runit’s service supervision resolves dependencies automatically for many or even most service daemons, those that exit if another service they need to function properly is not or no longer available. The runsv supervisor will then start them again, until everything is in shape.
For service daemons with different behavior, or to arrange services more structurally, the sv program can help. A few examples:
For the service daemon floyd, that needs the pinkd
service up and running, add sv start pinkd to
floyd’s run script, right after
set -e.
#!/bin/sh
set -e
sv start pinkd
exec floydWhen the pinkd service daemon crashes or is restarted for
some other reason and the floyd daemon is unable to handle
this, add sv hup floyd (or whatever the floyd
daemon understands) to pinkd’s finish script to
force its reload or restart.
#!/bin/sh
sv hup floydIf the pinkd service shall be stopped when the
floyd service is stopped gracefully, add
test "$1" != 0 || sv down pinkd to floyd’s
finish script.
#!/bin/sh
test "$1" != 0 || sv down pinkdOr vice versa.
Explore the sv program for more options.
For service daemons that do not make their service available
immediately after starting, a check program can be added.
The sv program will
use this check program to better evaluate whether a service
is fully started and available, for example:
For a mail service listening on localhost:25, this check
program could be used
#!/bin/sh
exec nc -z localhost 25