propellor: property-based host configuration management in haskell

[ bsd2, library, program, utility ] [ Propose Tags ]

Propellor enures that the system it's run in satisfies a list of properties, taking action as necessary when a property is not yet met.

It is configured using haskell.

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Change log CHANGELOG
Dependencies ansi-terminal, async, base (>=4.5 && <5), bytestring, containers, directory, filepath, hslogger, IfElse, MissingH, network, process, unix, unix-compat [details]
License LicenseRef-GPL
Copyright 2014 Joey Hess
Author Joey Hess
Maintainer Joey Hess <>
Category Utility
Home page
Source repo head: git clone git://
Uploaded by JoeyHess at 2014-04-03T05:59:39Z
Distributions Debian:5.5.0, NixOS:5.10.2
Executables config, propellor
Downloads 67849 total (1210 in the last 30 days)
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Status Hackage Matrix CI
Docs available [build log]
Successful builds reported [all 1 reports]




Maintainer's Corner

For package maintainers and hackage trustees

Readme for propellor-0.2.1

[back to package description]

This is a configuration management system using Haskell and Git.

Propellor enures that the system it's run against satisfies a list of properties, taking action as necessary when a property is not yet met.

Propellor is configured via a git repository, which typically lives in ~/.propellor/. The git repository contains a config.hs file, and also the entire source code to propellor.

You typically want to have the repository checked out on a laptop, in order to make changes and push them out to hosts. Each host will also have a clone of the repository, and in that clone "make" can be used to build and run propellor. This can be done by a cron job (which propellor can set up), or a remote host can be triggered to update by running propellor on your laptop: propellor --spin $host

Properties are defined using Haskell. Edit config.hs to get started. For API documentation, see

There is no special language as used in puppet, chef, ansible, etc.. just the full power of Haskell. Hopefully that power can be put to good use in making declarative properties that are powerful, nicely idempotent, and easy to adapt to a system's special needs.

Also avoided is any form of node classification. Ie, which hosts are part of which classes and share which configuration. It might be nice to use reclass[1], but then again a host is configured using simply haskell code, and so it's easy to factor out things like classes of hosts as desired.

quick start

  1. Get propellor installed cabal install propellor or apt-get install propellor

  2. Run propellor for the first time. It will set up a ~/.propellor/ git repository for you.

  3. In ~/.propellor/, use git to push the repository to a central server (github, or your own git server). Configure that central server as the origin remote of the repository.

  4. If you don't have a gpg private key, generate one: gpg --gen-key

  5. Run: propellor --add-key $KEYID

  6. Edit ~/.propellor/config.hs, and add a host you want to manage. You can start by not adding any properties, or only a few.

  7. Pick a host and run: propellor --spin $HOST

  8. Now you have a simple propellor deployment, but it doesn't do much to the host yet, besides installing propellor.

    So, edit ~/.propellor/config.hs to configure the host (maybe start with a few simple properties), and re-run step 7. Repeat until happy and move on to the next host. :)

  9. To move beyond manually running propellor --spin against hosts when you change configuration, add a property to your hosts like: Cron.runPropellor "30 * * * *"

    Now they'll automatically update every 30 minutes, and you can git commit -S and git push changes that affect any number of hosts.

  10. Write some neat new properties and send patches to!


Propellor's security model is that the hosts it's used to deploy are untrusted, and that the central git repository server is untrusted.

The only trusted machine is the laptop where you run propellor --spin to connect to a remote host. And that one only because you have a ssh key or login password to the host.

Since the hosts propellor deploys are not trusted by the central git repository, they have to use git:// or http:// to pull from the central git repository, rather than ssh://.

So, to avoid a MITM attack, propellor checks that any commit it fetched from origin is gpg signed by a trusted gpg key, and refuses to deploy it otherwise.

That is only done when privdata/keyring.gpg exists. To set it up:

gpg --gen-key                 # only if you don't already have a gpg key
propellor --add-key $MYKEYID

In order to be secure from the beginning, when propellor --spin is used to bootstrap propellor on a new host, it transfers the local git repositry to the remote host over ssh. After that, the remote host knows the gpg key, and will use it to verify git fetches.

Since the propoellor git repository is public, you can't store in cleartext private data such as passwords, ssh private keys, etc.

Instead, propellor --spin $host looks for a ~/.propellor/privdata/$host.gpg file and if found decrypts it and sends it to the remote host using ssh. This lets a remote host know its own private data, without seeing all the rest.

To securely store private data, use: propellor --set $host $field The field name will be something like 'Password "root"'; see PrivData.hs for available fields.


Set PROPELLOR_DEBUG=1 to make propellor print out all the commands it runs and any other debug messages that Properties choose to emit.