diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/acquire-additional-files.txt | 87 | ||||
| -rw-r--r-- | doc/apt-get.8.xml | 15 |
2 files changed, 98 insertions, 4 deletions
diff --git a/doc/acquire-additional-files.txt b/doc/acquire-additional-files.txt index ab833440b..a47dac2d4 100644 --- a/doc/acquire-additional-files.txt +++ b/doc/acquire-additional-files.txt @@ -47,11 +47,13 @@ All files which should be downloaded (nicknamed 'Targets') are mentioned below the APT::Acquire::Targets scope. 'deb' is here the type of the sources.list entry the file should be acquired for. The only other supported value is hence 'deb-src'. Beware: You can't specify multiple -types here and you can't download the same MetaKey form multiple types! +types here and you can't download the same (evaluated) MetaKey from +multiple types! After the type you can pick any valid and unique string which preferable refers to the file it downloads (In the example we picked 'Packages'). -This string is never shown or used. +This string is used as identifier for the target class and accessible as +'Created-By' e.g. in the "apt-get files" output as detailed below. All targets have three main properties you can define: * MetaKey: The identifier of the file to be downloaded as used in the @@ -123,11 +125,12 @@ by the acquire system. The following variables are known; note that unknown variables have no default value nor are they touched: They are printed literally. -* $(SITE): An identifier of the site we access, e.g. - "http://example.org/". +* $(SITE): An identifier of the site we access as seen in sources.list, + e.g. "http://example.org/debian" or "file:/path/to/a/repository". * $(RELEASE): This is usually an archive- or codename, e.g. "stable" or "stretch". Note that flat-style repositories do not have a archive- or codename per-se, so the value might very well be just "/" or so. + Again, as seen in the sources.list. * $(COMPONENT): as given in the sources.list, e.g. "main", "non-free" or "universe". Note that flat-style repositories again do not really have a meaningful value here. @@ -137,3 +140,79 @@ printed literally. APT::Architectures (potentially modified by sources.list options), e.g. "amd64", "i386" or "armel" for the 'deb' type. In type 'deb-src' this variable has the value "source". + +Note that while more variables might exist in the implementation, these +are to be considered undefined and their usage strongly discouraged. If +you have a need for another variable contact us instead. + +# Accessing files + +Do NOT hardcode specific file locations, names or compression types in +your application! You will notice that the configuration options give +you no choice over where the downloaded files will be stored. This is by +design so multiple applications can download and use the same file +rather than each and every one of them potentially downloads and uses +its own copy somewhere on disk. + +"apt-get files" can be used to get the location as well as other +information about all files downloaded (aka: you will see Packages, +Sources and Translation-* files here as well). Provide a line of the +default output format as parameter to filter out all entries which do +not have such a line. With --format, you can further more define your +own output style. The variables are what you see in the output, just all +uppercase and wrapped in $(), as in the configuration file. + +To get all the filenames of all Translation-en files you can e.g. call: + apt-get files --format '$(FILENAME)' "Created-By: Translations" "Language: en" + +Accessing this information via libapt is done by reading the +sources.lists (pkgSourceList), iterating over the metaIndex objects this +creates and calling GetIndexTargets() on them. See the sourcecode of +"apt-get files" for a complete example. + +Remarks on the available fields: +* MetaKey, ShortDesc, Description, Site, Release: as defined + by the configuration and described further above. +* Created-By: configuration entity responsible for this target +* Target-Of: type of the sources.list entry +* URI, Repo-URI: avoid using. Contains potentially username/password. + Prefer 'Site', especially for display. +* Filename: The mentioned file doesn't need to exist, e.g. because the + file wasn't downloaded yet – or it does exist compressed. libapt users + are encouraged to use FileFd to open such files as it can handle + decompression transparently. +* Trusted: As of the last 'apt-get update' call denoting if e.g. apt-get + would print the unauthenticated warning while installing packages + mentioned in this file (example assumes Packages file) [Not really + a property of the target itself, but of the metaIndex]. +* Optional: Decodes the option of the same name from the configuration. + Note that it is using 'yes' and 'no' instead of 'true' and 'false'. +* Language, Architecture, Component: as defined further above, but with + the catch that they might be missing if they don't effect the target + (aka: They weren't used while evaluating the MetaKey template). + +Again, additional fields might be visible in certain implementation, but +you should avoid using them and instead talk to us about a portable +implementation. + +# Multiple application requiring the same files + +It is highly encouraged that applications talk to each other and to us +about which files they require. It is usually best to have a common +package ship the configuration needed to get the files, but specific +needs might require specific solutions. Again: talk to us. + +# Acquiring files not mentioned in the Release file + +You can't. This is by design as these files couldn't be verified to not +be modified in transit, corrupted by the download process or simple if +they are present at all on the server, which would require apt to probe +for them. APT did this in the past for legacy reasons, we do not intend +to go back to these dark times. + +This is also why you can't request files from a different server. It +would have the additional problem that this server might not even be +accessible (e.g. proxy settings) or that local sources (file:/, cdrom:/) +start requesting online files… + +In other words: We would be opening Pandora's box. diff --git a/doc/apt-get.8.xml b/doc/apt-get.8.xml index a372a0d30..da077afa7 100644 --- a/doc/apt-get.8.xml +++ b/doc/apt-get.8.xml @@ -243,6 +243,21 @@ </listitem> </varlistentry> + <varlistentry><term><option>files</option></term> + <listitem><para>Displays by default a deb822 formatted listing of + information about all data files <command>apt-get + update</command> would download. Supports a + <option>--format</option> option to modify the output format as + well as accepts lines of the default output to filter the records + by. The command is mainly used as an interface for external tools + working with APT to get information as well as filenames for + downloaded files so they can use them as well instead of + downloading them again on their own. Detailed documentation is + omitted here and can instead be found in the source tree in + <literal><filename>doc/acquire-additional-files.txt</filename></literal>. + </para> + </listitem> + </varlistentry> </variablelist> |