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Diffstat (limited to 'doc')
| -rw-r--r-- | doc/cache.sgml | 824 | ||||
| -rw-r--r-- | doc/files.sgml | 181 |
2 files changed, 78 insertions, 927 deletions
diff --git a/doc/cache.sgml b/doc/cache.sgml deleted file mode 100644 index aea5a45c3..000000000 --- a/doc/cache.sgml +++ /dev/null @@ -1,824 +0,0 @@ -<!-- -*- mode: sgml; mode: fold -*- --> -<!doctype debiandoc PUBLIC "-//DebianDoc//DTD DebianDoc//EN"> -<book> -<title>APT Cache File Format</title> - -<author>Jason Gunthorpe <email>jgg@debian.org</email></author> -<version>$Id: cache.sgml,v 1.11 2003/02/12 15:05:44 doogie Exp $</version> - -<abstract> -This document describes the complete implementation and format of the APT -Cache file. The APT Cache file is a way for APT to parse and store a -large number of package files for display in the UI. It's primary design -goal is to make display of a single package in the tree very fast by -pre-linking important things like dependencies and provides. - -The specification doubles as documentation for one of the in-memory -structures used by the package library and the APT GUI. - -</abstract> - -<copyright> -Copyright © Jason Gunthorpe, 1997-1998. -<p> -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. - -<p> -For more details, on Debian GNU/Linux systems, see the file -/usr/share/common-licenses/GPL for the full license. -</copyright> - -<toc sect> - -<chapt>Introduction -<!-- Purpose {{{ --> -<!-- ===================================================================== --> -<sect>Purpose - -<p> -This document describes the implementation of an architecture -dependent binary cache file. The goal of this cache file is two fold, -firstly to speed loading and processing of the package file array and -secondly to reduce memory consumption of the package file array. - -<p> -The implementation is aimed at an environment with many primary package -files, for instance someone that has a Package file for their CD-ROM, a -Package file for the latest version of the distribution on the CD-ROM and a -package file for the development version. Always present is the information -contained in the status file which might be considered a separate package -file. - -<p> -Please understand, this is designed as a -CACHE FILE- it is not meant to be -used on any system other than the one it was created for. It is not meant to -be authoritative either, i.e. if a system crash or software failure occurs it -must be perfectly acceptable for the cache file to be in an inconsistent -state. Furthermore at any time the cache file may be erased without losing -any information. - -<p> -Also the structures and storage layout is optimized for use by the APT -GUI and may not be suitable for all purposes. However it should be possible -to extend it with associate cache files that contain other information. - -<p> -To keep memory use down the cache file only contains often used fields and -fields that are inexpensive to store, the Package file has a full list of -fields. Also the client may assume that all items are perfectly valid and -need not perform checks against their correctness. Removal of information -from the cache is possible, but blanks will be left in the file, and -unused strings will also be present. The recommended implementation is to -simply rebuild the cache each time any of the data files change. It is -possible to add a new package file to the cache without any negative side -effects. - -<sect1>Note on Pointer access -<p> -Every item in every structure is stored as the index to that structure. -What this means is that once the files is mmaped every data access has to -go through a fixup stage to get a real memory pointer. This is done -by taking the index, multiplying it by the type size and then adding -it to the start address of the memory block. This sounds complex, but -in C it is a single array dereference. Because all items are aligned to -their size and indexes are stored as multiples of the size of the structure -the format is immediately portable to all possible architectures - BUT the -generated files are -NOT-. - -<p> -This scheme allows code like this to be written: -<example> - void *Map = mmap(...); - Package *PkgList = (Package *)Map; - Header *Head = (Header *)Map; - char *Strings = (char *)Map; - cout << (Strings + PkgList[Head->HashTable[0]]->Name) << endl; -</example> -<p> -Notice the lack of casting or multiplication. The net result is to return -the name of the first package in the first hash bucket, without error -checks. - -<p> -The generator uses allocation pools to group similarly sized structures in -large blocks to eliminate any alignment overhead. The generator also -assures that no structures overlap and all indexes are unique. Although -at first glance it may seem like there is the potential for two structures -to exist at the same point the generator never allows this to happen. -(See the discussion of free space pools) - <!-- }}} --> - -<chapt>Structures -<!-- Header {{{ --> -<!-- ===================================================================== --> -<sect>Header -<p> -This is the first item in the file. -<example> - struct Header - { - // Signature information - unsigned long Signature; - short MajorVersion; - short MinorVersion; - bool Dirty; - - // Size of structure values - unsigned short HeaderSz; - unsigned short PackageSz; - unsigned short PackageFileSz; - unsigned short VersionSz; - unsigned short DependencySz; - unsigned short ProvidesSz; - unsigned short VerFileSz; - - // Structure counts - unsigned long PackageCount; - unsigned long VersionCount; - unsigned long DependsCount; - unsigned long PackageFileCount; - - // Offsets - unsigned long FileList; // PackageFile - unsigned long StringList; // StringItem - unsigned long VerSysName; // StringTable - unsigned long Architecture; // StringTable - unsigned long MaxVerFileSize; - - // Allocation pools - struct - { - unsigned long ItemSize; - unsigned long Start; - unsigned long Count; - } Pools[7]; - - // Package name lookup - unsigned long HashTable[2*1024]; // Package - }; -</example> -<taglist> -<tag>Signature<item> -This must contain the hex value 0x98FE76DC which is designed to verify -that the system loading the image has the same byte order and byte size as -the system saving the image - -<tag>MajorVersion -<tag>MinorVersion<item> -These contain the version of the cache file, currently 0.2. - -<tag>Dirty<item> -Dirty is true if the cache file was opened for reading, the client expects -to have written things to it and have not fully synced it. The file should -be erased and rebuilt if it is true. - -<tag>HeaderSz -<tag>PackageSz -<tag>PackageFileSz -<tag>VersionSz -<tag>DependencySz -<tag>VerFileSz -<tag>ProvidesSz<item> -*Sz contains the sizeof() that particular structure. It is used as an -extra consistency check on the structure of the file. - -If any of the size values do not exactly match what the client expects then -the client should refuse the load the file. - -<tag>PackageCount -<tag>VersionCount -<tag>DependsCount -<tag>PackageFileCount<item> -These indicate the number of each structure contained in the cache. -PackageCount is especially useful for generating user state structures. -See Package::Id for more info. - -<tag>VerSysName<item> -String representing the version system used for this cache - -<tag>Architecture<item> -Architecture the cache was built against. - -<tag>MaxVerFileSize<item> -The maximum size of a raw entry from the original Package file -(i.e. VerFile::Size) is stored here. - -<tag>FileList<item> -This contains the index of the first PackageFile structure. The PackageFile -structures are singly linked lists that represent all package files that -have been merged into the cache. - -<tag>StringList<item> -This contains a list of all the unique strings (string item type strings) in -the cache. The parser reads this list into memory so it can match strings -against it. - -<tag>Pools<item> -The Pool structures manage the allocation pools that the generator uses. -Start indicates the first byte of the pool, Count is the number of objects -remaining in the pool and ItemSize is the structure size (alignment factor) -of the pool. An ItemSize of 0 indicates the pool is empty. There should be -the same number of pools as there are structure types. The generator -stores this information so future additions can make use of any unused pool -blocks. - -<tag>HashTable<item> -HashTable is a hash table that provides indexing for all of the packages. -Each package name is inserted into the hash table using the following has -function: -<example> - unsigned long Hash(string Str) - { - unsigned long Hash = 0; - for (const char *I = Str.begin(); I != Str.end(); I++) - Hash += *I * ((Str.end() - I + 1)); - return Hash % _count(Head.HashTable); - } -</example> -<p> -By iterating over each entry in the hash table it is possible to iterate over -the entire list of packages. Hash Collisions are handled with a singly linked -list of packages based at the hash item. The linked list contains only -packages that match the hashing function. - -</taglist> - <!-- }}} --> -<!-- Package {{{ --> -<!-- ===================================================================== --> -<sect>Package -<p> -This contains information for a single unique package. There can be any -number of versions of a given package. Package exists in a singly -linked list of package records starting at the hash index of the name in -the Header->HashTable. -<example> - struct Pacakge - { - // Pointers - unsigned long Name; // Stringtable - unsigned long VersionList; // Version - unsigned long CurrentVer; // Version - unsigned long Section; // StringTable (StringItem) - - // Linked lists - unsigned long NextPackage; // Package - unsigned long RevDepends; // Dependency - unsigned long ProvidesList; // Provides - - // Install/Remove/Purge etc - unsigned char SelectedState; // What - unsigned char InstState; // Flags - unsigned char CurrentState; // State - - // Unique ID for this pkg - unsigned short ID; - unsigned long Flags; - }; -</example> - -<taglist> -<tag>Name<item> -Name of the package. - -<tag>VersionList<item> -Base of a singly linked list of version structures. Each structure -represents a unique version of the package. The version structures -contain links into PackageFile and the original text file as well as -detailed information about the size and dependencies of the specific -package. In this way multiple versions of a package can be cleanly handled -by the system. Furthermore, this linked list is guaranteed to be sorted -from Highest version to lowest version with no duplicate entries. - -<tag>CurrentVer<item> -CurrentVer is an index to the installed version, either can be -0. - -<tag>Section<item> -This indicates the deduced section. It should be "Unknown" or the section -of the last parsed item. - -<tag>NextPackage<item> -Next link in this hash item. This linked list is based at Header.HashTable -and contains only packages with the same hash value. - -<tag>RevDepends<item> -Reverse Depends is a linked list of all dependencies linked to this package. - -<tag>ProvidesList<item> -This is a linked list of all provides for this package name. - -<tag>SelectedState -<tag>InstState -<tag>CurrentState<item> -These correspond to the 3 items in the Status field found in the status -file. See the section on defines for the possible values. -<p> -SelectedState is the state that the user wishes the package to be -in. -<p> -InstState is the installation state of the package. This normally -should be OK, but if the installation had an accident it may be otherwise. -<p> -CurrentState indicates if the package is installed, partially installed or -not installed. - -<tag>ID<item> -ID is a value from 0 to Header->PackageCount. It is a unique value assigned -by the generator. This allows clients to create an array of size PackageCount -and use it to store state information for the package map. For instance the -status file emitter uses this to track which packages have been emitted -already. - -<tag>Flags<item> -Flags are some useful indicators of the package's state. - -</taglist> - - <!-- }}} --> -<!-- PackageFile {{{ --> -<!-- ===================================================================== --> -<sect>PackageFile -<p> -This contains information for a single package file. Package files are -referenced by Version structures. This is a singly linked list based from -Header.FileList -<example> - struct PackageFile - { - // Names - unsigned long FileName; // Stringtable - unsigned long Archive; // Stringtable - unsigned long Component; // Stringtable - unsigned long Version; // Stringtable - unsigned long Origin; // Stringtable - unsigned long Label; // Stringtable - unsigned long Architecture; // Stringtable - unsigned long Site; // Stringtable - unsigned long IndexType; // Stringtable - unsigned long Size; - - // Linked list - unsigned long NextFile; // PackageFile - unsigned short ID; - unsigned long Flags; - time_t mtime; // Modification time - }; -</example> -<taglist> - -<tag>FileName<item> -Refers the the physical disk file that this PacakgeFile represents. - -<tag>Archive -<tag>Component -<tag>Version -<tag>Origin -<tag>Label -<tag>Architecture -<tag>NotAutomatic<item> -This is the release information. Please see the files document for a -description of what the release information means. - -<tag>Site<item> -The site the index file was fetched from. - -<tag>IndexType<item> -A string indicating what sort of index file this is. - -<tag>Size<item> -Size is provided as a simple check to ensure that the package file has not -been altered. - -<tag>ID<item> -See Package::ID. - -<tag>Flags<item> -Provides some flags for the PackageFile, see the section on defines. - -<tag>mtime<item> -Modification time for the file at time of cache generation. - -</taglist> - - <!-- }}} --> -<!-- Version {{{ --> -<!-- ===================================================================== --> -<sect>Version -<p> -This contains the information for a single version of a package. This is a -single linked list based from Package.Versionlist. - -<p> -The version list is always sorted from highest version to lowest version by -the generator. Also there may not be any duplicate entries in the list (same -VerStr). - -<example> - struct Version - { - unsigned long VerStr; // Stringtable - unsigned long Section; // StringTable (StringItem) - unsigned long Arch; // StringTable - - // Lists - unsigned long FileList; // VerFile - unsigned long NextVer; // Version - unsigned long DependsList; // Dependency - unsigned long ParentPkg; // Package - unsigned long ProvidesList; // Provides - - unsigned long Size; - unsigned long InstalledSize; - unsigned long Hash; - unsigned short ID; - unsigned char Priority; - }; -</example> -<taglist> - -<tag>VerStr<item> -This is the complete version string. - -<tag>FileList<item> -References the all the PackageFile's that this version came out of. FileList -can be used to determine what distribution(s) the Version applies to. If -FileList is 0 then this is a blank version. The structure should also have -a 0 in all other fields excluding VerStr and Possibly NextVer. - -<tag>Section<item> -This string indicates which section it is part of. The string should be -contained in the StringItem list. - -<tag>Arch<item> -Architecture the package was compiled for. - -<tag>NextVer<item> -Next step in the linked list. - -<tag>DependsList<item> -This is the base of the dependency list. - -<tag>ParentPkg<item> -This links the version to the owning package, allowing reverse dependencies -to determine the package. - -<tag>ProvidesList<item> -Head of the linked list of Provides::NextPkgProv, forward provides. - -<tag>Size -<tag>InstalledSize<item> -The archive size for this version. For Debian this is the size of the .deb -file. Installed size is the uncompressed size for this version - -<tag>Hash<item> -This is a characteristic value representing this package. No two packages -in existence should have the same VerStr and Hash with different contents. - -<tag>ID<item> -See Package::ID. - -<tag>Priority<item> -This is the parsed priority value of the package. -</taglist> - - <!-- }}} --> -<!-- Dependency {{{ --> -<!-- ===================================================================== --> -<sect>Dependency -<p> -Dependency contains the information for a single dependency record. The records -are split up like this to ease processing by the client. The base of list -linked list is Version.DependsList. All forms of dependencies are recorded -here including Conflicts, Breaks, Suggests and Recommends. - -<p> -Multiple depends on the same package must be grouped together in -the Dependency lists. Clients should assume this is always true. - -<example> - struct Dependency - { - unsigned long Version; // Stringtable - unsigned long Package; // Package - unsigned long NextDepends; // Dependency - unsigned long NextRevDepends; // Reverse dependency linking - unsigned long ParentVer; // Upwards parent version link - - // Specific types of depends - unsigned char Type; - unsigned char CompareOp; - unsigned short ID; - }; -</example> -<taglist> -<tag>Version<item> -The string form of the version that the dependency is applied against. - -<tag>Package<item> -The index of the package file this depends applies to. If the package file -does not already exist when the dependency is inserted a blank one (no -version records) should be created. - -<tag>NextDepends<item> -Linked list based off a Version structure of all the dependencies in that -version. - -<tag>NextRevDepends<item> -Reverse dependency linking, based off a Package structure. This linked list -is a list of all packages that have a depends line for a given package. - -<tag>ParentVer<item> -Parent version linking, allows the reverse dependency list to link -back to the version and package that the dependency are for. - -<tag>Type<item> -Describes weather it is depends, predepends, recommends, suggests, etc. - -<tag>CompareOp<item> -Describes the comparison operator specified on the depends line. If the high -bit is set then it is a logical or with the previous record. - -<tag>ID<item> -See Package::ID. - -</taglist> - - <!-- }}} --> -<!-- Provides {{{ --> -<!-- ===================================================================== --> -<sect>Provides -<p> -Provides handles virtual packages. When a Provides: line is encountered -a new provides record is added associating the package with a virtual -package name. The provides structures are linked off the package structures. -This simplifies the analysis of dependencies and other aspects A provides -refers to a specific version of a specific package, not all versions need to -provide that provides. - -<p> -There is a linked list of provided package names started from each -version that provides packages. This is the forwards provides mechanism. -<example> - struct Provides - { - unsigned long ParentPkg; // Package - unsigned long Version; // Version - unsigned long ProvideVersion; // Stringtable - unsigned long NextProvides; // Provides - unsigned long NextPkgProv; // Provides - }; -</example> -<taglist> -<tag>ParentPkg<item> -The index of the package that head of this linked list is in. ParentPkg->Name -is the name of the provides. - -<tag>Version<item> -The index of the version this provide line applies to. - -<tag>ProvideVersion<item> -Each provides can specify a version in the provides line. This version allows -dependencies to depend on specific versions of a Provides, as well as allowing -Provides to override existing packages. This is experimental. - -<tag>NextProvides<item> -Next link in the singly linked list of provides (based off package) - -<tag>NextPkgProv<item> -Next link in the singly linked list of provides for 'Version'. - -</taglist> - - <!-- }}} --> -<!-- VerFile {{{ --> -<!-- ===================================================================== --> -<sect>VerFile -<p> -VerFile associates a version with a PackageFile, this allows a full -description of all Versions in all files (and hence all sources) under -consideration. - -<example> - struct pkgCache::VerFile - { - unsigned long File; // PackageFile - unsigned long NextFile; // PkgVerFile - unsigned long Offset; - unsigned short Size; - } -</example> -<taglist> -<tag>File<item> -The index of the package file that this version was found in. - -<tag>NextFile<item> -The next step in the linked list. - -<tag>Offset -<tag>Size<item> -These describe the exact position in the package file for the section from -this version. -</taglist> - - <!-- }}} --> -<!-- StringItem {{{ --> -<!-- ===================================================================== --> -<sect>StringItem -<p> -StringItem is used for generating single instances of strings. Some things -like Section Name are are useful to have as unique tags. It is part of -a linked list based at Header::StringList. -<example> - struct StringItem - { - unsigned long String; // Stringtable - unsigned long NextItem; // StringItem - }; -</example> -<taglist> -<tag>String<item> -The string this refers to. - -<tag>NextItem<item> -Next link in the chain. -</taglist> - <!-- }}} --> -<!-- StringTable {{{ --> -<!-- ===================================================================== --> -<sect>StringTable -<p> -All strings are simply inlined any place in the file that is natural for the -writer. The client should make no assumptions about the positioning of -strings. All stringtable values point to a byte offset from the start of the -file that a null terminated string will begin. - <!-- }}} --> -<!-- Defines {{{ --> -<!-- ===================================================================== --> -<sect>Defines -<p> -Several structures use variables to indicate things. Here is a list of all -of them. - -<sect1>Definitions for Dependency::Type -<p> -<example> -#define pkgDEP_Depends 1 -#define pkgDEP_PreDepends 2 -#define pkgDEP_Suggests 3 -#define pkgDEP_Recommends 4 -#define pkgDEP_Conflicts 5 -#define pkgDEP_Replaces 6 -#define pkgDEP_Breaks 8 -</example> -</sect1> - -<sect1>Definitions for Dependency::CompareOp -<p> -<example> -#define pkgOP_OR 0x10 -#define pkgOP_LESSEQ 0x1 -#define pkgOP_GREATEREQ 0x2 -#define pkgOP_LESS 0x3 -#define pkgOP_GREATER 0x4 -#define pkgOP_EQUALS 0x5 -</example> -The lower 4 bits are used to indicate what operator is being specified and -the upper 4 bits are flags. pkgOP_OR indicates that the next package is -or'd with the current package. -</sect1> - -<sect1>Definitions for Package::SelectedState -<p> -<example> -#define pkgSTATE_Unkown 0 -#define pkgSTATE_Install 1 -#define pkgSTATE_Hold 2 -#define pkgSTATE_DeInstall 3 -#define pkgSTATE_Purge 4 -</example> -</sect1> - -<sect1>Definitions for Package::InstState -<p> -<example> -#define pkgSTATE_Ok 0 -#define pkgSTATE_ReInstReq 1 -#define pkgSTATE_Hold 2 -#define pkgSTATE_HoldReInstReq 3 -</example> -</sect1> - -<sect1>Definitions for Package::CurrentState -<p> -<example> -#define pkgSTATE_NotInstalled 0 -#define pkgSTATE_UnPacked 1 -#define pkgSTATE_HalfConfigured 2 -#define pkgSTATE_UnInstalled 3 -#define pkgSTATE_HalfInstalled 4 -#define pkgSTATE_ConfigFiles 5 -#define pkgSTATE_Installed 6 -#define pkgSTATE_TriggersAwaited 7 -#define pkgSTATE_TriggersPending 8 -</example> -</sect1> - -<sect1>Definitions for Package::Flags -<p> -<example> -#define pkgFLAG_Auto (1 << 0) -#define pkgFLAG_New (1 << 1) -#define pkgFLAG_Obsolete (1 << 2) -#define pkgFLAG_Essential (1 << 3) -#define pkgFLAG_ImmediateConf (1 << 4) -</example> -</sect1> - -<sect1>Definitions for Version::Priority -<p> -Zero is used for unparsable or absent Priority fields. -<example> -#define pkgPRIO_Important 1 -#define pkgPRIO_Required 2 -#define pkgPRIO_Standard 3 -#define pkgPRIO_Optional 4 -#define pkgPRIO_Extra 5 -</example> -</sect1> - -<sect1>Definitions for PackageFile::Flags -<p> -<example> -#define pkgFLAG_NotSource (1 << 0) -#define pkgFLAG_NotAutomatic (1 << 1) -</example> -</sect1> - - <!-- }}} --> - -<chapt>Notes on the Generator -<!-- Notes on the Generator {{{ --> -<!-- ===================================================================== --> -<p> -The pkgCache::MergePackageFile function is currently the only generator of -the cache file. It implements a conversion from the normal textual package -file into the cache file. - -<p> -The generator assumes any package declaration with a -Status: line is a 'Status of the package' type of package declaration. -A Package with a Target-Version field should also really have a status field. -The processing of a Target-Version field can create a place-holder Version -structure that is empty to refer to the specified version (See Version -for info on what a empty Version looks like). The Target-Version syntax -allows the specification of a specific version and a target distribution. - -<p> -Different section names on different versions is supported, but I -do not expect to use it. To simplify the GUI it will merely use the section -in the Package structure. This should be okay as I hope sections do not change -much. - -<p> -The generator goes through a number of post processing steps after producing -a disk file. It sorts all of the version lists to be in descending order -and then generates the reverse dependency lists for all of the packages. -ID numbers and count values are also generated in the post processing step. - -<p> -It is possible to extend many of the structures in the cache with extra data. -This is done by using the ID member. ID will be a unique number from 0 to -Header->??Count. For example -<example> -struct MyPkgData; -MyPkgData *Data = new MyPkgData[Header->PackageCount]; -Data[Package->ID]->Item = 0; -</example> -This provides a one way reference between package structures and user data. To -get a two way reference would require a member inside the MyPkgData structure. - -<p> -The generators use of free space pools tend to make the package file quite -large, and quite full of blank space. This could be fixed with sparse files. - - <!-- }}} --> - -<chapt>Future Directions -<!-- Future Directions {{{ --> -<!-- ===================================================================== --> -<p> -Some good directions to take the cache file is into a cache directory that -contains many associated caches that cache other important bits of -information. (/var/cache/apt, FHS2) - -<p> -Caching of the info/*.list is an excellent place to start, by generating all -the list files into a tree structure and reverse linking them to the package -structures in the main cache file major speed gains in dpkg might be achieved. - - <!-- }}} --> - -</book> diff --git a/doc/files.sgml b/doc/files.sgml index 2293e204a..108e73670 100644 --- a/doc/files.sgml +++ b/doc/files.sgml @@ -42,40 +42,68 @@ multiple package files. The var directory structure is as follows: <example> /var/lib/apt/ - lists/ + lists/ partial/ - xstatus - userstatus - cdroms.list + periodic/ + extended_states + cdroms.list /var/cache/apt/ - pkgcache.bin - srcpkgcache.bin archives/ partial/ + pkgcache.bin + srcpkgcache.bin /etc/apt/ - sources.list - apt.conf + sources.list.d/ + apt.conf.d/ + preferences.d/ + trusted.gpg.d/ + sources.list + apt.conf + apt_preferences + trusted.gpg /usr/lib/apt/ - methods/ - cdrom - ftp - http - file - gzip - copy + methods/ + bzip2 + cdrom + copy + file + ftp + gpgv + gzip + http + https + lzma + rred + rsh + ssh </example> <p> 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. +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. </sect> <!-- }}} --> <chapt>Files <!-- Distribution Source List {{{ --> <!-- ===================================================================== --> +<sect>Files and fragment directories in /etc/apt + +<p> +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. + +</sect> + <sect>Distribution Source list (sources.list) <p> @@ -121,7 +149,10 @@ which indicates a standard debian archive with a dists dir. <sect1>URI specification <p> -URIs in the source list support a large number of access schemes. +URIs in the source list support a large number of access schemes which +are listed in the sources.list manpage and can be further extended by +transport binaries placed in /usr/lib/apt/methods. The most important +builtin schemes are: <taglist> <tag>cdrom<item> @@ -161,13 +192,6 @@ URIs in the source list support a large number of access schemes. <example> file:/var/debian </example> - -<tag>smb<item> - A possible future expansion may be to have direct support for smb (Samba - servers). - <example> - smb://ftp.kernel.org/pub/mirrors/debian - </example> </taglist> </sect1> @@ -201,38 +225,31 @@ here as well. </sect> <!-- }}} --> -<!-- Extra Status {{{ --> +<!-- Extended Status {{{ --> <!-- ===================================================================== --> -<sect>Extra Status File (xstatus) +<sect>Extended States File (extended_states) <p> -The extra status file serves the same purpose as the normal dpkg status file +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 the autoflag, target distribution and version and any other -unique features that come up over time. It duplicates nothing from the normal +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 behaviour of these fields. The Package field is -placed directly before the new fields to indicate which package they -apply to. The new fields are as follows: +of the exact internal behaviour 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: <taglist> -<tag>X-Auto<item> - The Auto flag can be Yes or No and controls whether the package is in - auto mode. - -<tag>X-TargetDist<item> - The TargetDist item indicates which distribution versions are offered for - installation from. It should be stable, unstable or testing. - -<tag>X-TargetVersion<item> - The target version item is set if the user selects a specific version, it - overrides the TargetDist selection if both are present. +<tag>Auto-Installed<item> + The Auto flag can be 1 (Yes) or 0 (No) and controls whether the package + was automatical installed to satisfy a dependency or if the user requested + the installation </taglist> </sect> <!-- }}} --> <!-- Binary Package Cache {{{ --> <!-- ===================================================================== --> -<sect>Binary Package Cache (pkgcache.bin) +<sect>Binary Package Cache (srcpkgcache.bin and pkgcache.bin) <p> Please see cache.sgml for a complete description of what this file is. The @@ -278,69 +295,27 @@ The Methods directory is more fully described in the APT Methods interface document. </sect> <!-- }}} --> -<!-- The Mirror List {{{ --> +<!-- The Configuration File {{{ --> <!-- ===================================================================== --> -<sect> The Mirror List +<sect> The Configuration File (/etc/apt/apt.conf) <p> -The mirror list is stored on the primary debian web server (www.debian.org) -and contains a machine readable list of all known debian mirrors. It's -format and style mirror the Package file. - -<taglist> -<tag>Site<item> -This is the proper host name of the site. It should not be a host within -debian.org and generally cnames should be avoided here. - -<tag>Aliases<item> -These list any commonly used aliases for the site. This field is used to make -sure that a site is not added twice. - -<tag>Type<item> -This field can either be <em>Push-Primary</> or <em>leaf</>. -<em>Push-Primary</> are authorized top level mirrors of the archive, all -other mirrors are leaf. - -<tag>Archive-[access]<item> -The Archive field gives the path(s) to the debian archive. [access] -specifies the access method and may be one of ftp, http, rsync, nfs, or -smb. For many of the types it is possible to prefix the path with :### -indicating that an alternate port should be used. Generally paths -start with a / and end with a /, rsync is an exception in that the -first directory component is not a path but a label. - -<tag>WWW-[access]<item> -The WWW field gives the path(s) to the debian web site. - -<tag>CDImage-[access]<item> -The WWW field gives the path(s) to the debian CD-ROM images - -<tag>Incoming-[access]<item> -The Incoming field gives the path(s) to a mirror of the debian incoming -directory. - -<tag>nonUS-[access]<item> -The nonUS field gives the path(s) to a mirror of the non-US distribution. - -<tag>Maintainer<item> -This is the email address of the maintainer of the mirror. - -<tag>Location<item> -Location gives the general geographical region the mirror is in. - -<tag>Sponsor<item> -The Sponsor field indicates who owns the mirror and a URL to a web page -describing the organization. - -<tag>Comment<item> -General free-form text. - -</taglist> +The configuration file (and the associated fragments directory +/etc/apt/apt.conf.d/) is described in the apt.conf manpage. +</sect> + <!-- }}} --> +<!-- The trusted.gpg File {{{ --> +<!-- ===================================================================== --> +<sect> The trusted.gpg File (/etc/apt/trusted.gpg) <p> -Some form of network measurement will have to be used to gauge performance -of each of the mirrors. This will be discussed later, initial versions -will use the first found URI. +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. </sect> <!-- }}} --> <!-- The Release File {{{ --> @@ -348,7 +323,7 @@ will use the first found URI. <sect> The Release File <p> -This file plays and important role in how APT presents the archive to the +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 |