# 2. Binary packages (from old Packaging Manual)

See deb(5) and Binary package metadata 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 binary package control 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. Binary package metadata files

The package metadata 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 metadata archive member, but this is not generally a good idea (though they will largely be ignored).

Here is a brief list of the package metadata 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 Debian source package template control files – debian/control and Debian 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 binary package control file: `control`

The most important package metadata 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 Debian 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.