Finit: Fast Init

Table of Contents ----------------- [![Travis Status]][Travis] [![Coverity Status]][Coverity Scan] * [Introduction](#introduction) * [Features](#features) * [/etc/finit.conf](doc/config.md#etcfinitconf) * [/etc/finit.d](doc/config.md#etcfinitd) * [Runparts & /etc/rc.local](#runparts--etcrclocal) * [Bootstrap](doc/bootstrap.md#bootstrap) * [Runlevels](#runlevels) * [Inetd](doc/inetd.md#inetd) * [Hooks, Callbacks & Plugins](doc/plugins.md#hooks-callbacks--plugins) * [Rebooting & Halting](#rebooting--halting) * [Commands & Status](#commands--status) * [Building](doc/build.md#building) * [Requirements](#requirements) * [Running](#running) * [Debugging](#debugging) * [Origin & References](#origin--references) Introduction ------------ Finit is an EeePC Fastinit inspired clone with [process supervision][1] similar to that of D.J. Bernstein's [daemontools][2] and Gerrit Pape's [runit][3]. It also supports free-form conditions based on events, e.g. triggering on PID file creation, Netlink events like a default route or interfaces coming up, or even custom events. Similar to [systemd][6]. Finit focuses on small and embedded Linux systems, although fully usable on servers and desktops as well. See the [contrib section](contrib/) for Debian and Alpine Linux examples. Traditional [SysV init][4] style systems are scripted. For low-resource embedded systems this is quite resource intensive and often leads to long boot times. Finit reduces context switches and forking of shell scripts to provide a swift [system bootstrap](doc/bootstrap.md) written entirely in C. Configuration is read from [/etc/finit.conf](doc/config.md#etcfinitconf) which details kernel modules to load, services and TTYs to start. When initial [bootstrap](doc/bootstrap.md) is done, including setting up networking, [/etc/finit.d/](doc/config.md#etcfinitd) and the familiar [/etc/rc.local](#runparts--etcrclocal) are run. **Example /etc/finit.conf:** ``` # Fallback if /etc/hostname is missing host wopr # Runlevel to start after bootstrap, runlevel 'S' runlevel 2 # Services to be monitored and respawned as needed service [S12345] /sbin/watchdogd -L -f -- System watchdog daemon service [S12345] /sbin/syslogd -n -b 3 -D -- System log daemon service [S12345] /sbin/klogd -n -- Kernel log daemon service [2345] /sbin/lldpd -d -c -M1 -H0 -i -- LLDP daemon (IEEE 802.1ab) # For multiple instances of the same service, add :ID somewhere between # the service/run/task keyword and the command. service :1 [2345] /sbin/merecat -n -p 80 /var/www -- Web server service :2 [2345] /sbin/merecat -n -p 8080 /var/www -- Old web server # Alternative method instead of below runparts, can also use /etc/rc.local #task [S] /etc/init.d/keyboard-setup start -- Setting up preliminary keymap #task [S] /etc/init.d/acpid start -- Starting ACPI Daemon #task [S] /etc/init.d/kbd start -- Preparing console # Inetd services to start on demand, with alternate ports and filtering inetd ftp/tcp nowait [2345] /sbin/uftpd -i -f -- FTP daemon inetd tftp/udp wait [2345] /sbin/uftpd -i -y -- TFTP daemon inetd time/udp wait [2345] internal -- UNIX rdate service inetd time/tcp nowait [2345] internal -- UNIX rdate service inetd 3737/tcp nowait [2345] internal.time -- UNIX rdate service inetd telnet/tcp nowait [2345] /sbin/telnetd -i -F -- Telnet daemon inetd 2323/tcp nowait [2345] /sbin/telnetd -i -F -- Telnet daemon inetd 222/tcp@eth0 nowait [2345] /sbin/dropbear -i -R -F -- SSH service inetd ssh/tcp@*,!eth0 nowait [2345] /sbin/dropbear -i -R -F -- SSH service # Run start scripts from this directory # runparts /etc/start.d # Virtual consoles to start built-in getty on tty [12345] /dev/tty1 115200 linux tty [12345] /dev/ttyAMA0 115200 vt100 ``` For an example of a full blown embedded Linux, see [TroglOS][9], or take a look at the `contrib/` section with [Alpine Linux](contrib/alpine/), [Debian](contrib/debian/), support and more. Features -------- **Process Supervision** Start, monitor and restart services should they fail. **Inetd** Finit comes with a built-in [inetd server](doc/inetd.md). No need to maintain a separate config file for services that you want to start on demand. All inetd services started can be filtered per port and inbound interface, reducing the need for a full blown firewall. Built-in optional inetd services: - echo RFC862 - chargen RFC864 - daytime RFC867 - discard RFC863 - time (rdate) RFC868 For more information, see [doc/inetd.md](doc/inetd.md). **Getty** Finit also comes with a built-in Getty for Linux console TTYs. It can parse `/etc/inittab` and set the speed. Then `/bin/login` handles all nasty bits with PAM etc. # /etc/finit.conf tty [12345] /dev/tty1 38400 linux tty [12345] /dev/ttyAMA0 115200 vt100 **Runlevels** Support for SysV init-style [runlevels][5] is available, in the same minimal style as everything else in Finit. The `[2345]` syntax can be applied to service, task, run, inetd, and TTY stanzas. 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. init 4, but also using the more advanced `intictl` tool. **Plugins** Plugins can *extend* the functionality of Finit and *hook into* the different stages of the boot process and at runtime. Plugins are written in C and compiled into a dynamic library loaded automatically by finit at boot. A basic set of plugins are bundled in the `plugins/` directory. Capabilities: - **Hooks** Hook into the boot at predefined points to extend Finit - **I/O** Listen to external events and control Finit behavior/services - **Inetd** Extend Finit with internal inetd services, for an example, see `plugins/time.c` 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. For more information, see [doc/plugins.md](doc/plugins.md). Runparts & /etc/rc.local ------------------------ At the end of the boot, when networking and all services are up, Finit calls its built-in [run-parts(8)][] on the `runparts ` directory, and `/etc/rc.local`, in that order if they exist. ```shell runparts /etc/rc.d/ ``` No configuration stanza in `/etc/finit.conf` is required for `rc.local`. If it exists and is an executable shell script, finit calls it at the very end of the boot, before calling the `HOOK_SYSTEM_UP`. See more on hooks in [doc/plugins.md](doc/plugins.md#hooks), and about the system bootstrap in [doc/bootstrap.md](doc/bootstrap.md). Runlevels --------- Basic support for [runlevels][5] 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. Finit supports runlevels 0-9, and S, with 0 reserved for halt, 6 reboot and S for services to only run at bootstrap. Runlevel 1 is the single user level, where usually no networking is enabled. In Finit this is more of a policy for the user to define. Normally only runlevels 1-6 are used, and even more commonly, only the default runlevel is used. To specify an allowed set of runlevels for a `service`, `run` command, `task`, or `tty`, add `[NNN]` to 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 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 syslogd is first started, in parallel, and then acpid is called using a conventional SysV init script. It is called with the run command, meaning the following task command to start the kbd script is not called until the acpid init script has fully completed. Then the keyboard setup script is called in parallel with klogd as a monitored service. Again, tasks and services are started in parallel, while run commands 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. When changing runlevels Finit also automatically reloads all `.conf` files in the `/etc/finit.d/` directory. So if you want to set a new system config, switch to runlevel 1, change all config files in the system, and touch all `.conf` files in `/etc/finit.d` before switching back to the previous runlevel again — that way Finit can both stop old services and start any new ones for you, without rebooting the system. Rebooting & Halting ------------------- Traditionally, rebooting and halting a UNIX system is done by changing its runlevel. Finit comes with its own tooling providing: `shutdown`, `reboot`, `poweroff`, and `suspend`, but also the traditional `init` and `telinit`, as well as a more modern `initctl` tool, detailed in the next section. For compatibility reasons Finit listens to the same set of signals as BusyBox init. This is not 100% compatible with SysV init, but clearly the more common combination for Finit. For more details, see [doc/signals.md](doc/signals.md). Finit also listens to the classic SysV init FIFO, used by `telinit`. Support for this is implemented by the `initctl.so` plugin. Hence, `telinit q` will work as the UNIX beards intended. ~ # telinit -h Usage: telinit [OPTIONS] [q | Q | 0-9] Options: -h, --help This help text -V, --version Show Finit version Commands: 0 Power-off the system, same as initctl poweroff 6 Reboot the system, same as initctl reboot 2, 3, 4, 5 Change runlevel. Starts services in new runlevel, stops any services in prev. runlevel that are not allowed in new. q, Q Reload *.conf in /etc/finit.d/, same as initctl reload or sending SIGHUP to PID 1 1, s, S Enter system rescue mode, runlevel 1 Commands & Status ----------------- Finit also implements a more modern API to query status, and start/stop services, called `initctl`. Unlike `telinit` the `initctl` tool does not return until the given command has fully completed. ~ $ initctl -h Usage: initctl [OPTIONS] Options: -d, --debug Debug initctl (client) -v, --verbose Verbose output -h, --help This help text Commands: debug Toggle Finit (daemon) debug help This help text reload Reload *.conf in /etc/finit.d/ and activate changes runlevel [0-9] Show or set runlevel: 0 halt, 6 reboot status | show Show status of services cond set Set (assert) condition => +COND cond clear Clear (deassert) condition => -COND cond flux Emulate flux condition => ~COND cond show Show condition status start [:ID] Start service by job# or name, with optional ID stop [:ID] Stop/Pause a running service by job# or name restart [:ID] Restart (stop/start) service by job# or name reload [:ID] Reload (SIGHUP) service by job# or name version Show Finit version For services *not* supporting `SIGHUP` the `` notation in the .conf file must be used to tell Finit to stop and start it on `reload` and `runlevel` changes. If `<>` holds more [conditions](doc/conditions.md), these will also affect how a service is maintained. **Note:** even though it is possible to start services not belonging in the current runlevel these services will not be respawned automatically by Finit if they exit (crash). Hence, if the runlevel is 2, the below Dropbear SSH service will not be restarted if it is killed or exits. ~ $ initctl status -v 1 running 476 [S12345] /sbin/watchdog -T 16 -t 2 -F /dev/watchdog 2 running 477 [S12345] /sbin/syslogd -n -b 3 -D 3 running 478 [S12345] /sbin/klogd -n 4:1 inetd 0 [2345] internal time allow *:37 4:2 inetd 0 [2345] internal time allow *:37 4:3 inetd 0 [2345] internal 3737 allow *:3737 5:1 inetd 0 [2345] /sbin/telnetd allow *:23 deny eth0,eth1 5:2 inetd 0 [2345] /sbin/telnetd allow eth0:2323,eth2:2323,eth1:2323 6:1 inetd 0 [345] /sbin/dropbear allow eth0:222 6:2 inetd 0 [345] /sbin/dropbear allow *:22 deny eth0 Requirements ------------ Finit is capable of running on both desktop/server systems with udev and embedded systems that usually come with BusyBox mdev. Finit probes for them at runtime and expects `/dev/` to be writable, usually `devtmpfs`. It is also possible to run on a statically set up `/dev` if needed. It is however not a good idea to have both udev and mdev installed at the same time, this will lead to unpredictable results. At boot Finit calls either `mdev` or `udevd` to populate `/dev`, this is done slightly differently and on systems with udev you might want to add the following one-shot task early in your `/etc/finit.conf`: run [S] /sbin/udevadm settle --timeout=120 -- Waiting for udev Finit has a built-in Getty for TTYs, but requires a working `/bin/login` or `/bin/sh`, if no TTYs are configured in `/etc/finit.conf`. For a fully operational system `/var`, `/run` and `/tmp` must be set up properly in `/etc/fstab` -- which is iterated over at boot. The built-in Inetd requires `/etc/services` and `/etc/protocols` to work with port names rather than numbers. Running ------- Having successfully [built Finit](doc/build.md) it may now be time to take it for a test drive. The `make install` attempts to set up finit as the system system init, `/sbin/init`, but this is usually a symlink pointing to the current init. So either change the symlink, or change your boot loader (GRUB, LOADLIN, LILO, U-Boot/Barebox or RedBoot) configuration to append the following to the kernel command line: ```shell append="init=/sbin/finit" ``` Remember to also set up an initial `/etc/finit.conf` before rebooting! ![Finit starting TroglOS](images/finit3-screenshot.png "Finit screenshot") Debugging --------- Add `finit_debug`, or `--debug`, to the kernel command line to enable debug messages. ```shell append="init=/sbin/finit --debug" ``` To debug startup issues, in particular issues with getty/login, try `configure --enable-fallback-shell`. When no TTYs are detected, and Finit is configured with this option, Finit will try to start a bare `/bin/sh` on the boot console. Origin & References ------------------- This project is based on the [original finit][] by [Claudio Matsuoka][] which was reverse engineered from syscalls of the [EeePC fastinit][] — "gaps filled with frog DNA …" Finit is developed and maintained by [Joachim Nilsson][] at [GitHub][]. 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]: https://www.freedesktop.org/wiki/Software/systemd/ [9]: https://github.com/troglobit/troglos [run-parts(8)]: http://manpages.debian.org/cgi-bin/man.cgi?query=run-parts [original finit]: http://helllabs.org/finit/ [EeePC fastinit]: http://wiki.eeeuser.com/boot_process:the_boot_process [Claudio Matsuoka]: https://github.com/cmatsuoka [Joachim Nilsson]: http://troglobit.com [GitHub]: https://github.com/troglobit/finit [Travis]: https://travis-ci.org/troglobit/finit [Travis Status]: https://travis-ci.org/troglobit/finit.png?branch=master [Coverity Scan]: https://scan.coverity.com/projects/3545 [Coverity Status]: https://scan.coverity.com/projects/3545/badge.svg