Providers are a mechanism by which PlainBox can enumerate jobs and whitelists. Currently there are only v1 (as in version one) providers that basically have to behave as CheckBox itself (mini CheckBox forks for example)
There is ongoing work and discussion on V2 providers that would have a lower-level interface and would be able to define new job types, new whitelist types and generally all the next-gen semantics.
PlainBox does not come with any real provider by default. PlainBox sometimes creates special dummy providers that have particular data in them for testing.
The first (current) version of PlainBox providers has the following properties, this is also described by IProvider1:
* there is a directory with '.txt' or '.txt.in' files with RFC822-encoded
job definitions. The definitions need a particular set of keys to work.
* there is a directory with '.whitelist' files that contain a list (one per
line) of job definitions to execute.
* there is a directory with additional executables (added to PATH)
* there is a directory with an additional python3 libraries (added to
PYTHONPATH)