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doc/config.md: Significant update, less limitations for /etc/finit.d
- Detail limitations in separate section - Focus on syntax early in document - Overhaul and simplify introduction Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
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Joachim Nilsson
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-54
@@ -4,39 +4,49 @@ Configuration
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Table of Contents
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-----------------
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* [/etc/finit.conf](#etcfinitconf)
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* [/etc/finit.d](#etcfinitd)
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* [Introduction](#introduction)
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* [Syntax](#syntax)
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* [Limitations](#limitations)
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* [/etc/finit.conf](#etcfinitconf)
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* [/etc/finit.d](#etcfinitd)
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Introduction
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------------
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Contrary to most other script based init alternatives (SysV [init][],
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[upstart][], [systemd][], [OpenRC][], etc.) Finit relies on its main
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configuration file `/etc/finit.conf` and `/etc/finit.d/`.
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Finit can be configured using only the original `/etc/finit.conf` file
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or in combination with `/etc/finit.d/*.conf`. Finit 3 can even start a
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system using only /etc/finit.d/*.conf`, highly useful for package-based
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Linux distributions -- each package can provide its own "script" file.
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The command line arguments given in `/etc/finit.conf` to each service
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provide a default. A plugin can be used to register a callback to a
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service and then modify the behavior to suit the current runlevel and
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system configuration.
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- `/etc/finit.conf`: main configuration file, read only once at boot
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- `/etc/finit.d/*.conf`: snippets, usually one service per file
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For instance, before starting a heavily resource intensive service like
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IPsec or OpenVPN, a callback can check if the outbound interface is up
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and has an IP address, or just check if the service is disabled — much
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like what a SysV init start script usually does.
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Not all configuration directives are available in `/etc/finit.d/*.conf`
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and some directives are only available at bootstrap, runlevel `S`, see
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the section [Limitations](#limitations) below for details.
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* `/etc/finit.conf`: main configuration file, read only once at boot
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* `/etc/finit.d/*.conf`: snippets, usually one service per file
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To add a new service, simply drop a `.conf` file in `/etc/finit.d` and
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run `initctl reload`. (It is also possible to `SIGHUP` to PID 1, or
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call `finit q`, but that has been deprecated with the `initctl` tool).
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Any service read from this directory is flagged as a dynamic service, so
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changes to or removal of `/etc/finit.d/*.conf` files, is detected.
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Only the `/etc/finit.d/*.conf` files are possible to reload at runtime,
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so usually only bootstrap (runlevel 'S') services are declared in the
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`/etc/finit.conf` file.
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On `initctl reload` the following is checked for all services:
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- If a service's `.conf` file has been removed, or its conditions are no
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longer satisifed, the service is stopped.
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- If the file is modified, or a service it depends on has been reloaded,
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the service is reloaded (stopped and started).
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- If a new service is added it is automatically started — respecting
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runlevels and return values from any callbacks.
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For more info on the different states of a service, see the separate
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document [Finit Services](service.md).
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/etc/finit.conf
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---------------
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Syntax:
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Syntax
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------
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* `module <MODULE>`
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Load a kernel module, with optional arguments
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@@ -229,46 +239,49 @@ Worth noting is that conditions is allowed for all these stanzas. For a
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detailed description, see the [Conditions](conditions.md) document.
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/etc/finit.d
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------------
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Limitations
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-----------
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Finit supports changes to the overall system configuration at runtime.
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For this purpose the (configurable) directory `/etc/finit.d` is used.
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Here you can put configuration file snippets, one per service if you
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like, which are all sourced automatically by finit at boot when loading
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the static configuration from `/etc/finit.conf`. This is the default
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behavior, so no include directives are necessary.
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To understand the limitations of `finit.conf` vs `finit.d` it is useful
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to picture the different phases of the system: bootstrap, runtime, and
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shutdown.
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To add a new service, simply drop a `.conf` file in `/etc/finit.d` and
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run `initctl reload`. (It is also possible to `SIGHUP` to PID 1, or
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call `finit q`, but that has been deprecated with the `initctl` tool).
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Any service read from this directory is flagged as a dynamic service, so
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changes to or removal of `/etc/finit.d/*.conf` files, is detected.
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### /etc/finit.conf
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On `initctl reload` the following is checked for all services:
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Started out as the only way to boot a system, later on runlevels for
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runtime was added. Hence, system hostname, network bringup and shutdown
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are natural parts to control in this file:
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- If a service's `.conf` file has been removed, or its conditions are no
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longer satisifed, the service is stopped.
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- If the file is modified, or a service it depends on has been reloaded,
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the service is reloaded (stopped and started).
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- If a new service is added it is automatically started — respecting
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runlevels and return values from any callbacks.
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- `host`
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- `mkdod`
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- `network`
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- `runparts`
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- `include`
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- `shtudown`
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- `runlevel`
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- ... and all configuration stanzas from `/etc/finit.d` below
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For more info on the different states of a service, see the separate
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document [Finit Services](service.md).
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### /etc/finit.d
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The `/etc/finit.d` directory was previously the default Finit `runparts`
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directory. Finit no longer has a default `runparts`, so make sure to
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update your setup, or the finit configuration, accordingly.
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Support for partial `.conf` files in `/etc/finit.d` was added to handle
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changes of the system configuration at runtime. It does *not support*
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the above `finit.conf` settings described above.
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**Note:** Configurations read from `/etc/finit.d` are read *after*
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initial bootstrap, runlevel S(1). Hence, bootstrap services *must* be
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in `/etc/finit.conf`!
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Supported stanzas are:
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- `module`, but only in runlevel `S`
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- `service`
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- `task`
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- `run`
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- `inetd`
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- `rlimit`
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- `tty`
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- `console`
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**NOTE:*** The `/etc/finit.d` directory was previously the default Finit
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`runparts` directory. Finit no longer has a default `runparts`, make
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sure to update your setup, or the finit configuration, accordingly.
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[init]: http://en.wikipedia.org/wiki/Init
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[upstart]: http://upstart.ubuntu.com/
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[systemd]: http://www.freedesktop.org/wiki/Software/systemd/
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[openrc]: http://www.gentoo.org/proj/en/base/openrc/
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[run-parts(8)]: http://manpages.debian.org/cgi-bin/man.cgi?query=run-parts
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