The s6-svscanctl program

s6-svscanctl sends commands to a running s6-svscan process.

Interface

     s6-svscanctl [ -phratszbnNiq0678 ] svscandir

s6-svscanctl sends the given series of commands to the s6-svscan process monitoring the svscandir directory, then exits 0. It exits 111 if it cannot send a command, or 100 if no s6-svscan process is running on svscandir.

Options

-p : poweroff mode. s6-svscan will exec into ./.s6-svscan/finish poweroff when it is told to terminate.
-h : Hangup. s6-svscan will send a SIGHUP to all the maintained s6-supervise processes, then run its finish procedure.
-r : reboot mode. s6-svscan will exec into ./.s6-svscan/finish reboot when it is told to terminate. This is s6-svscan's default mode.
-a : Alarm. s6-svscan will immediately perform a scan of svscandir to check for services.
-t : Terminate. s6-svscan will send a SIGTERM to all the s6-supervise processes supervising a service and a SIGHUP to all the s6-supervise processes supervising a logger, then run its finish procedure.
-s : halt mode. s6-svscan will exec into ./.s6-svscan/finish halt when it is told to terminate.
-z : destroy zombies. Immediately triggers s6-svscan's reaper mechanism.
-b : abort. s6-svscan will exec into its finishing procedure. It will not kill any of the maintained s6-supervise processes.
-n : nuke. s6-svscan will kill all the s6-supervise processes it has launched but that did not match a service directory last time svscandir was scanned, i.e. it prunes the supervision tree so that it matches exactly what was in svscandir at the time of the last scan. A SIGTERM is sent to the s6-supervise processes supervising services and a SIGHUP is sent to the s6-supervise processes supervising loggers.
-N : Really nuke. Does the same thing as -n, except that SIGTERM is sent to all the relevant s6-supervise processes, even if they are supervising loggers. That means that the logger processes will be killed with a SIGTERM instead of being allowed to exit at their own pace.
-i : Interrupt. Equivalent to -rt : s6-svscan will terminate in reboot mode.
-q : Quit. s6-svscan will send all its s6-supervise processes a SIGTERM, then exec into its finish procedure.
-0 : Halt. Equivalent to -st : s6-svscan will terminate in halt mode.
-6 : Reboot. Equivalent to -i.
-7 : Poweroff. Equivalent to -pt: s6-svscan will terminate in poweroff mode.
-8 : Other. s6-svscan will terminate in "other" mode.

Usage examples

 s6-svscanctl -an /service

Updates the process supervision tree to exactly match the services listed in /service.

 s6-svscanctl -6 /service

Orders the s6-svscan process monitoring /service to exit in reboot mode: all the supervision tree at /service will be terminated, and s6-svscan will execute into the /service/.s6-svscan/finish script with the reboot argument.

Internals

s6-svscanctl writes control commands into the svscandir/.s6-svscan/control FIFO. An s6-svscan process running on svscandir will be listening to this FIFO, and will read and interpret those commands.