5.6.13 Description, localized for that language.
The file Translation-en.bz2 contains the English language descriptions, if those are not supplied in the Packages index.
Example:
Package: aspell-ca Description-md5: ac1a5e69d940eb04be1942837e419d62 Description-ca: Diccionari català per aspell Aquest paquet conté tots els fitxers necessaris per afegir suport per l'idioma català pel corrector ortogràfic GNU Aspell. . Va ser recollit per en Joan Moratinos utilitzant dades de diverses fonts.