2. Binary packages (from old Packaging Manual)

See deb(5) and Package control information files.

2.1. Creating package files - dpkg-deb

All manipulation of binary package files is done by dpkg-deb; it’s the only program that has knowledge of the format. (dpkg-deb may be invoked by calling dpkg, as dpkg will spot that the options requested are appropriate to dpkg-deb and invoke that instead with the same arguments.)

In order to create a binary package, you must make a directory tree which contains all the files and directories you want to have in the file system data part of the package. In Debian-format source packages, this directory is usually either debian/tmp or debian/pkg, relative to the top of the package’s source tree.

They should have the locations (relative to the root of the directory tree you’re constructing) ownerships and permissions which you want them to have on the system when they are installed.

With current versions of dpkg the uid/username and gid/groupname mappings for the users and groups being used should be the same on the system where the package is built and the one where it is installed.

You need to add one special directory to the root of the miniature file system tree you’re creating: DEBIAN. It should contain the control information files, notably the binary package control file (see The main control information file: control).

The DEBIAN directory will not appear in the file system archive of the package, and so won’t be installed by dpkg when the package is unpacked.

When you’ve prepared the package, you should invoke:

dpkg --build directory

This will build the package in directory.deb. (dpkg knows that --build is a dpkg-deb option, so it invokes dpkg-deb with the same arguments to build the package.)

See the dpkg-deb(8) man page for details of how to examine the contents of this newly-created file. You may find the output of following commands enlightening:

dpkg-deb --info filename.deb
dpkg-deb --contents filename.deb
dpkg --contents filename.deb

To view the copyright file for a package you could use this command:

dpkg --fsys-tarfile filename.deb | tar xOf - --wildcards \*/copyright | pager

2.2. Package control information files

The control information portion of a binary package is a collection of files with names known to dpkg. It will treat the contents of these files specially - some of them contain information used by dpkg when installing or removing the package; others are scripts which the package maintainer wants dpkg to run.

It is possible to put other files in the package control information file area, but this is not generally a good idea (though they will largely be ignored).

Here is a brief list of the control information files supported by dpkg and a summary of what they’re used for.

control

This is the key description file used by dpkg. It specifies the package’s name and version, gives its description for the user, states its relationships with other packages, and so forth. See Source package control files – debian/control and Binary package control files – DEBIAN/control.

It is usually generated automatically from information in the source package by the dpkg-gencontrol program, and with assistance from dpkg-shlibdeps. See Source packages (from old Packaging Manual).

postinst, preinst, postrm, prerm

These are executable files (usually scripts) which dpkg runs during installation, upgrade and removal of packages. They allow the package to deal with matters which are particular to that package or require more complicated processing than that provided by dpkg. Details of when and how they are called are in Package maintainer scripts and installation procedure.

It is very important to make these scripts idempotent. See Maintainer scripts idempotency.

The maintainer scripts are not guaranteed to run with a controlling terminal and may not be able to interact with the user. See Controlling terminal for maintainer scripts.

conffiles This file contains a list of configuration files which

are to be handled automatically by dpkg (see Configuration file handling (from old Packaging Manual)). Note that not necessarily every configuration file should be listed here.

shlibs

This file contains a list of the shared libraries supplied by the package, with dependency details for each. This is used by dpkg-shlibdeps when it determines what dependencies are required in a package control file. The shlibs file format is described on The shlibs File Format.

2.3. The main control information file: control

The most important control information file used by dpkg when it installs a package is control. It contains all the package’s “vital statistics”.

The binary package control files of packages built from Debian sources are made by a special tool, dpkg-gencontrol, which reads debian/control and debian/changelog to find the information it needs. See Source packages (from old Packaging Manual) for more details.

The fields in binary package control files are listed in Binary package control files – DEBIAN/control.

A description of the syntax of control files and the purpose of the fields is available in Control files and their fields.

2.4. Time Stamps

See Time Stamps.