On Fri, Mar 13, 2015 at 05:30:27PM +0100, Kurt Roeckx wrote:
> I've been looking for documentation about what the various
> services in master.cf do. I can't seem to find any documentation
> for that. I can guess what a few of those do because the command
> they run is documented. But it's not always clear what it means
> exactly.
There are lots of internal services that you simply need to run:
qmgr unix n - n 300 1 qmgr
rewrite unix - - n - - trivial-rewrite
pickup unix n - n 60 1 pickup
cleanup unix n - n - 0 cleanup
bounce unix - - n - 0 bounce
defer unix - - n - 0 bounce
trace unix - - n - 0 bounce
verify unix - - n - 1 verify
flush unix n - n 1000? 0 flush
showq unix n - n - - showq
anvil unix - - n - 1 anvil
scache unix - - n - 1 scache
proxymap unix - - n - - proxymap
proxywrite unix - - n - 1 proxymap
# Required for TLS support
tlsmgr unix - - n 1000? 1 tlsmgr
Without the above various core features don't work. Then there
the delivery agents that implement Postfix transports:
local unix - n n - - local
virtual unix - n n - - virtual
smtp unix - - n - - smtp
relay unix - - n - - smtp
lmtp unix - - n - - lmtp
error unix - - n - - error
retry unix - - n - - error
discard unix - - n - - discard
You can create as many clones of these as you like, and/or disable
those you don't need.
Then there are the built-in inet services, smtpd(8), postscreen(8)
or qmqpd(8). These can be cloned to create custom TCP service
endpoints. Most common:
smtp inet n - n - - smtpd
You can build new transports with the pipe(8) delivery agent.
And spawn(8) can be used to run ad-hoc programs in response to
incoming connections.
> From examples I've seen, it seems you can create your own
> services, but it's unclear to me how those get "created", and when
> they get used.
You can create your transports, including pipe(8) transports.
You can create custom cleanup services.
You can create clones of SMTP inet listeners.
You can spawn(8) third-party SMTP proxies or policy services.
Transports get used when you route email to them via the
transport table or equivalent. Inet services get used when
someone connects to them from outside.
Custom cleanup services get used by an smtpd(8) or other service
that injects mail into the queue and is configured with a "-o
cleanup_service_name" override.
--
Viktor.
