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66-svctl

Low-level control primitive: writes raw command bytes directly to a service's supervise/control fifo.

Interface

66-svctl [ -h ] [ -w uUdDrR ] [ -T milliseconds ] [ -s signal ] [ -abqHkti12pcylrodDuUxOQ ] [ --stop-group | --cont-group | --kill-group ] servicedir...

This program sends one or more commands to the 66-supervise process that monitors a service. It operates directly on a service directory: it reads nothing — no resolve database, no service name resolution, no state — it just opens servicedir/supervise/control and writes the requested bytes.

This is the reason it exists: it is the recovery path when the resolve database is unusable (a corrupted resolve makes 66 stop foo unable to map the name, but the control fifo still answers), and the primitive the system scripts rely on. It is installed in the libexec directory and is not meant for everyday use — the friendly, resolve-aware path is 66 signal, which also handles dependencies and accepts service names.

Several servicedir can be given, separated by a space. Commands accumulate in the order they appear on the command line (clustering works: -dx writes d then x). If a command cannot be sent to a servicedir, an error is reported and the remaining directories are still processed; the exit code reflects the last failure.

Unless -w is given, 66-svctl writes the commands and exits immediately without waiting for the service to reach any particular state.

Options

  • -h, --help: print this help.
  • -w, --wait uUdDrR: do not exit until the service reaches the wanted state. The accepted values are the same as 66 signal: u up, U up and ready (notified), d down, D down and ready to be brought up, r (re)started, R (re)started and ready. The wait is performed through the native event mechanism on servicedir/event and stays resolve-independent. If the service declares no readiness notification (no Notify set), a readiness wait (U/D/R) is downgraded to its non-ready equivalent (u/d/r).
  • -T, --timeout milliseconds: with -w, fail after this delay if the wanted state has not been reached. 0 (the default) waits forever.
  • -s, --signal signal: send a signal to the supervised process by signal name or number, restricted to the user-available signals listed below.
  • -a, --alarm: send a SIGALRM signal.
  • -b, --abort: send a SIGABRT signal.
  • -q, --quit: send a SIGQUIT signal.
  • -H, --hangup: send a SIGHUP signal.
  • -k, --kill: send a SIGKILL signal.
  • -t, --term: send a SIGTERM signal.
  • -i, --interrupt: send a SIGINT signal.
  • -1, --usr1: send a SIGUSR1 signal.
  • -2, --usr2: send a SIGUSR2 signal.
  • -p, --stop: send a SIGSTOP signal.
  • -c, --cont: send a SIGCONT signal.
  • -y, --winch: send a SIGWINCH signal.
  • --stop-group: send a SIGSTOP signal to the whole process group of the supervised process.
  • --cont-group: send a SIGCONT signal to the whole process group of the supervised process.
  • --kill-group: send a SIGKILL signal to the whole process group of the supervised process.
  • -r, --restart: if the service is up, restart it by sending it a signal (default SIGTERM).
  • -l, --reload: if the service is up, reload it by sending it a signal (default SIGHUP).
  • -o, --once: once. Equivalent to -uO.
  • -d, --down: bring the service down (SIGTERM then SIGCONT) and do not restart it.
  • -D, --down-keep: bring the service down and create a down file so it is not brought up automatically.
  • -u, --up: bring the service up.
  • -U, --up-restart: bring the service up and remove any down file so it can be restarted automatically.
  • -x, --exit: bring the service down and tell its supervisor to exit once it is down.
  • -O, --once-at-most: mark the service to run once at most (do not restart it when it dies).
  • -Q, --once-at-most-down: once at most, and bring the service down.

Usage examples

Bring the service whose directory is /run/66/scandir/0/foo down

66-svctl -d -- /run/66/scandir/0/foo

Bring it up and block until it has notified readiness, giving up after 5 seconds

66-svctl -u -w U -T 5000 -- /run/66/scandir/0/foo

Bring it down and let its supervisor exit

66-svctl -dx -- /run/66/scandir/0/foo