This is a small howto that explains how to build custom exim4 packages on debian.

It was tested with both exim 4.63 ( on debian etch ) and exim 4.69 ( on debian testing/lenny ) .

I needed to build a custom exim email server that would be built with domainkeys and/or dkim support for signing outgoing messages.

So here are the 12 steps I took to get this done:

1. Create a directory named exim where all activity will take place.
2. Make sure you have the 'source' URIs in your source.list file.
   If you don't have them put them in  and then run apt-get update
3. Install packages required for creating a custom package and building it:

4. Install exim4 source package:

5. unpack standard configuration files:

6. Define the new package name. In this step we just put the new package name in a variable and export it in the environment to make the next steps easier. You can use anything for the package name ( actually it's just a package name suffix ) but I recommend using 'custom' for the package name for one main reason: dependencies. Packages that depend on exim4-daemon-light or exim4-daemon-heavy (like sa-exim, mailx and maybe others ) already accept exim4-daemon-custom as a replacement so with this custom package you're not breaking any dependencies.
   Ex:

7. Edit configuration files. There should be 3 EDITME configuration files for exim and one for eximon, one for each package that will be built. Copy one of the exim EDITME file to EDITME.exim4-$your_pkg_name then edit the new file to set up the new options you want.
   Ex:

8. pack the configuration files so your new configuration will be saved and used at build time:

9. Create the custom package. This is required only if you use a package name other then 'custom':

10. Activate the new package in debian/rules. Edit debian/rules and look for the line where the extradaemonpackages variable is defined and add your package name ( exim4-daemon-$my_pkg_name ) to the list of packages defined there.
11. Install build dependencies. You can skip this step if this is not the first time you build this package.

12. Build the packages:

13. Install the new package. if you already had some version of the exim4-daemon package installed you will have to remove it first and then you can install the custom package. The new package will be in the base directory created at step 1.
    Ex. (for amd64 etch exim 4.63-17 ) :

This process went pretty well for both exim 4.63 and 4.69 on lenny. Exim 4.63 only had experiemental support for domainkeys ( not dkim ) and exim 4.69 on lenny had support for both but I was only able to build it after applying a small patch to exim to make it work with the latest version of libdkim ( 1.0.19 ) .

This post was intended to be a general howto about building a custom exim package. I will write more details about actually building exim with domainkeys and/or dkim in a future post.