==============================================================================
                      Finit | Fast Init Replacement
==============================================================================
|cistatus|

Finit is a small `SysV init`_ replacement with `process supervision`_
similar to that of `daemontools`_ and `runit`_.  Its focus is on small
and embedded GNU/Linux systems, although fully functional on standard
server and desktop installations.  It should also work on other UNIX
systems, but this has yet to be proven.

Finit is fast because it starts services in parallel, it then supervises
and automatically restarts them if they fail.  This can be extended upon
with custom callbacks for all services, hooks into the boot process, or
plugins to extend the functionality and adapt Finit to your needs.

Finit is not only fast, it's arguably one of the easiest to get started
with.  A complete system can be booted with one simple configuration
file, ``/etc/finit.conf``, see below for syntax.


Features
--------

**Process Supervision**
Start, monitor and restarting services if they fail.

**Runlevels**
Finit supports standard runlevels if you want, but you don't need them
for simple installations.

**Plugins**
Extend and modify finit behavior.  See examples in plugins/ directory.
Plugin capabilities:
   
* Service callbacks — modify service arguments, run/restart/stop
* Task/Run callbacks — a one-shot commands, executed in sequence
* Hooks — hook into the boot at predefined points to extend finit
* I/O — listen to external events and control finit behavior/services

Extensions and functionality not purely related to what an /sbin/init
needs to start a system are available as a set of plugins that either
hook into the boot process or respond to various I/O.


/etc/finit.conf
---------------

Contrary to most script based init alternatives (`SysV init`_, upstart_,
systemd_, OpenRC_ and the likes) finit instead reads its configuration
from ``/etc/finit.conf``.  Below is a brief list, see the source code
for the full list:

check <DEV>
    Run fsck on a file system before mounting it

module <MODULE>
    Load a kernel module, with optional arguments

network <PATH>
    Script or program to bring up networking, with optional arguments

runlevel <N>
    N is the runlevel number 1-9, where 6 is reserved for reboot

run [RUN_LVLS] /path/to/cmd ARGS -- Optional description
    One-shot command to run in sequence when entering a runlevel, with
    optional arguments and description.  This command is guaranteed to
    be completed before running the next command.

task [RUN_LVLS] /path/to/cmd ARGS -- Optional description
    One-shot like 'run', but starts in parallel with the next command

service [RUN_LVLS] /path/to/daemon ARGS -- Optional description
    Service, or daemon, to be monitored and automatically restarted if
    it exits prematurely.  Please note that you often need to provide
    a --foreground or --no-background argument to most daemons to
    prevent them from forking off to the background.

runparts <PATH>
    Call run-parts(8) on a directory other than default ``/etc/finit.d``

include <CONF>
    Include another configuration file, ``/etc/finit.d``, or runparts
    path is prepended to file if the file is not found or an absolute
    path is not given

tty [RUN_LVLS] <DEV | /bin/sh>
    Start a getty on the given TTY device, in the given runlevels.  When
    no tty setting is given in ``finit.conf``, or if /bin/sh is given as
    argument instead of a device path, a single shell is started on the
    default console.  Useful for really bare-bones systems

console <DEV>
    Some embedded systems have a dedicated console port. This command
    tells finit to not start getty, but instead print a friendly message
    and wait for the user to activate the console with a key press before
    starting getty.

When running ``make install`` no default ``/etc/finit.conf`` will be
provided since the system requirements differ too much.  Try out the
Debian 6.0 example ``/usr/share/doc/finit/finit.conf`` configuration
that is capable of service monitoring SSH, sysklogd, gdm and a console
getty!


/etc/finit.d
------------

At the end of the boot, when networking and all services are up, finit
calls its built-in run-parts(8) on the ``/etc/finit.d/`` directory, if
it exists.  Similar to how the ``/ec/rc.local`` file works in most other
init daemons, only finit runs a directory of scripts.  This replaces the
earlier support for a ``/usr/sbin/services.sh`` script in the original
finit.


Runlevels
---------

Support for runlevels_ is included in Finit from v1.8.  By default all
services, tasks, run commands and TTYs listed without a set of runlevels
get a default set [234] assigned.  The default runlevel after boot is 2.

To specify an allowed set of runlevels for a service, run command, task,
or tty, add [NNN] to it in finit.conf, like this::

  run     [S]      /etc/init.d/acpid start -- Starting ACPI Daemon
  task    [S]      /etc/init.d/kbd start -- Preparing console
  service [S12345] /sbin/klogd -n -x -- Kernel log daemon
  tty     [12345]  /dev/tty1
  tty     [2]      /dev/tty2
  tty     [2]      /dev/tty3
  tty     [2]      /dev/tty4
  tty     [2]      /dev/tty5
  tty     [2]      /dev/tty6

In this example acpid is started once at bootstrap using a conventional
SysV init script.  Here the run command was used, meaning the following
task command is not run until the init script has fully completed.

Tasks and services are started in parallel, while run commands are run
in the order listed and subsequent commands are not started until a run
command has completed.

Existing finit.conf files that lack runlevel setting will get a default
runlevel assigned, [234].

Switching between runlevels can be done by calling init with a single
argument, e.g., 'init 5' switches to runlevel 5.


Rebooting and Halting
---------------------

Finit handles SIGUSR1 and SIGUSR2 for reboot and halt, and listens to
``/dev/initctl`` so standard Linux reboot and halt commands should also
work.


Building
--------

The finit build system does not employ the GNU Configure and Build System,
instead standard makefiles are used. The user is encouraged to make source
code changes, using defines and conditionally building plugins instead to
alter the behavior of finit.

The following environment variables are checked by the makefiles and control
what is built and where resulting binaries are installed.

**ROOTDIR=**
   Top directory for building complete system, used in pretty printing

**VERSION=**
   Defaults to the currently released version of finit, e.g., 1.3 but can
   be overridden by packages to add a suffix or completely alter the version.

**CFLAGS=**
   Standard CFLAGS are inherited from the build environment.

**CPPFLAGS=**
   Standard CPPFLAGS are inherited from the build environment.

**LDFLAGS=**
   Standard LDFLAGS are inherited from the build environment.

**LDLIBS=**
   Standard LIBLIBS are inherited from the build environment.

**prefix=**
   Base prefix path for all files, except ``sbinbdir`` and ``sysconfdir``.
   Used in concert with the ``DESTDIR`` variable. Defaults to ``/usr``

**sbindir=**
   Path to where resulting binaries should install to. Used in concert
   with the ``DESTDIR`` variable. Defaults to ``/sbin``

**sysconfdir=**
   Path to where finit configuration files should install to. Used in
   concert with the ``DESTDIR`` variable.  Defaults to ``/etc``, but is
   currently unused.

**PLUGINS=**
   List of stock finit plugins to build and install.

**plugindir=**
   Absolute path to where finit should look for dynamically loadable plugins
   at runtime. At installation prepended by ``DESTDIR`` and ``prefix``.
   Defaults to ``/lib/finit/plugins``

**DESTDIR=**
   Used by packagers and distributions when building a relocatable
   bundle of files. Always prepended to the ``prefix`` destination
   directory.

**Example**::

  $ tar xfJ finit-1.3.tar.xz
  $ PLUGINS="initctl.so hwclock.so" DESTDIR=/tmp/finit/dst \
    make -C finit-1.3/ clean install
  make: Entering directory `/home/troglobit/finit-1.3'
    CC      finit.o
    CC      conf.o
    CC      helpers.o
    CC      sig.o
    CC      svc.o
    CC      plugin.o
    CC      strlcpy.o
    LINK    finit
    CC      plugins/initctl.o
    PLUGIN  plugins/initctl.so
    CC      plugins/hwclock.o
    PLUGIN  plugins/hwclock.so
    INSTALL /tmp/finit/dst/sbin/finit
    INSTALL /tmp/finit/dst/lib/finit/plugins/initctl.so
    INSTALL /tmp/finit/dst/lib/finit/plugins/hwclock.so
  make: Leaving directory `/home/troglobit/finit-1.3'

In this example the `finit-1.3.tar.xz`_ archive is unpacked to the
user's home directory, built and installed to a temporary staging
directory.  The environment variables ``DESTDIR`` and ``PLUGINS`` are
changed to suit this particular build.


Running
-------

The default install does not setup finit as the system default
``/sbin/init``, neither does it setup an initial ``/etc/finit.conf``.

It is assumed that users of finit are competent enough to either setup
finit as their default ``/sbin/init`` or alter their respective Grub,
LOADLIN, LILO, U-Boot/Barebox or RedBoot boot loader configuration to
give the kernel the following extra command line::

  init=/sbin/finit


Debugging
---------

Add ``finit_debug``, or ``--debug``, to the kernel command line to
enable trace messages.  A console getty is always started, see the file
``finit.h`` for more useful compile-time tweaks::

  init=/sbin/finit --debug


Contact
-------

This is the continuation of the `original finit`_ by Claudio Matsuoka,
which in turn was reverse engineered from syscalls of the `EeePC
fastinit`_ -- "gaps filled with frog DNA ...".  It is currently being
developed and maintained by `Joachim Nilsson`_ at `GitHub`_.  Please
file bug reports, clone it, or send pull requests for bug fixes and
proposed extensions.

.. _`SysV init`: https://en.wikipedia.org/wiki/Init
.. _`Joachim Nilsson`: http://troglobit.com
.. _GitHub: http://github.com/troglobit/finit
.. _`process supervision`: https://en.wikipedia.org/wiki/Process_supervision
.. _`daemontools`: http://cr.yp.to/daemontools.html
.. _`runit`: http://smarden.org/runit/
.. _`original finit`: http://helllabs.org/finit/
.. _`EeePC fastinit`: http://wiki.eeeuser.com/boot_process:the_boot_process
.. _upstart: http://upstart.ubuntu.com/
.. _runlevels: http://en.wikipedia.org/wiki/Runlevel
.. _systemd: http://www.freedesktop.org/wiki/Software/systemd/
.. _openrc: http://www.gentoo.org/proj/en/base/openrc/
.. _`finit-1.3.tar.xz`: ftp://troglobit.com/finit/finit-1.3.tar.xz
.. |cistatus| image:: https://travis-ci.org/troglobit/finit.png?branch=master
                      :target: https://travis-ci.org/troglobit/finit