It can be quite useful to be able to distribute your own Debian packages using apt, without having to push them to the Debian project itself. Doing this properly requires several steps:

Each of these steps is covered here. Before you start, you should probably look at these HOWTO's on this subject:

Generating GnuPG keys

GnuPG is used here for two purposes:

In general, you only need to run this command on the computer hosting the apt repository:

$ gpg --gen-key

However, if you're setting up the apt repository on a remote server, you'll probably have issues generating enough entropy for key generation. In this case, you can generate the keypair on a local workstation (=one with a keyboard and a mouse), export the keys and import them into the repository server. This is described in detail in this article.

For further details on GnuPG + apt + dpkg take a look here

Signing Debian packages

First install dpkg-sig:

$ apt-get install dpkg-sig

Then sign your package(s):

dpkg-sig -k keyid --sign builder your_packages_<version>_<architecture>.deb

Refer to this article for more details.

Configuring Apache

Here we assume you got Apache (2.x) running already, and serving web pages - even if only the default index.html. First you need a directory for the apt repository:

$ mkdir -p /var/www/repos/apt/debian

Next you should add Apache rules to make a few directories used internally by reprepro invisible to users of your repository. Add something like this to a Apache server configuration file fragment (e.g. /etc/apache2/conf.d/repos) or to a virtualhost definition:

# /etc/apache2/conf.d/repos

<Directory /var/www/repos/ >
        # We want the user to be able to browse the directory manually
        Options Indexes FollowSymLinks Multiviews
        Order allow,deny
        Allow from all

# This syntax supports several repositories, e.g. one for Debian, one for Ubuntu.
# Replace * with debian, if you intend to support one distribution only.
<Directory "/var/www/repos/apt/*/db/">
        Order allow,deny
        Deny from all

<Directory "/var/www/repos/apt/*/conf/">
        Order allow,deny
        Deny from all

<Directory "/var/www/repos/apt/*/incoming/">
        Order allow,deny
        Deny from all

This allows users to browse the pool directory with the browser, should he/she want to. The configuration also blocks a few directories used by reprepro internally, without affecting normal apt usage. Finally check that the configuration is sane and reload it:

$ apache2ctl configtest
Syntax OK
$ /etc/init.d/apache2 reload
Reloading web server config: apache2.

Configuring reprepro

Reprepro eases the task of creating apt-compatible directory layout, apt-specific files and databases and removing and adding packages to the repository. First you need to create a reprepro configuration directory:

$ mkdir -p /var/www/repos/apt/debian/conf

You also need to put three files into that conf directory. First, you need the distributions file. In my case, this file is called /var/www/repos/apt/debian/conf/distributions:

Origin: Your project name
Label: Your project name
Codename: <osrelease>
Architectures: i386 amd64
Components: main
Description: Apt repository for project x
DebOverride: override.<osrelease>
DscOverride: override.<osrelease>
SignWith: <key-id>

Above <osrelease> is an official Debian release name (e.g. Lenny or Squeeze) and <key-id> the ID of the GnuPG key you generated. You can check the key ID with gpg:

$ gpg --list-keys
pub   2048R/E123D553 2011-08-03 [expires: 2012-08-02]
uid                  Joe User (Some organization) <>
sub   2048R/F2495744 2011-08-03 [expires: 2012-08-02]

Here <keyid> for the public key is !F2495744 (that's technically the subkey, which is recommended to be used for this sort of signing purpose)

Next should add an options file to make daily life with reprepro command-line a little easier. This file is in /var/www/repos/apt/debian/conf/options:

basedir /var/www/repos/apt/debian

Finally, you need an override file where you add some additional metadata foreach package. This file is saved to /var/www/repos/apt/debian/conf/override.<osrelease>, where <osrelease> is an official Debian release name such as Lenny or Squeeze:

your_package_name Priority        optional
your_package_name Section         net

For further details, refer to the instruction given here and here.

Adding packages to the repository

Once all of the above is done, you can add packages to the repository. Reprepro takes care of signing and all, so this should suffice:

$ reprepro includedeb <osrelease> <debfile>

Again, <osrelease> is something like Lenny or Squeeze. Reprepro should prompt you for the GnuPG password, because options file contains the ask-passphrase configuration option. See man reprepro for more options, e.g. how to import a package's changes file to the repository.

Exporting the public GnuPG key

Finally, you need to export the public part of your GnuPG keypair from the keychain:

$ gpg --armor --output whatever.gpg.key --export <key-id>

Copy this to a webserver so that users can download it and add it to their GnuPG keychains similarly to this (as root):

$ wget -O -<whatever>.gpg.key|apt-key add -

Creating a sources.list.d file

If you want to make things easy for the users, you can create a list file for them and put it to a webserver. Its contents should be something like this:

deb <osrelease> main

Instruct the users to copy this file to /etc/apt/sources.list.d/<something>.list. After this, it's just a matter of doing the following to install your package:

$ apt-get update && apt-get install <your-package-name>

Using better verification

You should ensure that your OpenPGP key is of sufficient size and does not use weak hashes.

When importing packages from Debian you might find that you are missing SHA-1 and SHA-256 hashes in your apt metadata (Release/Packages/Sources files). To rectify this reprepro has a redochecksums command that you should run.