openrc/s6-guide.md

# Using S6 with OpenRC

Beginning with OpenRC-0.16, we support using the s6 supervision suite
from Skarmet Software in place of start-stop-daemon for monitoring
daemons [1].

## Setup

Documenting s6 in detail is beyond the scope of this guide. It will
document how to set up OpenRC services to communicate with s6.

### Use Default start, stop and status functions

If you write your own start, stop and status functions in your service
script, none of this will work. You must allow OpenRC to use the default
functions.

### Dependencies

All OpenRC service scripts that want their daemons monitored by s6
should have the following line added to their dependencies to make sure
the s6 scan directory is being monitored.

need s6-svscan

### Variable Settings

The most important setting is the supervisor variable. At the top of
your service script, you should set this variable as follows:

supervisor=s6

Several other variables affect s6 services. They are documented on the
openrc-run man page, but I will list them here for convenience:

s6_service_path - the path to the s6 service directory
s6_svwait_options_start - the options to pass to s6-svwait when starting
s6_svwait_options_stop - the options to pass to s6-svwait when stopping.

The s6_service_path variable defaults to /var/svc.d/${RC_SVCNAME} if it
is not set in the service script. For example, if you want a service
script called /etc/init.d/foobar to use s6 to monitor its daemon, the s6
service should be the directory /var/svc.d/foobar.

See the documentation for s6 for more information about s6 service
directories.

The s6_svwait_options_* variables set command line options to pass to
s6-svwait when starting or stopping the s6 service. These can be very
useful for waiting for s6 services to signal when they are up, timing out
when an s6 service doesn't come up, etc.

This is very early support, so feel free to file bugs if you have
issues.

[1] https://www.skarnet.org/software/s6