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.

Linux                                             June 6, 2021                                          FINIT(8)