.\"                                      Hey, EMACS: -*- nroff -*-
.\" First parameter, NAME, should be all caps
.\" Second parameter, SECTION, should be 1-8, maybe w/ subsection
.\" other parameters are allowed: see man(7), man(1)
.Dd June 6, 2021
.\" Please adjust this date whenever revising the manpage.
.Dt FINIT 8 SMM
.Os Linux
.Sh NAME
.Nm finit
.Nd Fast init for Linux systems
.Sh SYNOPSIS
.Nm /sbin/finit
.Op finit.status_style=classic
.Op finit.show_status=[on,off]
.Op finit.debug
.Op rescue | recover
.Op single | S
.Nm /sbin/telinit
.Op Fl hv
.Op q | Q | 0-9
.Sh 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.
.Pp
Features include:
.Bl -bullet -width 1n -compact
.It
Runlevels, defined per service
.It
One-shot tasks, services (daemons), or SysV init start/stop scripts
.It
Runparts and
.Pa /etc/rc.local
support
.It
Process supervision similar to
.Xr systemd 8
.It
Sourcing environment files
.It
Conditions for network/process/custom dependencies
.It
Pre/Post script actions
.It
Tooling to enable/disable services
.It
Built-in getty
.It
Built-in watchdog, with support for hand-over to
.Lk https://troglobit.com/watchdogd.html watchdogd
.It
Built-in support for Debian/BusyBox
.Pa /etc/network/interfaces
.It
Cgroups v2, both configuration and monitoring in `initctl top`
.It
Plugin support for customization
.It
Proper rescue mode with bundled `sulogin` for protected maintenance shell
.El
.Sh BOOTING
.Pp
Before laucnhing services, the system needs to be bootstrapped.  This
involves mounting all filesystems (not already mounted by an initramfs)
in
.Pa /etc/fstab ,
ensuring that necessary filesystems like:
.Pa /dev ,
.Pa /proc ,
.Pa /sys ,
and
.Pa /run
are available and can provide the system with the services required.
.Pp
With that out of the way, a set of plugins take over:
.Pp
.Bl -tag -width bootmisc.so -offset indent
.It Cm bootmisc.so
Cleans up stale files from previous boots and default directories are
created in tmpfs filesystems
.It Cm modprobe.so
Probes kernel modules required by the system
.It Cm procps.so
Set kernel variables from
.Pa /etc/sysctl.conf
et al
.El
.Pp
When the plugins are done, finit reads
.Pa /etc/finit.conf
and all other enabled services in
.Pa /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.
.Pp
When all services and run/tasks have been started, the console progress
is disabled and all configured getty services are started.
.Sh 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.
.Pp
The following condition families are available today:
.Pp
.Bl -tag -width pid -offset indent
.It Cm net
Linux netlink events, e.g. net/route/default, net/eth0/up, and
net/et0/running
.It Cm pid
PID files basd on the service declaration
.Cm name:id ,
gives the condition pid/name:id
.It Cm sys
System conditions, e.g. sys/key/ctrlaltdel and sys/pwr/fail
.It Cm usr
User conditions, assert and deassert using
.Cm initctl cond [set|clr] foo
.El
.Sh 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
.Xr initctl 8
tool.
.Pp
.Bl -tag -width TERM
.It HUP
Tell
.Nm
to reload its configuration file(s), same as
.Cm initctl reload
.It USR1
Restart API
.Cm ( initctl )
socket.
.It USR2
Tell
.Nm
to perform a system shutdown, same as
.Cm initctl poweroff
.It TERM
Like SIGUSR2 but performs a reboot, same as
.Cm initctl reboot
.It 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
.It PWR
Sent from a a power daemon on changes to UPS status, Finit asserts
the sys/pwr/fail condition
.El
.Sh FILES
.Bl -tag -width /etc/finit.d/available/*.conf -compact
.It Pa /etc/finit.conf
Main configuration file
.It Pa /etc/finit.d/*.conf
Static service definitions
.It Pa /etc/finit.d/available/*.conf
Available services
.It Pa /etc/finit.d/enabled/*.conf
Symlinks from available
.It Pa /run/finit/
Runtime files, including the condition subsystem
.El
.Sh SEE ALSO
.Xr finit.conf 5
.Xr initctl 8
.Sh AUTHORS
.Nm
was conceived and reverse engineered by Claudio Matsuoka.  Since v1.0,
maintained by Joachim Wiberg, with contributions by many others.