NAME

     finit — Fast init for Linux systems

SYNOPSIS

     /sbin/finit [finit.status_style=classic] [finit.show_status=[on,off]] [finit.debug]
                 [rescue | recover] [single | S]
     /sbin/telinit [-hv] [q | Q | 0-9]

DESCRIPTION

     Fast init for Linux systems.  Reverse engineered from the EeePC fastinit, 10+ years ago by
     Claudio Matsuoka, "gaps filled with frog DNA ...".  Focus is on small and embedded systems,
     although Finit is fully usable on server and desktop systems as well.

     Features include:
     •  Runlevels, defined per service
     •  One-shot tasks, services (daemons), or SysV init start/stop scripts
     •  Runparts and /etc/rc.local support
     •  Process supervision similar to systemd(8)
     •  Sourcing environment files
     •  Conditions for network/process/custom dependencies
     •  Pre/Post script actions
     •  Tooling to enable/disable services
     •  Built-in getty
     •  Built-in watchdog, with support for hand-over to watchdogd:
        https://troglobit.com/watchdogd.html
     •  Built-in support for Debian/BusyBox /etc/network/interfaces
     •  Cgroups v2, both configuration and monitoring in `initctl top`
     •  Plugin support for customization
     •  Proper rescue mode with bundled `sulogin` for protected maintenance shell

BOOTING

     Before laucnhing services, the system needs to be bootstrapped.  This involves mounting all
     filesystems (not already mounted by an initramfs) in /etc/fstab, ensuring that necessary
     filesystems like: /dev, /proc, /sys, and /run are available and can provide the system with
     the services required.

     With that out of the way, a set of plugins take over:

           bootmisc.so  Cleans up stale files from previous boots and default directories are
                        created in tmpfs filesystems

           modprobe.so  Probes kernel modules required by the system

           procps.so    Set kernel variables from /etc/sysctl.conf et al

     When the plugins are done, finit reads /etc/finit.conf and all other enabled services in
     /etc/finit.d/*.  First all services, run/tasks in runlevel S (bootStrap) are started, When
     all run/tasks have completed, Finit changes to the configured runlevel (default 2),
     Processes are started in parallel, in dependency order according to their conditions.

     When all services and run/tasks have been started, the console progress is disabled and all
     configured getty services are started.

CONDITIONS

     The condition subysystem in Finit was initially created to track PID files of daemons.  If
     service/task B requires service A to have started, Finit waits for the PID file of service A
     to be created/updated before it starts service B.  Conversely, if service A is stopped and
     its PID file removed, service B is also stopped.

     The following condition families are available today:

           net  Linux netlink events, e.g. net/route/default, net/eth0/up, and net/et0/running

           pid  PID files basd on the service declaration name:id, gives the condition
                pid/name:id

           sys  System conditions, e.g. sys/key/ctrlaltdel and sys/pwr/fail

           usr  User conditions, assert and deassert using initctl cond [set|clr] foo

SIGNALS

     PID 1 is the only process that by default blocks all signals.  Finit allows for the
     following signals to control operation, but recommends instead using the initctl(8) tool.

     HUP   Tell finit to reload its configuration file(s), same as initctl reload

     USR1  Restart API (initctl) socket.

     USR2  Tell finit to perform a system shutdown, same as initctl poweroff

     TERM  Like SIGUSR2 but performs a reboot, same as initctl reboot

     INT   Sent from kernel when Ctrl-Alt-Del is pressed (on the console), this asserts the
           sys/key/ctrlaltdel condition, which can be used to start tasks or services

     PWR   Sent from a a power daemon on changes to UPS status, Finit asserts the sys/pwr/fail
           condition

FILES

     /etc/finit.conf                Main configuration file
     /etc/finit.d/*.conf            Static service definitions
     /etc/finit.d/available/*.conf  Available services
     /etc/finit.d/enabled/*.conf    Symlinks from available
     /run/finit/                    Runtime files, including the condition subsystem

SEE ALSO

     finit.conf(5) initctl(8)

AUTHORS

     finit was conceived and reverse engineered by Claudio Matsuoka.  Since v1.0, maintained by
     Joachim Wiberg, with contributions by many others.