[[!comment format=mdwn username="joey" subject="""comment 1""" date="2015-04-19T16:07:24Z" content=""" Propellor makes it very easy to put together a property like this. Let's start with a property that combines the two properties you mentioned: hasLoginShell :: UserName -> FilePath -> Property hasLoginShell user shell = shellSetTo user shell `requires` shellEnabled shell The shellEnabled property can be easily written using propellor's file manipulation properties. -- Need to add an import to the top of the source file. import qualified Propellor.Property.File as File shellEnabled :: FilePath -> Property shellEnabled shell = "/etc/shells" `File.containsLine` shell And then, we want to actually change the user's shell. The `chsh(1)` program can do that, so we can simply tell propellor the command line to run: shellSetTo :: UserName -> FilePath -> Property shellSetTo user shell = cmdProperty "chsh" ["--shell", shell, user] The only remaining problem with this is that shellSetTo runs chsh every time, and propellor will always display that it's made a change each time it runs, even when it didn't really do much. Now, there's an easy way to avoid that problem, we could just tell propellor that it's a trivial property, and then it will run chsh every time and not think it made any change: shellSetTo :: UserName -> FilePath -> Property shellSetTo user shell = trivial $ cmdProperty "chsh" ["--shell", shell, user] But, it's not much harder to do this right. Let's make the property check if the user's shell is already set to the desired value and avoid doing anything in that case. shellSetTo :: UserName -> FilePath -> Property shellSetTo user shell = check needchangeshell $ cmdProperty "chsh" ["--shell", shell, user] where needchangeshell = do currshell <- userShell <$> getUserEntryForName user return (currshell /= shell) And that will probably all work, although I've not tested it. You might want to throw in some uses of `describe` to give the new properties more useful descriptions. I hope this has been helpful as an explanation of how to add properties to Propellor, and if you get these properties to work, a patch adding them to Propellor.User would be happily merged. """]]