Annotation of sys/arch/i386/stand/boot/boot.8, Revision 1.1.1.1
1.1 nbrk 1: .\" $OpenBSD: boot.8,v 1.47 2007/05/31 19:20:03 jmc Exp $
2: .\"
3: .\" Copyright (c) 1997-2001 Michael Shalayeff
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28: .Dd $Mdocdate: May 31 2007 $
29: .Dt BOOT 8 i386
30: .Os
31: .Sh NAME
32: .Nm boot ,
33: .Nm boot.conf
34: .Nd
35: i386-specific second-stage bootstrap
36: .Sh DESCRIPTION
37: The main purpose of this program is to load the system kernel while dealing
38: with the downfalls of the PC BIOS architecture.
39: .Pp
40: As described in
41: .Xr boot_i386 8 ,
42: this program is loaded by the
43: .Xr biosboot 8
44: primary bootstrap loader and provides a convenient way to load the kernel.
45: This program acts as an enhanced boot monitor for PC systems, providing
46: a common interface for the kernel to start from.
47: .Pp
48: Basic operations include:
49: .Pp
50: .Bl -bullet -compact
51: .It
52: Detecting and switching between multiple consoles.
53: .It
54: Loading kernels from any device supported by your system BIOS.
55: .It
56: Loading kernels compressed by
57: .Xr gzip 1 .
58: .It
59: Passing system parameters queried from the BIOS to the kernel.
60: .It
61: Providing an interactive command line.
62: .El
63: .Pp
64: The sequence of its operation is as follows: initialization,
65: parsing the configuration file, then an interactive command line.
66: While at the command line you have 5 seconds to type any commands, if needed.
67: If time expires, the kernel will be loaded according to
68: the current variable settings (see the
69: .Nm set
70: command).
71: Each time a kernel load fails, the timeout is increased by one second.
72: The sequence of
73: .Nm
74: operations is as follows:
75: .Bl -enum
76: .It
77: Set up a protected mode environment which catches and reports processor
78: exceptions and provides a simple protected-mode BIOS interface.
79: .It
80: Probe for console devices, which includes the (default) PC VGA+Keyboard
81: console
82: .Pq Li pc0
83: and up to four serial consoles
84: .Pf ( Li com0
85: through
86: .Li com3 )
87: connected to the serial ports.
88: Display messages to the default console about the devices found.
89: .It
90: Detect memory.
91: Conventional memory is detected by querying the BIOS.
92: Extended memory is detected by probing page-by-page through the address
93: space, rather than asking the BIOS; many BIOS's cannot report larger than
94: 64M of memory.
95: All memory found is reported to the default console device.
96: .It
97: Probe for APM support in the BIOS.
98: Display a message if support is present.
99: .It
100: If the file
101: .Pa /etc/boot.conf
102: exists on the filesystem
103: .Nm
104: was loaded from, open and parse it.
105: This file may contain any commands
106: .Nm
107: accepts at the interactive prompt.
108: Though default settings usually suffice, they can be changed here.
109: .Pp
110: .Pa boot.conf
111: processing can be skipped by holding down either Control key as
112: .Nm
113: starts.
114: .It
115: The header line
116: .Pp
117: .Dl >> OpenBSD/i386 BOOT [x.xx]
118: .Pp
119: is displayed to the active console, where
120: .Ar x.xx
121: is the version number of the
122: .Nm
123: program, followed by the
124: .Pp
125: .Dl boot>
126: .Pp
127: prompt, which means you are in interactive mode and may enter commands.
128: If you do not,
129: .Nm
130: will proceed to load the kernel with the current parameters after the
131: timeout period has expired.
132: .El
133: .Pp
134: By default,
135: .Nm
136: attempts to load the kernel executable
137: .Pa /bsd .
138: If it fails to find the kernel and no alternative kernel image has
139: been specified, the system will be unable to boot.
140: .Sh COMMANDS
141: The following commands are accepted at the
142: .Nm
143: prompt:
144: .Bl -tag -width shorten
145: .It boot Op Ar image Op Fl acds
146: Boots the kernel image specified by
147: .Ar image
148: with any options given.
149: Image specification consists of a pair
150: .Ar device : Ns Ar filename ;
151: either or both can be omitted (`:' is not needed if both are omitted),
152: in which case values from
153: .Nm
154: variables will be used.
155: .Pp
156: When selecting the
157: .Ar device
158: to boot from,
159: .Nm
160: makes no distinction between SCSI and IDE type drives;
161: they are detected as
162: .Sq hd
163: devices.
164: Therefore, to boot kernel
165: .Pa /bsd
166: from slice
167: .Sq a
168: on the first hard drive
169: .Pq irrespective of device type ,
170: specify
171: .Dq boot hd0a:/bsd .
172: .Bl -tag -width _a_
173: .It Fl a
174: Causes the kernel to ask for the
175: .Nm root
176: device to use.
177: .It Fl c
178: Causes the kernel to go into
179: .Xr boot_config 8
180: before performing
181: .Xr autoconf 4
182: procedures.
183: .It Fl d
184: Causes the kernel to drop into
185: .Xr ddb 4
186: at the earliest convenient point.
187: .It Fl s
188: Causes the kernel to boot single-user.
189: .El
190: .It echo Op Ar args
191: Displays
192: .Ar args
193: on the console device.
194: .It help
195: Prints a list of available commands and machine dependent
196: commands, if any.
197: .It machine Op Ar command
198: Issues machine-dependent commands.
199: These are defined for i386 architecture:
200: .Bl -tag -width diskinfo
201: .It Nm diskinfo
202: Prints a list of hard disks installed on your system including:
203: BIOS device number, and the BIOS geometry.
204: .It Nm memory
205: If used without any arguments, this command will print out
206: the memory configuration as determined through BIOS routines.
207: Otherwise the arguments specify how to modify the
208: memory configuration.
209: They take the form of:
210: .Pp
211: .Dl [+-]<size>@<address>
212: .Pp
213: Meaning to add(+) or exempt(-) the amount of memory specified by
214: .Ar <size>
215: at the location specified by
216: .Ar <address> .
217: Both size and base address can be specified as octal,
218: decimal, or hexadecimal numbers, as accepted by the
219: .Xr strtoul 3
220: routine.
221: .Pp
222: Memory segments are not required to be adjacent to each other;
223: the only requirement is that there is real physical memory under
224: the range added.
225: The following example
226: adds 32M of memory right after the first 16M:
227: .Bd -unfilled -offset indent
228: machine mem +0x2000000@0x1000000
229: .Ed
230: .Pp
231: Another useful command is to withdraw a range
232: of memory from OS usage (it may have been wrongfully reported as
233: useful by the BIOS).
234: This example
235: effectively excludes the 15\(en16M range from the map of useful memory:
236: .Bd -unfilled -offset indent
237: machine mem -0x100000@0xf00000
238: .Ed
239: .It Nm regs
240: Prints contents of processor registers if compiled with
241: .Em DEBUG .
242: .El
243: .It ls Op Ar directory
244: Prints contents of the specified
245: .Ar directory
246: in long format including: attributes and file type, owner, group,
247: size, filename.
248: .It reboot
249: Reboots the machine by initiating a warm boot procedure.
250: .It set Op Ar varname Op Ar value
251: If invoked without arguments, prints a list of variables and their values.
252: If only
253: .Ar varname
254: is specified, displays contents of that variable.
255: If
256: .Ar varname
257: and
258: .Ar value
259: are both specified, sets that variable to the given value.
260: Variables include:
261: .Pp
262: .Bl -tag -compact -width boothow
263: .It Nm addr
264: Address at which to load the kernel.
265: .It Nm debug
266: Debug flag if
267: .Nm
268: was compiled with DEBUG defined.
269: .It Nm device
270: Boot device name (e.g.,
271: .Li fd0a ,
272: .Li hd0a ) .
273: .It Nm howto
274: Options to pass to the loaded kernel.
275: .It Nm image
276: File name containing the kernel image.
277: .It Nm timeout
278: Number of seconds boot will wait for human intervention before
279: booting the default kernel image.
280: .It Nm tty
281: Active console device name (e.g.,
282: .Li com0 ,
283: .Li com1 ,
284: .Li pc0 ) .
285: .El
286: .It stty Op Ar device Op Ar speed
287: Displays or sets the
288: .Ar speed
289: for a console
290: .Ar device .
291: If changing the baudrate for the currently active console,
292: .Nm
293: offers you five seconds of grace time before committing the change
294: to allow you to change your terminal's speed to match.
295: If changing speed
296: .Em not
297: for the active console, the baudrate is set for the
298: .Em next
299: time you switch to a serial console.
300: The baudrate value is not used for the
301: .Li pc0
302: console.
303: .Pp
304: The default baudrate is 9600bps.
305: .It time
306: Displays system time and date.
307: .El
308: .Sh FILES
309: .Bl -tag -width /usr/mdec/biosbootxx -compact
310: .It Pa /usr/mdec/biosboot
311: first stage bootstrap
312: .It Pa /usr/mdec/pxeboot
313: PXE bootstrap
314: .It Pa /boot
315: system bootstrap
316: .It Pa /etc/boot.conf
317: system bootstrap's startup file
318: .It Pa /bsd
319: kernel image
320: .It Pa /bsd.mp
321: kernel image for multiprocessor machines
322: .It Pa /bsd.rd
323: kernel image for installation/recovery
324: .El
325: .Sh EXAMPLES
326: Boot the default kernel:
327: .Pp
328: .Dl boot> boot
329: .Pp
330: Remove the 5 second pause at boot-time permanently, causing
331: .Nm
332: to load the kernel immediately without prompting:
333: .Pp
334: .Dl # echo \&"boot\&" > /etc/boot.conf
335: .Pp
336: Use serial console.
337: A null modem cable should connect the specified serial port to a terminal.
338: Useful for debugging.
339: .Pp
340: .Dl boot> set tty com0
341: .Pp
342: Invoke the serial console at every boot:
343: .Pp
344: .Dl # echo \&"set tty com0\&" > /etc/boot.conf
345: .Pp
346: Boot the kernel named
347: .Pa /bsd
348: from the second hard disk in
349: .Dq User Kernel Configuration
350: mode (see
351: .Xr boot_config 8 ) .
352: This mechanism allows for the explicit enabling and disabling of devices
353: during the current boot sequence, as well as the modification
354: of device parameters.
355: Once booted, such changes can be made permanent by using
356: .Xr config 8 Ns 's
357: .Fl e
358: option.
359: .Pp
360: .Dl boot> boot hd1a:/bsd -c
361: .Sh SEE ALSO
362: .Xr gzip 1 ,
363: .Xr autoconf 4 ,
364: .Xr ddb 4 ,
365: .Xr biosboot 8 ,
366: .Xr boot_config 8 ,
367: .Xr boot_i386 8 ,
368: .Xr fdisk 8 ,
369: .Xr installboot 8 ,
370: .Xr pxeboot 8 ,
371: .Xr reboot 8
372: .Pp
373: RFC 1950 describes the zlib library interface.
374: .Pp
375: The official home page for the version of zlib used in this
376: operating system is at http://www.gzip.org/zlib/.
377: .Sh HISTORY
378: This program was written by Michael Shalayeff for
379: .Ox 2.1 .
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