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Cleanup README for release.

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Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
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Joachim Nilsson
2015-01-24 16:04:54 +01:00
parent 9e446557b4
commit dcb42602c9
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README.md
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@@ -27,36 +27,31 @@ Introduction
Init is the first process to run once a UNIX kernel has booted, it
always has PID 1 and is responsible for starting up the rest of the
system. Finit is a very small plugin based init with built in
[process supervision](https://en.wikipedia.org/wiki/Process_supervision)
similar to that of D.J. Bernstein's
[daemontools](http://cr.yp.to/daemontools.html) and Gerrit Pape's
[runit](http://smarden.org/runit/). The focus of Finit is on small and
embedded GNU/Linux systems, although it is fully functional for standard
server and desktop installations as well.
system. Finit is plugin-based with built in [process supervision][1]
similar to that of D.J. Bernstein's [daemontools][2] and Gerrit Pape's
[runit][3]. The main focus of Finit is on small and embedded GNU/Linux
systems, yet fully functional on standard server and desktop
installations as well.
Finit has a low overhead because it is written entirely in C. System
setup, otherwise commonly done with scripts, is instead done using a
slimmed down set of system calls directly to the C-library. As soon as
basic setup is done, Finit launches services in parllel and monitor them
continouosuly, i.e. automatically restart them if they fail.
Traditional [SysV init][4] style systems are scripted. For low-resource
embedded systems this can be quite resource intensive and cause longer
boot times. Finit is optimized to reduce context switches and forking
of processes to provide a very basic bootstrap written entirely in C.
Hence, there is no `/etc/init.d/rcS` script, or similar, but instead a
human-readable `/etc/finit.conf`. This file details what kernel modules
to load, programs to run and daemons to supervise.
Alls services can have callbacks that are called before a service is
(re)started. For instance, before attempting to start a heavily
resource intensive service like IPsec or OpenVPN, a callback can check
if the outbound interface is up and has an IP address, or just check if
the service is disabled -- much like what a SysV init start script
usually does.
The command line arguments given in `/etc/finit.conf` to each service
provide a default. Each service can register callbacks, using plugins,
to override and modify the behavior to suit the current runlevel and
system configuration. For instance, before starting a heavily resource
intensive service like IPsec or OpenVPN, a callback can check if the
outbound interface is up and has an IP address, or just check if the
service is disabled -- much like what a SysV init start script usually
does.
To extend finit with new functionality, hooks in the bootstrap phase can
be added that execute in sequence, useful for satisfying preconditions
or for synchronization purposes. Functionality can also be added with
plugins, the initctl compatibility plugin that comes with finit is one
such plugin.
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 and examples.
See [TroglOS][9] for an example of how to boot a small embedded system
with Finit.
Features
@@ -68,12 +63,19 @@ Start, monitor and restart services if they fail.
**Runlevels**
Finit supports standard runlevels if you want, but you don't need them
for simple installations.
Runlevels is optional in Finit, but support for [SysV runlevels][5] is
available if needed. All services in runlevel S(1) are started first,
followed by the desired run-time runlevel. Runlevel S can be started in
sequence by using `run [S] cmd`. Changing runlevels at runtime is done
like any other init, e.g. <kbd>init 4</kbd>.
**Plugins**
Extend and modify finit behavior. See examples in plugins/ directory.
Finit plugins can be either *boot hooks* into different stages of the
boot process or *service callbacks*, or both. A basic set of plugins
that extend and modify the basic behavior are bundled. See examples in
the `plugins/` directory.
Plugin capabilities:
* Service callbacks -- modify service arguments, run/restart/stop
@@ -81,7 +83,7 @@ Plugin capabilities:
* 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
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.
@@ -89,12 +91,11 @@ hook into the boot process or respond to various I/O.
/etc/finit.conf
---------------
Contrary to most other script based init alternatives
([SysV init](https://en.wikipedia.org/wiki/Init),
[upstart](http://upstart.ubuntu.com/),
[systemd](http://www.freedesktop.org/wiki/Software/systemd/),
[OpenRC](http://www.gentoo.org/proj/en/base/openrc/) and the likes)
finit reads its configuration from `/etc/finit.conf`. Syntax:
Contrary to most other script based init alternatives ([SysV init][4],
[upstart][6], [systemd][7], [OpenRC][8], etc.) Finit reads its entire
configuration from `/etc/finit.conf`.
Syntax:
* `check <DEV>`
@@ -158,8 +159,8 @@ finit reads its configuration from `/etc/finit.conf`. Syntax:
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
When running <kbd>make install</kbd> no default `/etc/finit.conf` will
be installed since 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!
@@ -226,7 +227,7 @@ 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 your `finit.conf`, like this:
or `tty`, add `[NNN]` to it in your `/etc/finit.conf`, like this:
service [S12345] /sbin/syslogd -n -x -- System log daemon
run [S] /etc/init.d/acpid start -- Starting ACPI Daemon
@@ -251,7 +252,7 @@ are called in the order listed and subsequent commands are not started
until a run command has completed.
Switching between runlevels can be done by calling init with a single
argument, e.g., `init 5` switches to runlevel 5.
argument, e.g. <kbd>init 5</kbd> switches to runlevel 5.
Hooks, Callbacks & Plugins
@@ -385,9 +386,15 @@ what is built and where resulting binaries are installed.
**Example**
$ tar xfJ finit-1.3.tar.xz
$ PLUGINS="initctl.so hwclock.so" DESTDIR=/tmp/finit/dst \
make -C finit-1.3/ clean install
First, unpack the archive:
<kbd>$ tar xfJ finit-1.3.tar.xz</kbd>
Then build and install:
<kbd>$ PLUGINS="initctl.so hwclock.so" DESTDIR=/tmp/finit/dst \
make -C finit-1.3/ clean install</kbd>
make: Entering directory `/home/troglobit/finit-1.3'
CC finit.o
CC conf.o
@@ -406,12 +413,10 @@ what is built and where resulting binaries are installed.
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](ftp://troglobit.com/finit/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.
In this example the [finit-1.3.tar.xz][10] 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
@@ -454,3 +459,13 @@ Finit is currently being developed and maintained by
[GitHub](http://github.com/troglobit/finit). Please file bug reports, clone it,
or send pull requests for bug fixes and proposed extensions.
[1]: https://en.wikipedia.org/wiki/Process_supervision
[2]: http://cr.yp.to/daemontools.html
[3]: http://smarden.org/runit/
[4]: http://en.wikipedia.org/wiki/Init
[5]: http://en.wikipedia.org/wiki/Runlevel
[6]: http://upstart.ubuntu.com/
[7]: http://www.freedesktop.org/wiki/Software/systemd/
[8]: http://www.gentoo.org/proj/en/base/openrc/
[9]: https://github.com/troglobit/troglos
[10]: ftp://troglobit.com/finit/finit-1.3.tar.xz