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