Warsaw, 1998.07.07 This README shortly describes the features of "oinit" - a very simplistic version of init(8) combined with a shell. Features -------- * oinit is able to run system in multi- and single-user modes, * it can be started on system with DEVFS/SLICE (i.e. empty /dev), * provides minimalistic user interface, called "shell()", * it can run the system startup script (/etc/rc), * it can be compiled with -DOINIT_RC to use its own startup script (*very* primitive, but doesn't require any real shell to run it!), * doesn't require the whole chain of init->getty->login->shell to be run, * it is extremely small, and is ideally suited for situations when there is little memory. As an additional bonus you receive some obvious and some hidden bugs... :-)) This code is at most alpha quality yet. How it works ------------ Unlike normal init(8), it forks itself on given number of vty's immediately providing shell() interface. Currently it doesn't require (and is unable to perform) any authentication, but this is easy to add if needed. Standard version of FreeBSD kernel looks for /sbin/init first, and then tries to execute it. If it fails, it tries to find: /sbin/oinit /sbin/init.bak /stand/sysinstall So it is easy to make use of it even on standard system - just put it in /sbin/oinit and rename /sbin/init to something else, e.g. /sbin/init.bak. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Init (or oinit) plays crucial role in the system. If you plan to do any changes to your system's init, make sure you have a boot floppy with working version of statically compiled init(8) on it - you can very easily put your system in unusable state when fiddling with it. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Shell() interface ----------------- It allows you to issue built-in and external commands. Built-in commands are listed below. For each command there is short help available, with example of usage. cd change working directory pwd print working directory set set environment variable (no expansion) unset unset environment variable env print all environment variables echo echo arguments on stdout exit exit from shell (oinit will start a new one after some delay) . source-in a file with commands ? help Any other command is passed to execvp(3) as it is. EXCEPTION: if you end the command line with a '&', the command is started as daemon. This is NOT the same as in normal shell, where the '&' puts a process in background. Here the newly started process is totally dissociated from terminal. Prompt tells you: * your `pwd` * your PID * and that you are root ('#'). WARNING: this pseudo-shell doesn't do any expansion whatsoever. To do list ---------- - oinit proper: * fix signal handling and transitions, * invent a one-file configuration database (combining as many files from /etc as possible into one) able to properly handle inter- dependencies in running various daemons, * allow for interpreting of such database, and running various programs ourselves (this would eventually allow to make /bin/sh an option, not necessity), * better hooks for incorporating other modules into oinit (see e.g. the telnet() below), * add optional authentication, - shell(): * more built-ins: perhaps 'kill' and 'ps', * variable expansion, * globbing, * conditionals, * history? (it depends on how much memory it needs). * programmatic hooks for easy customisation of user interface (like hierarchy of commands and contexts), * ... - implement as a routine (like shell()) a small remote login daemon telnet(), as a built-in module to oinit. It would implement the simplest options of normal telnet, and would itself handle authentication, passing control to shell() on success. The authentication routine would be the same as for checking console access. And allow me for a moment of day-dreaming: I'd like to rewrite oinit one day to be a monolithic one-in-all application, non-forking but multithreaded... It would contain all the modules, such as shell(), telnet(), ifconfig() etc... started as threads, not separate processes. Credits ------- The overall framework was taken from FreeBSD /sbin/init. Andrzej Bialecki $Id: README,v 1.1.1.1 1998/08/27 17:38:45 abial Exp $