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Using supervise-daemon
Beginning with OpenRC-0.21 we have our own daemon supervisor, supervise-daemon., which can start a daemon and restart it if it terminates unexpectedly.
The following is a brief guide on using this capability.
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.
Daemons must not fork
Any deamon that you would like to have monitored by supervise-daemon must not fork. Instead, it must stay in the foreground. If the daemon itself forks, the supervisor will be unable to monitor it.
If the daemon can be configured to not fork, this should be done in the daemon's configuration file, or by adding a command line option that instructs it not to fork to the command_args_foreground variable shown below.
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=supervise-daemon
Several other variables affect the way services behave under supervise-daemon. They are documented on the openrc-run man page, but I will list them here for convenience:
pidfile=/pid/of/supervisor.pid
If you are using start-stop-daemon to monitor your scripts, the pidfile is the path to the pidfile the daemon creates. If, on the other hand, you are using supervise-daemon, this is the path to the pidfile the supervisor creates.
command_args_foreground should be used if the daemon you want to monitor forks and goes to the background by default. This should be set to the command line option that instructs the daemon to stay in the foreground.
This is very early support, so feel free to file bugs if you have issues.