1 .\" Copyright (c) 1999 Daniel C. Sobral
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25 .\" $FreeBSD: src/sys/boot/common/loader.8,v 1.57 2003/06/29 20:57:55 brueffer Exp $
26 .\" $DragonFly: src/sys/boot/common/loader.8,v 1.4 2003/11/10 06:08:31 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 is 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 is 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.
120 builtin commands take parameters from the command line.
122 the only way to call them from a script is by using
125 If an error condition occurs, an exception will be generated,
126 which can be intercepted using
128 Forth exception handling
130 If not intercepted, an error message will be displayed and
131 the interpreter's state will be reset, emptying the stack and restoring
134 The builtin commands available are:
136 .Bl -tag -width Ds -compact
137 .It Ic autoboot Op Ar seconds
138 Proceeds to bootstrap the system after a number of seconds, if not
139 interrupted by the user.
140 Displays a countdown prompt
141 warning the user the system is about to be booted,
142 unless interrupted by a key press.
143 The kernel will be loaded first if necessary.
144 Defaults to 10 seconds.
147 Displays statistics about disk cache usage.
151 .It Ic boot Ar kernelname Op Cm ...
152 .It Ic boot Fl flag Cm ...
153 Immediately proceeds to bootstrap the system, loading the kernel
155 Any flags or arguments are passed to the kernel, but they
156 must precede the kernel name, if a kernel name is provided.
159 The behavior of this builtin is changed if
167 Displays text on the screen.
168 A new line will be printed unless
173 Displays memory usage statistics.
174 For debugging purposes only.
176 .It Ic help Op topic Op subtopic
177 Shows help messages read from
178 .Pa /boot/loader.help .
181 will list the topics available.
183 .It Ic include Ar file Op Ar
184 Process script files.
185 Each file, in turn, is completely read into memory,
186 and then each of its lines is passed to the command line interpreter.
187 If any error is returned by the interpreter, the include
188 command aborts immediately, without reading any other files, and
189 returns an error itself (see
196 Loads a kernel, kernel loadable module (kld), or file of opaque
197 contents tagged as being of the type
199 Kernel and modules can be either in a.out or ELF format.
200 Any arguments passed after the name of the file to be loaded
201 will be passed as arguments to that file.
202 Currently, argument passing does not work for the kernel.
208 Displays a listing of files in the directory
210 or the root directory if
215 is specified, file sizes will be shown too.
218 Lists all of the devices from which it may be possible to load modules.
221 is specified, more details are printed.
224 Displays loaded modules.
227 is specified, more details are shown.
229 .It Ic more Ar file Op Ar
230 Display the files specified, with a pause at each
234 .It Ic pnpscan Op Fl v
235 Scans for Plug-and-Play devices.
236 This is not functional at present.
243 Reads a line of input from the terminal, storing it in
246 A timeout can be specified with
248 though it will be canceled at the first key pressed.
249 A prompt may also be displayed through the
254 Immediately reboots the system.
256 .It Ic set Ar variable
257 .It Ic set Ar variable Ns = Ns Ar value
258 Set loader's environment variables.
260 .It Ic show Op Va variable
261 Displays the specified variable's value, or all variables and their
267 Remove all modules from memory.
269 .It Ic unset Va variable
272 from the environment.
279 .Ss BUILTIN ENVIRONMENT VARIABLES
282 has actually two different kinds of
285 There are ANS Forth's
286 .Em environmental queries ,
287 and a separate space of environment variables used by builtins, which
288 are not directly available to Forth words.
289 It is the latter type that this section covers.
291 Environment variables can be set and unset through the
295 builtins, and can have their values interactively examined through the
299 Their values can also be accessed as described in
302 Notice that these environment variables are not inherited by any shell
303 after the system has been booted.
305 A few variables are set automatically by
307 Others can affect the behavior of either
309 or the kernel at boot.
310 Some options may require a value,
311 while others define behavior just by being set.
312 Both types of builtin variables are described below.
313 .Bl -tag -width bootfile
315 Unset this to disable automatic loading of the ACPI module.
317 .Va hint.acpi.0.disabled
320 .It Va autoboot_delay
323 will wait before booting.
324 If this variable is not defined,
326 will default to 10 seconds.
332 will be automatically attempted after processing
333 .Pa /boot/loader.rc ,
336 will be processed normally, defaulting to 10 seconds delay.
338 Instructs the kernel to prompt the user for the name of the root device
339 when the kernel is booted.
341 Instructs the kernel to start in the DDB debugger, rather than
342 proceeding to initialize when booted.
344 Selects gdb-remote mode for the kernel debugger by default.
346 Prevents the kernel from initiating a multi-user startup; instead single-user
347 mode will be entered when the kernel has finished device probing.
348 .It Va boot_userconfig
349 Requests that the kernel's interactive device configuration program
350 be run when the kernel is booted.
352 Setting this variable causes extra debugging information to be printed
353 by the kernel during the boot phase.
355 List of semicolon-separated search path for bootable kernels.
357 .Dq Li kernel;kernel.old .
359 Defines the current console.
361 Selects the default device.
362 Syntax for devices is odd.
364 Sets the list of binaries which the kernel will try to run as the initial
366 The first matching binary is used.
368 .Dq Li /sbin/init:/sbin/oinit:/sbin/init.bak:/stand/sysinstall .
372 if the Forth's current state is interpreting.
374 Define the number of lines on the screen, to be used by the pager.
376 Sets the list of directories which will be searched for modules
377 named in a load command or implicitly required by a dependency.
378 The default value for this variable is
379 .Dq Li /boot/kernel;/boot/modules .
381 Sets the number of IDE disks as a workaround for some problems in
382 finding the root disk at boot.
383 This has been deprecated in favor of
390 .Dq Li "${currdev}>" .
391 .It Va root_disk_unit
392 If the code which detects the disk unit number for the root disk is
393 confused, e.g. by a mix of SCSI and IDE disks, or IDE disks with
394 gaps in the sequence (e.g. no primary slave), the unit number can
395 be forced by setting this variable.
397 By default the value of
399 is used to set the root file system
400 when the kernel is booted.
401 This can be overridden by setting
405 The name of a device where the kernel can save a crash dump in case
407 This automatically sets the
413 Other variables are used to override kernel tunable parameters.
414 The following tunables are available:
417 Limit the amount of physical memory the system will use.
418 By default the size is in bytes, but the
419 .Cm k , K , m , M , g
423 are also accepted and indicate kilobytes, megabytes and gigabytes
425 An invalid suffix will result in the variable being ignored by the
427 .It Va hw.pci.enable_io_modes
428 Enable PCI resources which are left off by some BIOSes or are not
429 enabled correctly by the device driver.
430 Tunable value set to ON (1) by default, but this may cause problems
431 with some peripherals.
432 .It Va hw.pci.allow_unsupported_io_range
433 Allow the PCI bridge to pass through an unsupported memory range
434 assigned by the BIOS.
435 Tunable value set to OFF (0) by default.
437 Set the size of a number of statically allocated system tables; see
439 for a description of how to select an appropriate value for this
441 When set, this tunable replaces the value declared in the kernel
442 compile-time configuration file.
443 .It Va kern.ipc.nmbclusters
444 Set the number of mbuf clusters to be allocated.
445 The value cannot be set below the default
446 determined when the kernel was compiled.
449 .It Va kern.ipc.nsfbufs
452 buffers to be allocated.
455 .It Va kern.vm.kmem.size
456 Sets the size of kernel memory (bytes).
457 This overrides the value determined when the kernel was compiled.
460 .It Va kern.maxswzone
461 Limits the amount of KVM to be used to hold swap
462 meta information, which directly governs the
463 maximum amount of swap the system can support.
464 This value is specified in bytes of KVA space
465 and defaults to around 70MBytes.
467 to not reduce this value such that the actual
468 amount of configured swap exceeds 1/2 the
469 kernel-supported swap.
470 The default 70MB allows
471 the kernel to support a maximum of (approximately)
472 14GB of configured swap.
473 Only mess around with
474 this parameter if you need to greatly extend the
475 KVM reservation for other resources such as the
479 .Va VM_SWZONE_SIZE_MAX .
480 .It Va kern.maxbcache
481 Limits the amount of KVM reserved for use by the
482 buffer cache, specified in bytes.
483 The default maximum is 200MB.
484 This parameter is used to
485 prevent the buffer cache from eating too much
486 KVM in large-memory machine configurations.
487 Only mess around with this parameter if you need to
488 greatly extend the KVM reservation for other resources
489 such as the swap zone or
492 the NBUF parameter will override this limit.
494 .Va VM_BCACHE_SIZE_MAX .
495 .It Va machdep.disable_mtrrs
496 Disable the use of i686 MTRRs (x86 only).
497 .It Va net.inet.tcp.tcbhashsize
498 Overrides the compile-time set value of
500 or the preset default of 512.
501 Must be a power of 2.
504 When a builtin command is executed, the rest of the line is taken
505 by it as arguments, and it is processed by a special parser which
506 is not used for regular Forth commands.
508 This special parser applies the following rules to the parsed text:
512 All backslash characters are preprocessed.
515 \eb , \ef , \er , \en and \et are processed as in C.
517 \es is converted to a space.
524 Useful for things like
527 \e0xN and \e0xNN are replaced by the hex N or NN.
529 \eNNN is replaced by the octal NNN
533 \e" , \e' and \e$ will escape these characters, preventing them from
534 receiving special treatment in Step 2, described below.
536 \e\e will be replaced with a single \e .
538 In any other occurrence, backslash will just be removed.
541 Every string between non-escaped quotes or double-quotes will be treated
542 as a single word for the purposes of the remaining steps.
548 with the value of the environment variable
551 Space-delimited arguments are passed to the called builtin command.
552 Spaces can also be escaped through the use of \e\e .
555 An exception to this parsing rule exists, and is described in
556 .Sx BUILTINS AND FORTH .
557 .Ss BUILTINS AND FORTH
558 All builtin words are state-smart, immediate words.
559 If interpreted, they behave exactly as described previously.
560 If they are compiled, though,
561 they extract their arguments from the stack instead of the command line.
563 If compiled, the builtin words expect to find, at execution time, the
564 following parameters on the stack:
565 .D1 Ar addrN lenN ... addr2 len2 addr1 len1 N
568 are strings which will compose the command line that will be parsed
569 into the builtin's arguments.
570 Internally, these strings are concatenated in from 1 to N,
571 with a space put between each one.
573 If no arguments are passed, a 0
575 be passed, even if the builtin accepts no arguments.
577 While this behavior has benefits, it has its trade-offs.
578 If the execution token of a builtin is acquired (through
586 the builtin behavior will depend on the system state
594 \&! This is particularly annoying for programs that want or need to
596 In this case, the use of a proxy is recommended.
601 is a Forth interpreter written in C, in the form of a forth
602 virtual machine library that can be called by C functions and vice
607 each line read interactively is then fed to
611 back to execute the builtin words.
618 The words available to
620 can be classified into four groups.
623 Forth standard words, extra
627 words, and the builtin commands;
628 the latter were already described.
631 Forth standard words are listed in the
634 The words falling in the two other groups are described in the
635 following subsections.
637 .Bl -tag -width wid-set-super
645 This is the STRING word set's
652 This is the STRING word set's
662 .Ss FREEBSD EXTRA WORDS
663 .Bl -tag -width XXXXXXXX
665 Evaluates the remainder of the input buffer, after having printed it first.
667 Evaluates the remainder of the input buffer under a
673 but without outputting a trailing space.
674 .It Ic fclose Pq Ar fd --
676 .It Ic fkey Pq Ar fd -- char
677 Reads a single character from a file.
678 .It Ic fload Pq Ar fd --
681 .It Ic fopen Pq Ar addr len mode Li -- Ar fd
683 Returns a file descriptor, or \-1 in case of failure.
686 parameter selects whether the file is to be opened for read access, write
689 .Dv O_RDONLY , O_WRONLY ,
693 .Pa /boot/support.4th ,
694 indicating read only, write only, and read-write access, respectively.
697 .Pq Ar fd addr len -- len'
705 Returns the actual number of bytes read, or -1 in case of error or end of
707 .It Ic heap? Pq -- Ar cells
708 Return the space remaining in the dictionary heap, in cells.
709 This is not related to the heap used by dynamic memory allocation words.
710 .It Ic inb Pq Ar port -- char
711 Reads a byte from a port.
712 .It Ic key Pq -- Ar char
713 Reads a single character from the console.
714 .It Ic key? Pq -- Ar flag
717 if there is a character available to be read from the console.
722 .It Ic outb Pq Ar port char --
723 Writes a byte to a port.
724 .It Ic seconds Pq -- Ar u
725 Returns the number of seconds since midnight.
726 .It Ic tib> Pq -- Ar addr len
727 Returns the remainder of the input buffer as a string on the stack.
728 .It Ic trace! Pq Ar flag --
729 Activates or deactivates tracing.
733 .Ss FREEBSD DEFINED ENVIRONMENTAL QUERIES
737 if the architecture is IA32.
740 if the architecture is AXP.
743 version at compile time.
748 .Ss SYSTEM DOCUMENTATION
750 .Bl -tag -width /boot/defaults/loader.conf -compact
754 .It Pa /boot/boot.4th
758 .It Pa /boot/boot.conf
760 bootstrapping script.
762 .It Pa /boot/defaults/loader.conf
763 .It Pa /boot/loader.conf
764 .It Pa /boot/loader.conf.local
766 configuration files, as described in
768 .It Pa /boot/loader.rc
770 bootstrapping script.
771 .It Pa /boot/loader.help
774 Contains the help messages.
777 Boot in single user mode:
781 Load kernel's user configuration file.
782 Notice that a kernel must be loaded before any other
784 command is attempted.
785 .Bd -literal -offset indent
787 load -t userconfig_script /boot/kernel.conf
790 Load the kernel, a splash screen, and then autoboot in five seconds.
791 .Bd -literal -offset indent
794 load -t splash_image_data /boot/chuckrulez.bmp
798 Set the disk unit of the root device to 2, and then boot.
799 This would be needed in a system with two IDE disks,
800 with the second IDE disk hardwired to wd2 instead of wd1.
801 .Bd -literal -offset indent
807 .Bl -tag -width /usr/share/examples/bootforth/X
808 .It Pa /boot/loader.4th
809 Extra builtin-like words.
810 .It Pa /boot/support.4th
813 .It Pa /usr/share/examples/bootforth/
817 The following values are thrown by
819 .Bl -tag -width XXXXX -offset indent
821 Any type of error in the processing of a builtin.
832 Out of interpreting text.
834 Need more text to succeed -- will finish on next run.
848 For the purposes of ANS Forth compliance, loader is an
850 ANS Forth System with Environmental Restrictions, Providing
856 parse, pick, roll, refill, to, value, \e, false, true,
859 compile\&, , erase, nip, tuck
864 from the Core Extensions word set, Providing the Exception Extensions
865 word set, Providing the Locals Extensions word set, Providing the
866 Memory-Allocation Extensions word set, Providing
870 bye, forget, see, words,
877 from the Programming-Tools extension word set, Providing the
878 Search-Order extensions word set.
890 .An Michael Smith Aq msmith@FreeBSD.org .
894 .An John Sadler Aq john_sadler@alum.mit.edu .
900 words will read from the input buffer instead of the console.
901 The latter will be fixed, but the former will not.
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