Ubuntu Manpage: finit — Fast init for Linux systems

NAME

     finit — Fast init for Linux systems

SYNOPSIS

     /sbin/finit [--] [debug] [finit.cond=foo[,bar[,baz]]] [finit.config=/path/to/alt/finit.conf]
                 [finit.debug] [finit.fstab=/etc/fstab.alt] [finit.status=<on,off>]
                 [finit.status_style=<classic,modern>] [loglevel=<0-7>] [panic=SEC] [quiet]
                 [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
     •  Process readiness notification for synchronizing system startup as well as
        reconfiguration at runtime.  Natively PID files are used, but systemd sd_notify() and s6
        notification is also supported.
     •  Limited support for tmpfiles.d(5), no aging, attributes, or subvolumes
     •  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

BOOTPARAM

finit support the following command line parameters to alter the behavior at boot. Notice
the -- separator needed to tell the kernel which paramters should be given to PID 1. For
more information on this, and available kernel command line options, see bootparam(7).

debug
Enable kernel debug. Debug messages are printed to the console until Finit
starts up, unless loglevel=7 (below) is used.

finit.cond=foo[,bar[,baz]]
set <boot/foo> condition, optionally multiple conditions can be set using the
same option, separated with a comma. Alternatively, multiple foo.cond=arg can be
given. Each will result in a <boot/arg> condition being set to control the rest
of the system bootstrap.

Very useful for selecting different boot modes, e.g. manufacturing test, firmware
upgrade, or rescue mode.

Note: <boot/...> conditions cannot be cleared with initctl!

finit.config=/path/to/alternative/finit.conf
override the compile-time bootstrap config file, default:

Useful when starting up in various rescue mode, factory, or production test
setups. Use the top-level configuration file directive rcsd /path/to/finit.d to
override the default rcS.d directory.

finit.debug
Enable Finit debug messages on system console and log. Sometimes useful when
doing board bringup. Before the system log daemon has started, Finit use the
kernel ring buffer, /dev/kmsg.

finit.fstab=/path/to/fstab.alt
Tell finit to use an alternate fstab to mount the file system from. Remember,
this file must be on the root=... file system provided to Finit from the kernel.
If this file is missing, finit falls back to its built-in default, which can be
changed at build time using the --with-fstab=/path/to/footab configure option.
It is even possible to completely disable the built-in using --without-fstab,
meaning finit must be started with the finit.fstab option.

Should finit discover that there is no fstab file available, including the
fallback, it triggers the same failure mode as when fsck fails, starting
sulogin(8), if that is availble. When sulogin is missing, or when the user exits
from sulogin, the system is rebooted.

Default fstab, unless changed at build-time: /etc/fstab

finit.status=<on,off>
Control finit boot progress, including banner. This used to be called
finit.show_status, which still works but is deprecated.

finit.status_style=<classic,modern>
Set Finit boot progress style, when enabled.

loglevel=<0-7>
set the kernel's log level, which is more granular than debug. Also, when
loglevel=7, Finit will not disable kernel logs to the console. This is very
useful when debugging the kernel at system bring-up. Since loglevel=7 is the
same as debug this means you have to use quiet for a quiet boot, until sysklogd
takes over logging of kernel events.

panic=SEC
By default the kernel does not reboot after a kernel panic. This setting will
cause a kernel reboot after SEC seconds.

quiet
Suppress kernel logging to console, except for warnings and errors. Also, see
loglevel and quiet above.

rescue | recover
Start rescue/maintenance mode. If your system comes with the bundled sulogin
program (Finit, or from util-linux/Busybox), you will be given a root login to a
maintenance shell. However, if sulogin is missing, the file
/lib/finit/rescue.conf is read and the system booted in a limited fallback mode.
See finit.conf(5) for more information.

single | S
Single user mode, runlevel 1, in Finit. Useful to debug problems with the
regular runlevel. All services and TTYs in [1] will be started, e.g., a tty [1]
@console nologin configuration presents you with a root console without login.

Note: by definition, single user mode does not have networking enabled. This is
also true for runlevel 1.

BOOTING

     Before laucnhing services, the system needs to be bootstrapped.  This involves mounting all
     filesystems (not already mounted by an initramfs) in /etc/fstab, or any alternate fstab file
     provided on the Finit command line using finit.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 based on the service declaration name:id, gives the condition
                    pid/name:id

           service  Tracks run/task/service state stansitions, including readiness.  E.g.,
                    service/foo/ready can be used as a condition for service bar, provided foo
                    properly signals its readiness to Finit.

           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

AUTHORS

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