service must be a directory.
runsv switches to the directory service and starts ./run. If ./run exits and ./finish exists, runsv starts ./finish. If ./finish doesn't exist or ./finish exits, runsv restarts ./run.
If ./run or ./finish exit immediately, runsv waits a second before starting ./finish or restarting ./run.
Two arguments are given to ./finish. The first one is ./run's exit code, or -1 if ./run didn't exit normally. The second one is the least significant byte of the exit status as determined by waitpid(2); for instance it is 0 if ./run exited normally, and the signal number if ./run was terminated by a signal. If runsv cannot start ./run for some reason, the exit code is 111 and the status is 0.
If the file service/down exists, runsv does not start ./run immediately. The control interface (see below) can be used to start the service and to give other commands to runsv.
If the directory service/log exists, runsv creates a pipe, redirects service/run's and service/finish's standard output to the pipe, switches to the directory service/log and starts ./run script. The standard input of the log service is redirected to read from the pipe.
runsv maintains status information in a binary format (compatible to the daemontools' supervise program) in service/supervise/status and service/log/supervise/status, and in a human-readable format in service/supervise/stat, service/log/supervise/stat, service/supervise/pid, service/log/supervise/pid.
The named pipes service/supervise/control, and (optionally) service/log/supervise/control are provided to give commands to runsv. You can use sv(8) to control the service or just write one of the following characters to the named pipe:
Up. If the service is not running, start it. If the service stops, restart it.
Down. If the service is running, send it a TERM signal, and then a CONT signal. If ./run exits, start ./finish if it exists. After it stops, do not restart service.
Once. If the service is not running, start it. Do not restart it if it stops.
Pause. If the service is running, send it a STOP signal.
Continue. If the service is running, send it a CONT signal.
Hangup. If the service is running, send it a HUP signal.
Alarm. If the service is running, send it a ALRM signal.
Interrupt. If the service is running, send it a INT signal.
Quit. If the service is running, send it a QUIT signal.
User-defined 1. If the service is running, send it a USR1 signal.
User-defined 2. If the service is running, send it a USR2 signal.
Terminate. If the service is running, send it a TERM signal.
Kill. If the service is running, send it a KILL signal.
Exit. If the service is running, send it a TERM signal, and then a CONT signal. Do not restart the service. If the service is down, and no log service exists, runsv exits. If the service is down and a log service exists, runsv closes the standard input of the log service, and waits for it to terminate. If the log service is down, runsv exits. This command is ignored if it is given to service/log/supervise/control.
Example: to send a TERM signal to the socklog-unix service, either do # sv term /etc/service/socklog-unix or # printf t >/etc/service/socklog-unix/supervise/control
printf(1) usually blocks if no runsv process is running in the service directory.
For each control character c sent to the control pipe, runsv first checks if service/control/c exists and is executable. If so, it starts service/control/c and waits for it to terminate, before interpreting the command. If the program exits with return code 0, runsv refrains from sending the service the corresponding signal. The command o is always considered as command u. On command d first service/control/t is checked, and then service/control/d. On command x first service/control/t is checked, and then service/control/x. The control of the optional log service cannot be customized.
If runsv receives a TERM signal, it acts as if the character x was written to the control pipe.
runsv exits 111 on an error on startup or if another runsv is running in service.
runsv exits 0 if it was told to exit.
Gerrit Pape <firstname.lastname@example.org>