README
1Warsaw, 1998.07.07
2
3This README shortly describes the features of "oinit" - a very simplistic
4version of init(8) combined with a shell.
5
6Features
7--------
8
9* oinit is able to run system in multi- and single-user modes,
10* it can be started on system with DEVFS/SLICE (i.e. empty /dev),
11* provides minimalistic user interface, called "shell()",
12* it can run the system startup script (/etc/rc),
13* it can be compiled with -DOINIT_RC to use its own startup script
14 (*very* primitive, but doesn't require any real shell to run it!),
15* doesn't require the whole chain of init->getty->login->shell to be run,
16* it is extremely small, and is ideally suited for situations when
17 there is little memory.
18
19As an additional bonus you receive some obvious and some hidden bugs... :-))
20This code is at most alpha quality yet.
21
22
23How it works
24------------
25
26Unlike normal init(8), it forks itself on given number of vty's immediately
27providing shell() interface. Currently it doesn't require (and is unable to
28perform) any authentication, but this is easy to add if needed.
29
30Standard version of FreeBSD kernel looks for /sbin/init first, and then
31tries to execute it. If it fails, it tries to find:
32 /sbin/oinit
33 /sbin/init.bak
34 /stand/sysinstall
35
36So it is easy to make use of it even on standard system - just put it in
37/sbin/oinit and rename /sbin/init to something else, e.g. /sbin/init.bak.
38
39+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
40!!! WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!!
41+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
42Init (or oinit) plays crucial role in the system. If you plan to do any
43changes to your system's init, make sure you have a boot floppy with working
44version of statically compiled init(8) on it - you can very easily put your
45system in unusable state when fiddling with it.
46+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
47
48Shell() interface
49-----------------
50
51It allows you to issue built-in and external commands. Built-in commands
52are listed below. For each command there is short help available, with
53example of usage.
54
55 cd change working directory
56 pwd print working directory
57 set set environment variable (no expansion)
58 unset unset environment variable
59 env print all environment variables
60 echo echo arguments on stdout
61 exit exit from shell (oinit will start a new one after some delay)
62 . source-in a file with commands
63 ? help
64
65Any other command is passed to execvp(3) as it is.
66
67EXCEPTION: if you end the command line with a '&', the command is started
68as daemon. This is NOT the same as in normal shell, where the '&' puts a
69process in background. Here the newly started process is totally dissociated
70from terminal.
71
72Prompt tells you:
73* your `pwd`
74* your PID
75* and that you are root ('#').
76
77WARNING: this pseudo-shell doesn't do any expansion whatsoever.
78
79To do list
80----------
81
82- oinit proper:
83 * fix signal handling and transitions,
84 * invent a one-file configuration database (combining as many files
85 from /etc as possible into one) able to properly handle inter-
86 dependencies in running various daemons,
87 * allow for interpreting of such database, and running various
88 programs ourselves (this would eventually allow to make /bin/sh
89 an option, not necessity),
90 * better hooks for incorporating other modules into oinit (see e.g.
91 the telnet() below),
92 * add optional authentication,
93
94- shell():
95 * more built-ins: perhaps 'kill' and 'ps',
96 * variable expansion,
97 * globbing,
98 * conditionals,
99 * history? (it depends on how much memory it needs).
100 * programmatic hooks for easy customisation of user interface (like
101 hierarchy of commands and contexts),
102 * ...
103
104- implement as a routine (like shell()) a small remote login daemon telnet(),
105 as a built-in module to oinit. It would implement the simplest options of
106 normal telnet, and would itself handle authentication, passing control to
107 shell() on success. The authentication routine would be the same as for
108 checking console access.
109
110And allow me for a moment of day-dreaming: I'd like to rewrite oinit one day
111to be a monolithic one-in-all application, non-forking but multithreaded... It
112would contain all the modules, such as shell(), telnet(), ifconfig() etc...
113started as threads, not separate processes.
114
115Credits
116-------
117
118The overall framework was taken from FreeBSD /sbin/init.
119
120Andrzej Bialecki
121<abial@freebsd.org>
122
123$FreeBSD$
124