66-scanctl.md

title: The 66 Suite: 66-scanctl author: Eric Vidal eric@obarun.org

66

Software

obarun.org

66-scanctl

Sends a signal to a scandir. Safe wrapper around s6‑svscanctl.

Interface

    66-scanctl [ -h ] [ -z ] [ -v verbosity ] [ -l live ] [ -d notif ] [ -t rescan ] [ -e environment ] [ -o owner ] start|stop|reload|quit|nuke|zombies or any s6-svscanctl options.

This program sends a signal to an already running scandir at live where by default live is at %%livedir%% or the resulting path provided by the ‑l option. If owner is not explicitely set with ‑o then the user of the current process will be used instead.

Exit codes

• 0 success
• 100 wrong usage
• 111 system call failed

Options

• -h : prints this help.

• -z : use color.

• -v verbosity : increases/decreases the verbosity of the command.

  • 1 : only print error messages. This is the default.
  • 2 : also print warning messages.
  • 3 : also print tracing messages.
  • 4 : also print debugging messages.

• -l live : changes the supervision directory of service to live. By default this will be %%livedir%%. The default can also be changed at compile time by passing the --livedir=live option to ./configure. An existing absolute path is expected and should be within a writable and executable filesystem - likely a RAM filesystem—see 66-scandir.

• -d notif : notify readiness on file descriptor notif. When scandir is ready to accept commands from 66‑scanctl, it will write a newline to notif. notif cannot be lesser than 3. By default, no notification is sent. If -b is set, this option have no effects.

• -t rescan : perform a scan every rescan milliseconds. If rescan is set to 0 (the default), automatic scans are never performed after the first one and s6‑svscan will only detect new services by issuing either 66‑scanctl reload or s6‑svscanctl -a. It is strongly discouraged to set rescan to a positive value under 500.

• -e environment : an absolute path. Merge the current environment variables with variables found in this directory before starting the scandir. Any file in environment not beginning with a dot and not containing the = character will be read and parsed.

• -o owner : send the signal to a scandir owned by owner instead of the current owner of the process. owner needs adecuate permissions to deal with the scandir.

Signal

Any signal accepted by s6‑svscanctl can be passed but without the dash ‑ character. As a result if you wanted to send a ‑t signal, you need to use: 66‑scanctl t. Further a series of commands is also accepted in the same way: 66‑scanctl st. A few convenient keywords were added to avoid having to remember basic and useful commands:

• reload = ‑an
• interrupt = ‑i
• quit = ‑q
• halt = ‑0
• reboot = ‑6
• poweroff = ‑7

Usage examples

    66-scanctl reload

Updates the process supervision tree to exactly match the services listed in scandir. This command is strictly equal to:

    s6-svscanctl -an /path_to_scandir

s6‑svscan.