Re: Configuration services

[Laurent Bercot <ska-supervision@skarnet.org>]

> Hi, does anyone use services that just set up some things but don't actually run a daemon?  This is hinted at http://smarden.org/pape/djb/daemontools/noinit.html.
> 
> Solaris does things like this with their SMF system and what they call "checkpoints".
> 
> I am doing this with runit by putting a while ./check; do; sleep 300; done; loop in the run script. Is there a better way?

 You can get rid of the shell for the 5 minutes of sleeping by letting
runit perform the loop itself. Your run script could look like:

#!/bin/sh
./check
exec sleep 300

or even better:

#!/command/execlineb -P
foreground { ./check }
sleep 300

 When sleep exits, the run script terminates, and runsv will automatically
start it again. No need for a loop inside your script. No need to keep the
shell around while the only thing to do is sleep.
 Additionally, you can decide to perform a ./check *now*, by sending a
SIGTERM to the service. (sv term)

 Bear in mind that all this is valid because you actually want to perform
an action regularly, which fits into the "service" model. (But if you are
using a crontab-like service on your system, you could also run your
regular check as a cron job or equivalent, and spare a service.)
 If you just want to set up some stuff *once*, and run no daemon, the
service model doesn't apply; write a script that does what you want and
just call it when needed (for instance at one-time system initialization),
don't try to keep it supervised.

-- 
 Laurent