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signals.md

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Finit Signals

Finit is often used on embedded and small Linux systems with BusyBox. Though Finit comes with its own tools for (poweroff, halt, reboot), for compatibility with the existing BusyBox toolset the following signals have been adopted:

  • SIGHUP
    Same effect as finit q, init q, or initctl reload, reloads all *.conf files in /etc/finit.d/

  • SIGUSR1
    Calls shutdown hooks, including HOOK_SHUTDOWN, stopping all running processes, and unmounts all file systems. Then tells kernel to halt. Most people these days want SIGUSR2 though.

    SysV init and systemd use this to re-open their FIFO/D-Bus.

  • SIGUSR2
    Like SIGUSR1, but tell kernel to power-off the system, if ACPI or similar exists to actually do this. If the kernel fails power-off, Finit falls back to halt.

    SysV init N/A, systemd dumps its internal state to log.

  • SIGTERM
    Like SIGUSR1, but tell kernel to reboot the system when done.

    SysV init N/A, systemd rexecutes itself.

  • SIGINT
    Sent from kernel when the CTRL-ALT-DEL key combo is pressed. SysV init and systemd default to reboot with shutdown -r.
    Finit currently forwards this to SIGTERM.

  • SIGPWR
    Sent from a power daemon, like powstatd(8), on changes to the UPS status. Traditionally SysV init read /etc/powerstatus and acted on "OK", "FAIL", or "LOW" and then removed the file.
    Finit currently forwards this to SIGUSR2.