Debian packaging against the rules

In a former post I talked about packaging your own software in the most convenient and natural way for the target audience. Think of a MSI or .exe installer for Microsoft Windows, distribution specific packages for Linux (maybe even by providing own repositories) or smartphone apps via the standard app stores. In the case of Debian packages there are quite strict rules about filesystem layout, licensing and signatures. This is all fine if you want to get your software upstream into official repositories.

If you are developing commercial software for specific clients things may be different! I suggest doing what serves the clients user experience (UX) best even in regard to packaging for debian or linux.

Packaging for your users

Packaging for Linux means you need to make sure that your dependencies and versioning are well defined. If you miss out here problems will arise in updating your software. Other things you may consider even if they are against the rules

  • Putting your whole application with executables, libraries, configuration and resources under the same prefix, e.g. /opt/${my_project} or /usr/local/${my_project}. That way the user finds everything in one place instead of scattered around in the file system.
    • On debian this has some implication like the need to use the conffiles-feature for your configuration
  • Package together what belongs together. Often times it has no real benefit to split headers, libraries, executables etc. into different packages. Fewer packages makes it easier for the clients to handle.
  • Provide integration with operating system facilities like systemd or the desktop. Such a seamless integration eases use and administration of your software as no “new tricks” have to be learned.
    • A simple way for systemd is a unit file that calls an executable with an environment file for configuration
  • Adjust the users path or put links to your executables in well known directories like /usr/bin. Running your software from the command line should be easy and with sensible defaults. Show sample usages to the user so they can apply “monkey see – monkey do”.

Example of a unit file:

[Unit]
Description=My Server

[Service]
EnvironmentFile=/opt/my_project/my-server.env
ExecStart=/usr/bin/my-server

[Install]
WantedBy=multi-user.target

In the environment file you can point to other configuration files like XML configs or the like if need be. Environment variables in general are a quite powerful way to customize behaviour of a program on a per-process base, so make sure your start scripts or executables support them for manual experimentation, too.

Possible additional preparations

If you plan to deliver your packages without providing an own repository and want to enable your clients to install them easily themselves you can further aid them.

If the target machines are few and can easily be prepared by you, install tools like gdebi that allow installation using double click and a graphical interface.

If the target machines are numerous implement automation with tools like ansible and ensure unattended installation/update procedures.

Point your clients to easy tools they are feeling comfortable with. That could of course be a command line utility like aptitude, too.

What to keep in mind

There is seldom a one-size-fits-all in custom software. Do what fits the project and your target audience best. Do not fear to break some rules if it improves the overall UX of your service.

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