1 .\" Copyright (c) 1999 Daniel C. Sobral
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25 .\" $FreeBSD: src/sys/boot/common/loader.8,v 1.18.2.15 2003/05/10 23:40:09 murray Exp $
26 .\" $DragonFly: src/sys/boot/common/loader.8,v 1.2 2003/06/17 04:28:16 dillon Exp $
28 .\" Note: The date here should be updated whenever a non-trivial
29 .\" change is made to the manual page.
35 .Nd kernel bootstrapping final stage
41 kernel bootstrapping process.
42 On IA32 (i386) architectures, it is a
45 It is linked statically to
47 and usually located in the directory
50 It provides a scripting language that can be used to
51 automate tasks, do pre-configuration or assist in recovery
53 This scripting language is roughly divided in
55 The smaller one is a set of commands
56 designed for direct use by the casual user, called "builtin
57 commands" for historical reasons.
58 The main drive behind these commands is user-friendliness.
59 The bigger component is an
61 Forth compatible Forth interpreter based on ficl, by
64 During initialization,
66 will probe for a console and set the
68 variable, or set it to serial console
70 if the previous boot stage used that.
71 Then, devices are probed,
80 is initialized, the builtin words are added to its vocabulary, and
82 will be processed if it exists.
83 No disk switching is possible while that file is being read.
95 is processed if available, and, failing that,
97 will be read for historical reasons.
98 These files are processed through the
100 command, which reads all of them into memory before processing them,
101 making disk changes possible.
105 has not been tried, and if
109 (not case sensitive), then an
112 If the system gets past this point,
116 will engage interactive mode.
119 builtin commands take its parameters from the command line.
121 the only way to call them from a script is by using
124 If an error condition occurs, an exception will be generated,
125 which can be intercepted using
127 Forth exception handling
129 If not intercepted, an error message will be displayed and
130 the interpreter's state will be reset, emptying the stack and restoring
133 The builtin commands available are:
135 .Bl -tag -width Ds -compact
136 .It Ic autoboot Op Ar seconds
137 Proceeds to bootstrap the system after a number of seconds, if not
138 interrupted by the user.
139 Displays a countdown prompt
140 warning the user the system is about to be booted,
141 unless interrupted by a key press.
142 The kernel will be loaded first if necessary.
143 Defaults to 10 seconds.
146 Displays statistics about disk cache usage.
150 .It Ic boot Ar kernelname Op Cm ...
151 .It Ic boot Fl flag Cm ...
152 Immediately proceeds to bootstrap the system, loading the kernel
154 Any flags or arguments are passed to the kernel, but they
155 must precede the kernel name, if a kernel name is provided.
158 The behavior of this builtin is changed if
166 Displays text on the screen.
167 A new line will be printed unless
172 Displays memory usage statistics.
173 For debugging purposes only.
175 .It Ic help Op topic Op subtopic
176 Shows help messages read from
177 .Pa /boot/loader.help .
180 will list the topics available.
182 .It Ic include Ar file Op Ar
183 Process script files.
184 Each file, in turn, is completely read into memory,
185 and then each of its lines is passed to the command line interpreter.
186 If any error is returned by the interpreter, the include
187 command aborts immediately, without reading any other files, and
188 returns an error itself (see
195 Loads a kernel, kernel loadable module (kld), or file of opaque
196 contents tagged as being of the type
198 Kernel and modules can be either in a.out or ELF format.
199 Any arguments passed after the name of the file to be loaded
200 will be passed as arguments to that file.
201 Currently, argument passing does not work for the kernel.
207 Displays a listing of files in the directory
209 or the root directory if
214 is specified, file sizes will be shown too.
217 Lists all of the devices from which it may be possible to load modules.
220 is specified, more details are printed.
223 Displays loaded modules.
226 is specified, more details are shown.
228 .It Ic more Ar file Op Ar
229 Display the files specified, with a pause at each
233 .It Ic pnpscan Op Fl v
234 Scans for Plug-and-Play devices.
235 This is not functional at present.
242 Reads a line of input from the terminal, storing it in
245 A timeout can be specified with
247 though it will be canceled at the first key pressed.
248 A prompt may also be displayed through the
253 Immediately reboots the system.
255 .It Ic set Ar variable
256 .It Ic set Ar variable Ns = Ns Ar value
257 Set loader's environment variables.
259 .It Ic show Op Va variable
260 Displays the specified variable's value, or all variables and their
266 Remove all modules from memory.
268 .It Ic unset Va variable
271 from the environment.
278 .Ss BUILTIN ENVIRONMENT VARIABLES
281 has actually two different kinds of
284 There are ANS Forth's
285 .Em environmental queries ,
286 and a separate space of environment variables used by builtins, which
287 are not directly available to Forth words.
288 It is the latter type that this section covers.
290 Environment variables can be set and unset through the
294 builtins, and can have their values interactively examined through the
298 Their values can also be accessed as described in
301 Notice that these environment variables are not inherited by any shell
302 after the system has been booted.
304 A few variables are set automatically by
306 Others can affect the behavior of either
308 or the kernel at boot.
309 Some options may require a value,
310 while others define behavior just by being set.
311 Both types of builtin variables are described below.
312 .Bl -tag -width bootfile
313 .It Va autoboot_delay
316 will wait before booting.
317 If this variable is not defined,
319 will default to 10 seconds.
325 will be automatically attempted after processing
326 .Pa /boot/loader.rc ,
329 will be processed normally, defaulting to 10 seconds delay.
331 Instructs the kernel to prompt the user for the name of the root device
332 when the kernel is booted.
334 Instructs the kernel to start in the DDB debugger, rather than
335 proceeding to initialize when booted.
337 Selects gdb-remote mode for the kernel debugger by default.
339 Prevents the kernel from initiating a multi-user startup; instead single-user
340 mode will be entered when the kernel has finished device probing.
341 .It Va boot_userconfig
342 Requests that the kernel's interactive device configuration program
343 be run when the kernel is booted.
345 Setting this variable causes extra debugging information to be printed
346 by the kernel during the boot phase.
348 List of semicolon-separated search path for bootable kernels.
350 .Dq Li kernel;kernel.old .
352 Defines the current console.
354 Selects the default device.
355 Syntax for devices is odd.
357 Sets the list of binaries which the kernel will try to run as the initial
359 The first matching binary is used.
361 .Dq Li /sbin/init:/sbin/oinit:/sbin/init.bak:/stand/sysinstall .
365 if the Forth's current state is interpreting.
367 Define the number of lines on the screen, to be used by the pager.
369 Sets the list of directories which will be searched for modules
370 named in a load command or implicitly required by a dependency.
371 The default value for this variable is
372 .Dq Li /;/boot;/modules .
374 Sets the number of IDE disks as a workaround for some problems in
375 finding the root disk at boot.
376 This has been deprecated in favor of
383 .Dq Li "${currdev}>" .
384 .It Va root_disk_unit
385 If the code which detects the disk unit number for the root disk is
386 confused, e.g. by a mix of SCSI and IDE disks, or IDE disks with
387 gaps in the sequence (e.g. no primary slave), the unit number can
388 be forced by setting this variable.
390 By default the value of
392 is used to set the root filesystem
393 when the kernel is booted.
394 This can be overridden by setting
398 The name of a device where the kernel can save a crash dump in case
400 This automatically sets the
406 Other variables are used to override kernel tunable parameters.
407 The following tunables are available:
410 Set the size of a number of statically allocated system tables; see
412 for a description of how to select an appropriate value for this
414 When set, this tunable replaces the value declared in the kernel
415 compile-time configuration file.
416 .It Va kern.ipc.nmbclusters
417 Set the number of mbuf clusters to be allocated.
418 The value cannot be set below the default
419 determined when the kernel was compiled.
422 .It Va kern.vm.kmem.size
423 Sets the size of kernel memory (bytes).
424 This overrides completely the value
425 determined when the kernel was compiled.
428 .It Va kern.maxswzone
429 Limits the amount of KVM to be used to hold swap
430 meta information, which directly governs the
431 maximum amount of swap the system can support.
432 This value is specified in bytes of KVA space
433 and defaults to around 70MBytes.
435 to not reduce this value such that the actual
436 amount of configured swap exceeds 1/2 the
437 kernel-supported swap.
438 The default 70MB allows
439 the kernel to support a maximum of (approximately)
440 14GB of configured swap.
441 Only mess around with
442 this parameter if you need to greatly extend the
443 KVM reservation for other resources such as the
447 .Va VM_SWZONE_SIZE_MAX .
448 .It Va kern.maxbcache
449 Limits the amount of KVM reserved for use by the
450 buffer cache, specified in bytes.
451 The default maximum is 200MB.
452 This parameter is used to
453 prevent the buffer cache from eating too much
454 KVM in large-memory machine configurations.
455 Only mess around with this parameter if you need to
456 greatly extend the KVM reservation for other resources
457 such as the swap zone or
460 the NBUF parameter will override this limit.
462 .Va VM_BCACHE_SIZE_MAX .
463 .It Va machdep.pccard.pcic_irq
464 Overrides the IRQ normally assigned to a PCCARD controller.
465 Typically the first available interrupt will be allocated,
466 which may conflict with other hardware.
467 If this value is set to 0,
468 an interrupt will not be assigned
469 and the controller will operate in polled mode only.
470 .It Va net.inet.tcp.tcbhashsize
471 Overrides the compile-time set value of
473 or the preset default of 512.
474 Must be a power of 2.
477 When a builtin command is executed, the rest of the line is taken
478 by it as arguments, and it is processed by a special parser which
479 is not used for regular Forth commands.
481 This special parser applies the following rules to the parsed text:
485 All backslash characters are preprocessed.
488 \eb , \ef , \er , \en and \et are processed as in C.
490 \es is converted to a space.
497 Useful for things like
500 \e0xN and \e0xNN are replaced by the hex N or NN.
502 \eNNN is replaced by the octal NNN
506 \e" , \e' and \e$ will escape these characters, preventing them from
507 receiving special treatment in Step 2, described below.
509 \e\e will be replaced with a single \e .
511 In any other occurrence, backslash will just be removed.
514 Every string between non-escaped quotes or double-quotes will be treated
515 as a single word for the purposes of the remaining steps.
521 with the value of the environment variable
524 Space-delimited arguments are passed to the called builtin command.
525 Spaces can also be escaped through the use of \e\e .
528 An exception to this parsing rule exists, and is described in
529 .Sx BUILTINS AND FORTH .
530 .Ss BUILTINS AND FORTH
531 All builtin words are state-smart, immediate words.
532 If interpreted, they behave exactly as described previously.
533 If they are compiled, though,
534 they extract their arguments from the stack instead of the command line.
536 If compiled, the builtin words expect to find, at execution time, the
537 following parameters on the stack:
538 .D1 Ar addrN lenN ... addr2 len2 addr1 len1 N
541 are strings which will compose the command line that will be parsed
542 into the builtin's arguments.
543 Internally, these strings are concatenated in from 1 to N,
544 with a space put between each one.
546 If no arguments are passed, a 0
548 be passed, even if the builtin accepts no arguments.
550 While this behavior has benefits, it has its trade-offs.
551 If the execution token of a builtin is acquired (through
559 the builtin behavior will depend on the system state
567 \&! This is particularly annoying for programs that want or need to
569 In this case, the use of a proxy is recommended.
574 is a Forth interpreter written in C, in the form of a forth
575 virtual machine library that can be called by C functions and vice
580 each line read interactively is then fed to
584 back to execute the builtin words.
591 The words available to
593 can be classified into four groups.
596 Forth standard words, extra
600 words, and the builtin commands;
601 the latter were already described.
604 Forth standard words are listed in the
607 The words falling in the two other groups are described in the
608 following subsections.
610 .Bl -tag -width wid-set-super
618 This is the STRING word set's
625 This is the STRING word set's
635 .Ss FREEBSD EXTRA WORDS
636 .Bl -tag -width XXXXXXXX
638 Evaluates the remainder of the input buffer, after having printed it first.
640 Evaluates the remainder of the input buffer under a
646 but without outputting a trailing space.
647 .It Ic fclose Pq Ar fd --
649 .It Ic fkey Pq Ar fd -- char
650 Reads a single character from a file.
651 .It Ic fload Pq Ar fd --
654 .It Ic fopen Pq Ar addr len -- fd
656 Returns a file descriptor, or -1 in case of failure.
659 .Pq Ar fd addr len -- len'
667 Returns the actual number of bytes read, or -1 in case of error or end of
669 .It Ic heap? Pq -- Ar cells
670 Return the space remaining in the dictionary heap, in cells.
671 This is not related to the heap used by dynamic memory allocation words.
672 .It Ic inb Pq Ar port -- char
673 Reads a byte from a port.
674 .It Ic key Pq -- Ar char
675 Reads a single character from the console.
676 .It Ic key? Pq -- Ar flag
679 if there is a character available to be read from the console.
684 .It Ic outb Pq Ar port char --
685 Writes a byte to a port.
686 .It Ic seconds Pq -- Ar u
687 Returns the number of seconds since midnight.
688 .It Ic tib> Pq -- Ar addr len
689 Returns the remainder of the input buffer as a string on the stack.
690 .It Ic trace! Pq Ar flag --
691 Activates or deactivates tracing.
695 .Ss FREEBSD DEFINED ENVIRONMENTAL QUERIES
699 if the architecture is IA32.
702 if the architecture is AXP.
705 version at compile time.
710 .Ss SYSTEM DOCUMENTATION
712 .Bl -tag -width /boot/defaults/loader.conf -compact
716 .It Pa /boot/boot.4th
720 .It Pa /boot/boot.conf
722 bootstrapping script.
724 .It Pa /boot/defaults/loader.conf
725 .It Pa /boot/loader.conf
726 .It Pa /boot/loader.conf.local
728 configuration files, as described in
730 .It Pa /boot/loader.rc
732 bootstrapping script.
733 .It Pa /boot/loader.help
736 Contains the help messages.
739 Boot in single user mode:
743 Load kernel's user configuration file.
744 Notice that a kernel must be loaded before any other
746 command is attempted.
747 .Bd -literal -offset indent
749 load -t userconfig_script /boot/kernel.conf
752 Load the kernel, a splash screen, and then autoboot in five seconds.
753 .Bd -literal -offset indent
756 load -t splash_image_data /boot/chuckrulez.bmp
760 Set the disk unit of the root device to 2, and then boot.
761 This would be needed in a system with two IDE disks,
762 with the second IDE disk hardwired to wd2 instead of wd1.
763 .Bd -literal -offset indent
769 .Bl -tag -width /usr/share/examples/bootforth/X
770 .It Pa /boot/loader.4th
771 Extra builtin-like words.
772 .It Pa /boot/support.4th
775 .It Pa /usr/share/examples/bootforth/
779 The following values are thrown by
781 .Bl -tag -width XXXXX -offset indent
783 Any type of error in the processing of a builtin.
794 Out of interpreting text.
796 Need more text to succeed -- will finish on next run.
810 For the purposes of ANS Forth compliance, loader is an
812 ANS Forth System with Environmental Restrictions, Providing
818 parse, pick, roll, refill, to, value, \e, false, true,
821 compile\&, , erase, nip, tuck
826 from the Core Extensions word set, Providing the Exception Extensions
827 word set, Providing the Locals Extensions word set, Providing the
828 Memory-Allocation Extensions word set, Providing
832 bye, forget, see, words,
839 from the Programming-Tools extension word set, Providing the
840 Search-Order extensions word set.
850 .An Michael Smith Aq msmith@FreeBSD.org .
854 .An John Sadler Aq john_sadler@alum.mit.edu .
860 words will read from the input buffer instead of the console.
861 The latter will be fixed, but the former will not.