[[!comment format=mdwn
 username="joey"
 subject="""comment 3"""
 date="2015-04-14T19:42:22Z"
 content="""
[period](http://hackage.haskell.org/package/propellor-2.2.1/docs/Propellor-Property-Scheduled.html)
is not a cron job, it just modifies the Property to only do anything
every so often.

It's also possible to modify a Property so it only runs once. 
[flagFile](http://hackage.haskell.org/package/propellor-2.2.1/docs/Propellor-Property.html#v:flagFile)
can be used to do that.

But there are good reasons for propellor to default to checking all
Properties of a system each time:

* It means that most Properties are idempotent, which has many good
  features, like being able to recover from a crash.
* If a system no longer has a configured Property, to fix it back to having
  the property it's supposed to have.
* Or, if it can't be fixed, to tell you with an error message in red.
* It keeps propellor mostly stateless; rather than having to record state
  about how it thinks a system is, which could diverge from reality,
  it just looks at how it actually is.
"""]]
