Propellor is a single system, but it's made up of some logically separate components.

• Propellor is a Haskell library. The library can be installed from hackage in the usual ways. It complies with the Haskell Package Version Policy.
• ~/.propellor/ is a git repository, which contains at least your config.hs file and a cabal file. This gets deployed to each machine you manage with propellor, where it's installed as /usr/local/propellor/
• There can also be a propellor command in your PATH. If you apt-get install propellor, you'll get one installed, or cabal install propellor will put the command in ~/.cabal/bin/propellor. This propellor command is just a wrapper; it builds and runs what you have set up in ~/.propellor/

full .propellor repository

Typically, the ~/.propellor/ git repository is set up by running the propellor command, or by ?cloning propellor. That makes the repository contain the full source code to propellor, including the Haskell library.

So if you want to, you can edit any part of Propellor's source code. Don't like how a property works, or need to make it more general? Just edit then copy in ~/.propellor/src/Propellor/ and it will be used. See contributing if you want to send your improvements back.

minimal .propellor repository

All that really needs to be in ~/.propellor/ though, is a config.hs file, and a cabal file. Running propellor when ~/.propellor/ doesn't exist will ask you if you want a minimal config, and create those files.

In this configuration, when propellor is deploying itself to a new host, it will automatically install the version of the propellor library specified in the cabal file.