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diff --git a/doc/files.dbk b/doc/files.dbk new file mode 100644 index 0000000..95e6257 --- /dev/null +++ b/doc/files.dbk @@ -0,0 +1,393 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" + "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [ +<!ENTITY % aptent SYSTEM "apt.ent"> %aptent; +<!ENTITY % aptverbatiment SYSTEM "apt-verbatim.ent"> %aptverbatiment; +<!ENTITY % aptvendor SYSTEM "apt-vendor.ent"> %aptvendor; +]> + +<book lang="en"> + +<title>APT Files</title> + +<bookinfo> + +<authorgroup> + <author> + <personname>Jason Gunthorpe</personname><email>jgg@debian.org</email> + </author> +</authorgroup> + +<releaseinfo>Version &apt-product-version;</releaseinfo> + +<abstract> +<para> +This document describes the complete implementation and format of the installed +APT directory structure. It also serves as guide to how APT views the Debian +archive. +</para> +</abstract> + +<copyright><year>1998-1999</year><holder>Jason Gunthorpe</holder></copyright> + +<legalnotice> +<title>License Notice</title> +<para> +"APT" and this document are free software; you can redistribute them and/or +modify them under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2 of the License, or (at your +option) any later version. +</para> +<para> +For more details, on Debian systems, see the file +/usr/share/common-licenses/GPL for the full license. +</para> +</legalnotice> + +</bookinfo> + +<chapter id="ch1"><title>Introduction</title> + +<section id="s1.1"><title>General</title> +<para> +This document serves two purposes. The first is to document the installed +directory structure and the format and purpose of each file. The second +purpose is to document how APT views the Debian archive and deals with multiple +package files. +</para> +<para> +The var directory structure is as follows: +</para> +<screen> + /var/lib/apt/ + lists/ + partial/ + periodic/ + extended_states + cdroms.list + /var/cache/apt/ + archives/ + partial/ + pkgcache.bin + srcpkgcache.bin + /etc/apt/ + sources.list.d/ + apt.conf.d/ + preferences.d/ + trusted.gpg.d/ + sources.list + apt.conf + apt_preferences + trusted.gpg + /usr/lib/apt/ + methods/ + bzip2 + cdrom + copy + file + ftp + gpgv + gzip + http + https + lzma + rred + rsh + ssh +</screen> +<para> +As is specified in the FHS 2.1 /var/lib/apt is used for application data that +is not expected to be user modified. /var/cache/apt is used for regeneratable +data and is where the package cache and downloaded .debs go. /etc/apt is the +place where configuration should happen and /usr/lib/apt is the place where the +apt and other packages can place binaries which can be used by the acquire +system of APT. +</para> +</section> + +</chapter> + +<chapter id="ch2"><title>Files</title> + +<section id="s2.1"><title>Files and fragment directories in /etc/apt</title> +<para> +All files in /etc/apt are used to modify specific aspects of APT. To enable +other packages to ship needed configuration herself all these files have a +fragment directory packages can place their files in instead of mangling with +the main files. The main files are therefore considered to be only used by the +user and not by a package. The documentation omits this directories most of +the time to be easier readable, so every time the documentation includes a +reference to a main file it really means the file or the fragment directories. +</para> +</section> + +<section id="s2.2"><title>Distribution Source list (sources.list)</title> +<para> +The distribution source list is used to locate archives of the debian +distribution. It is designed to support any number of active sources and to +support a mix of source media. The file lists one source per line, with the +fastest source listed first. The format of each line is: +</para> +<para> +<replaceable>type uri args</replaceable> +</para> +<para> +The first item, <replaceable>type</replaceable>, indicates the format for the +remainder of the line. It is designed to indicate the structure of the +distribution the line is talking about. Currently the only defined values are +<emphasis>deb</emphasis> and <emphasis>deb-src</emphasis> which indicate a +standard debian (source) archive with a dists directory. More about these +types and the URI specification can be found in the sources.list manpage. +</para> + +<section id="s2.2.1"><title>Hashing the URI</title> +<para> +All permanent information acquired from any of the sources is stored in the +lists directory. Thus, there must be a way to relate the filename in the lists +directory to a line in the sourcelist. To simplify things this is done by +quoting the URI and treating _'s as quoteable characters and converting / +to _. The URI spec says this is done by converting a sensitive character +into %xx where xx is the hexadecimal representation from the ASCII character +set. Examples: +</para> +<screen> +http://www.debian.org/archive/dists/stable/binary-i386/Packages +/var/lib/apt/lists/www.debian.org_archive_dists_stable_binary-i386_Packages + +cdrom:Debian 1.3/debian/Packages +/var/lib/apt/info/Debian%201.3_debian_Packages +</screen> +<para> +The other alternative that was considered was to use a deep directory structure +but this poses two problems, it makes it very difficult to prune directories +back when sources are no longer used and complicates the handling of the +partial directory. This gives a very simple way to deal with all of the +situations that can arise. Also note that the same rules described in the +<emphasis>Archive Directory</emphasis> section regarding the partial sub dir +apply here as well. +</para> +</section> + +</section> + +<section id="s2.3"><title>Extended States File (extended_states)</title> +<para> +The extended_states file serves the same purpose as the normal dpkg status +file (/var/lib/dpkg/status) except that it stores information unique to +apt. This includes currently only the autoflag but is open to store more +unique data that come up over time. It duplicates nothing from the normal +dpkg status file. Please see other APT documentation for a discussion of +the exact internal behavior of these fields. The Package and the Architecture +field are placed directly before the new fields to indicate which package +they apply to. The new fields are as follows: +</para> +<variablelist> +<varlistentry> +<term>Auto-Installed</term> +<listitem> +<para> +The Auto flag can be 1 (Yes) or 0 (No) and controls whether the package was +automatically installed to satisfy a dependency or if the user requested the +installation +</para> +</listitem> +</varlistentry> +</variablelist> +</section> + +<section id="s2.4"><title>Binary Package Cache (srcpkgcache.bin and pkgcache.bin)</title> +<para> +Please see cache.sgml for a complete description of what this file +is. The cache file is updated whenever the Packages or Release files of the lists +directory or the dpkg status file changes. If the cache is erased, corrupted or of a non-matching +version it will be automatically rebuilt by all of the tools that need +it. <emphasis>srcpkgcache.bin</emphasis> contains a cache of all of the +package, release files in the source list. In comparison to <emphasis>pkgcache.bin</emphasis>, it does not include the /var/lib/dpkg/status file. This allows regeneration of the cache +when the status files change to use a prebuilt version for greater speed. +</para> +</section> + +<section id="s2.5"><title>Downloads Directory (archives)</title> +<para> +The archives directory is where all downloaded .deb archives go. When the file +transfer is initiated the deb is placed in partial. Once the file is fully +downloaded and its MD5 hash and size are verified it is moved from partial +into archives/. Any files found in archives/ can be assumed to be verified. +</para> +<para> +No directory structure is transferred from the receiving site and all .deb file +names conform to debian conventions. No short (msdos) filename should be +placed in archives. If the need arises .debs should be unpacked, scanned and +renamed to their correct internal names. This is mostly to prevent file name +conflicts but other programs may depend on this if convenient. A conforming +.deb is one of the form, name_version_arch.deb. Our archive scripts do not +handle epochs, but they are necessary and should be re-inserted. If necessary +_'s and :'s in the fields should be quoted using the % convention. It must be +possible to extract all 3 fields by examining the file name. Downloaded .debs +must be found in one of the package lists with an exact name + version match.. +</para> +</section> + +<section id="s2.6"><title>The Methods Directory (/usr/lib/apt/methods)</title> +<para> +The Methods directory is more fully described in the APT Methods interface +document. +</para> +</section> + +<section id="s2.7"><title>The Configuration File (/etc/apt/apt.conf)</title> +<para> +The configuration file (and the associated fragments directory +/etc/apt/apt.conf.d/) is described in the apt.conf manpage. +</para> +</section> + +<section id="s2.8"><title>The trusted.gpg File (/etc/apt/trusted.gpg)</title> +<para> +The trusted.gpg file (and the files in the associated fragments directory +/etc/apt/trusted.gpg.d/) is a binary file including the keyring used by apt to +validate that the information (e.g. the Release file) it downloads are really +from the distributor it clams to be and is unmodified and is therefore the last +step in the chain of trust between the archive and the end user. This security +system is described in the apt-secure manpage. +</para> +</section> + +<section id="s2.9"><title>The Release File</title> +<para> +This file plays an important role in how APT presents the archive to the +user. Its main purpose is to present a descriptive name for the source of +each version of each package. It also is used to detect when new versions +of debian are released. It augments the package file it is associated with +by providing meta information about the entire archive which the Packages +file describes. +</para> +<para> +The full name of the distribution for presentation to the user is formed as +'label version archive', with a possible extended name being 'label version +archive component'. +</para> +<para> +The file is formed as the package file (RFC-822) with the following tags +defined: +</para> +<variablelist> +<varlistentry> +<term>Archive</term> +<listitem> +<para> +This is the common name we give our archives, such as +<emphasis>stable</emphasis> or <emphasis>unstable</emphasis>. +</para> +</listitem> +</varlistentry> +<varlistentry> +<term>Component</term> +<listitem> +<para> +Refers to the sub-component of the archive, <emphasis>main</emphasis>, +<emphasis>contrib</emphasis> etc. Component may be omitted if there are no +components for this archive. +</para> +</listitem> +</varlistentry> +<varlistentry> +<term>Version</term> +<listitem> +<para> +This is a version string with the same properties as in the Packages file. It +represents the release level of the archive. +</para> +</listitem> +</varlistentry> +<varlistentry> +<term>Origin</term> +<listitem> +<para> +This specifies who is providing this archive. In the case of Debian the string +will read 'Debian'. Other providers may use their own string +</para> +</listitem> +</varlistentry> +<varlistentry> +<term>Label</term> +<listitem> +<para> +This carries the encompassing name of the distribution. For Debian proper this +field reads 'Debian'. For derived distributions it should contain their proper +name. +</para> +</listitem> +</varlistentry> +<varlistentry> +<term>Architecture</term> +<listitem> +<para> +When the archive has packages for a single architecture then the Architecture +is listed here. If a mixed set of systems are represented then this should +contain the keyword <emphasis>mixed</emphasis>. +</para> +</listitem> +</varlistentry> +<varlistentry> +<term>NotAutomatic</term> +<listitem> +<para> +A Yes/No flag indicating that the archive is extremely unstable and its +version's should never be automatically selected. This is to be used by +experimental. +</para> +</listitem> +</varlistentry> +<varlistentry> +<term>Description</term> +<listitem> +<para> +Description is used to describe the release. For instance experimental would +contain a warning that the packages have problems. +</para> +</listitem> +</varlistentry> +</variablelist> +<para> +The location of the Release file in the archive is very important, it must be +located in the same location as the packages file so that it can be located in +all situations. The following is an example for the current stable release, +1.3.1r6 +</para> +<screen> +Archive: stable +Component: main +Version: 1.3.1r6 +Origin: Debian +Label: Debian +Architecture: i386 +</screen> +<para> +This is an example of experimental, +</para> +<screen> +Archive: experimental +Version: 0 +Origin: Debian +Label: Debian +Architecture: mixed +NotAutomatic: Yes +</screen> +<para> +And unstable, +</para> +<screen> +Archive: unstable +Component: main +Version: 2.1 +Origin: Debian +Label: Debian +Architecture: i386 +</screen> +</section> + +</chapter> + + +</book> |