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 1.11 2006/02/28 02:25:11 swildner 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;/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 kern.emergency_intr_enable
428 Setting this to 1 enables emergency interrupt polling. All interrupt
429 handlers are executed periodically. This mode is very expensive and should
430 only be used to get a system accessible when interrupt routing is
431 otherwise broken. It is primarly used by kernel developers to debug new
433 .It Va kern.emergency_intr_freq
434 Set the polling rate for the emergency interrupt polling code. The
435 default is 10 (hz) to dissuade casual use. If you are doing real work
436 with emergency interrupt polling mode enabled, it is recommended
437 that you use a frequency between 100hz and 300hz.
439 Set the size of a number of statically allocated system tables; see
441 for a description of how to select an appropriate value for this
443 When set, this tunable replaces the value declared in the kernel
444 compile-time configuration file.
445 .It Va kern.ipc.nmbclusters
446 Set the number of mbuf clusters to be allocated.
447 The value cannot be set below the default
448 determined when the kernel was compiled.
451 .It Va kern.ipc.nsfbufs
454 buffers to be allocated.
458 Toggles the mmx optimizations for the bcopy/copyin/copyout routines
459 .It Va kern.vm.kmem.size
460 Sets the size of kernel memory (bytes).
461 This overrides the value determined when the kernel was compiled.
464 .It Va kern.maxswzone
465 Limits the amount of KVM to be used to hold swap
466 meta information, which directly governs the
467 maximum amount of swap the system can support.
468 This value is specified in bytes of KVA space
469 and defaults to around 70MBytes.
471 to not reduce this value such that the actual
472 amount of configured swap exceeds \(12 the
473 kernel-supported swap.
474 The default 70MB allows
475 the kernel to support a maximum of (approximately)
476 14GB of configured swap.
477 Only mess around with
478 this parameter if you need to greatly extend the
479 KVM reservation for other resources such as the
483 .Va VM_SWZONE_SIZE_MAX .
484 .It Va kern.maxbcache
485 Limits the amount of KVM reserved for use by the
486 buffer cache, specified in bytes.
487 The default maximum is 200MB.
488 This parameter is used to
489 prevent the buffer cache from eating too much
490 KVM in large-memory machine configurations.
491 Only mess around with this parameter if you need to
492 greatly extend the KVM reservation for other resources
493 such as the swap zone or
496 the NBUF parameter will override this limit.
498 .Va VM_BCACHE_SIZE_MAX .
499 .It Va machdep.disable_mtrrs
500 Disable the use of i686 MTRRs (x86 only).
501 .It Va net.inet.tcp.tcbhashsize
502 Overrides the compile-time set value of
504 or the preset default of 512.
505 Must be a power of 2.
508 When a builtin command is executed, the rest of the line is taken
509 by it as arguments, and it is processed by a special parser which
510 is not used for regular Forth commands.
512 This special parser applies the following rules to the parsed text:
516 All backslash characters are preprocessed.
519 \eb , \ef , \er , \en and \et are processed as in C.
521 \es is converted to a space.
528 Useful for things like
531 \e0xN and \e0xNN are replaced by the hex N or NN.
533 \eNNN is replaced by the octal NNN
537 \e" , \e' and \e$ will escape these characters, preventing them from
538 receiving special treatment in Step 2, described below.
540 \e\e will be replaced with a single \e .
542 In any other occurrence, backslash will just be removed.
545 Every string between non-escaped quotes or double-quotes will be treated
546 as a single word for the purposes of the remaining steps.
552 with the value of the environment variable
555 Space-delimited arguments are passed to the called builtin command.
556 Spaces can also be escaped through the use of \e\e .
559 An exception to this parsing rule exists, and is described in
560 .Sx BUILTINS AND FORTH .
561 .Ss BUILTINS AND FORTH
562 All builtin words are state-smart, immediate words.
563 If interpreted, they behave exactly as described previously.
564 If they are compiled, though,
565 they extract their arguments from the stack instead of the command line.
567 If compiled, the builtin words expect to find, at execution time, the
568 following parameters on the stack:
569 .D1 Ar addrN lenN ... addr2 len2 addr1 len1 N
572 are strings which will compose the command line that will be parsed
573 into the builtin's arguments.
574 Internally, these strings are concatenated in from 1 to N,
575 with a space put between each one.
577 If no arguments are passed, a 0
579 be passed, even if the builtin accepts no arguments.
581 While this behavior has benefits, it has its trade-offs.
582 If the execution token of a builtin is acquired (through
590 the builtin behavior will depend on the system state
598 \&! This is particularly annoying for programs that want or need to
600 In this case, the use of a proxy is recommended.
605 is a Forth interpreter written in C, in the form of a forth
606 virtual machine library that can be called by C functions and vice
611 each line read interactively is then fed to
615 back to execute the builtin words.
622 The words available to
624 can be classified into four groups.
627 Forth standard words, extra
631 words, and the builtin commands;
632 the latter were already described.
635 Forth standard words are listed in the
638 The words falling in the two other groups are described in the
639 following subsections.
641 .Bl -tag -width wid-set-super
649 This is the STRING word set's
656 This is the STRING word set's
666 .Ss FREEBSD EXTRA WORDS
667 .Bl -tag -width XXXXXXXX
669 Evaluates the remainder of the input buffer, after having printed it first.
671 Evaluates the remainder of the input buffer under a
677 but without outputting a trailing space.
678 .It Ic fclose Pq Ar fd --
680 .It Ic fkey Pq Ar fd -- char
681 Reads a single character from a file.
682 .It Ic fload Pq Ar fd --
685 .It Ic fopen Pq Ar addr len mode Li -- Ar fd
687 Returns a file descriptor, or \-1 in case of failure.
690 parameter selects whether the file is to be opened for read access, write
693 .Dv O_RDONLY , O_WRONLY ,
697 .Pa /boot/support.4th ,
698 indicating read only, write only, and read-write access, respectively.
701 .Pq Ar fd addr len -- len'
709 Returns the actual number of bytes read, or -1 in case of error or end of
711 .It Ic heap? Pq -- Ar cells
712 Return the space remaining in the dictionary heap, in cells.
713 This is not related to the heap used by dynamic memory allocation words.
714 .It Ic inb Pq Ar port -- char
715 Reads a byte from a port.
716 .It Ic key Pq -- Ar char
717 Reads a single character from the console.
718 .It Ic key? Pq -- Ar flag
721 if there is a character available to be read from the console.
726 .It Ic outb Pq Ar port char --
727 Writes a byte to a port.
728 .It Ic seconds Pq -- Ar u
729 Returns the number of seconds since midnight.
730 .It Ic tib> Pq -- Ar addr len
731 Returns the remainder of the input buffer as a string on the stack.
732 .It Ic trace! Pq Ar flag --
733 Activates or deactivates tracing.
737 .Ss FREEBSD DEFINED ENVIRONMENTAL QUERIES
741 if the architecture is IA32.
742 .It DragonFly_version
744 version at compile time.
749 .Ss SYSTEM DOCUMENTATION
751 .Bl -tag -width /boot/defaults/loader.conf -compact
755 .It Pa /boot/boot.4th
759 .It Pa /boot/boot.conf
761 bootstrapping script.
763 .It Pa /boot/defaults/loader.conf
764 .It Pa /boot/loader.conf
765 .It Pa /boot/loader.conf.local
767 configuration files, as described in
769 .It Pa /boot/loader.rc
771 bootstrapping script.
772 .It Pa /boot/loader.help
775 Contains the help messages.
778 Boot in single user mode:
782 Load kernel's user configuration file.
783 Notice that a kernel must be loaded before any other
785 command is attempted.
786 .Bd -literal -offset indent
788 load -t userconfig_script /boot/kernel.conf
791 Load the kernel, a splash screen, and then autoboot in five seconds.
792 .Bd -literal -offset indent
795 load -t splash_image_data /boot/chuckrulez.bmp
799 Set the disk unit of the root device to 2, and then boot.
800 This would be needed in a system with two IDE disks,
801 with the second IDE disk hardwired to wd2 instead of wd1.
802 .Bd -literal -offset indent
808 .Bl -tag -width /usr/share/examples/bootforth/X
809 .It Pa /boot/loader.4th
810 Extra builtin-like words.
811 .It Pa /boot/support.4th
814 .It Pa /usr/share/examples/bootforth/
818 The following values are thrown by
820 .Bl -tag -width XXXXX -offset indent
822 Any type of error in the processing of a builtin.
833 Out of interpreting text.
835 Need more text to succeed -- will finish on next run.
849 For the purposes of ANS Forth compliance, loader is an
851 ANS Forth System with Environmental Restrictions, Providing
857 parse, pick, roll, refill, to, value, \e, false, true,
860 compile\&, , erase, nip, tuck
865 from the Core Extensions word set, Providing the Exception Extensions
866 word set, Providing the Locals Extensions word set, Providing the
867 Memory-Allocation Extensions word set, Providing
871 bye, forget, see, words,
878 from the Programming-Tools extension word set, Providing the
879 Search-Order extensions word set.
891 .An Michael Smith Aq msmith@FreeBSD.org .
895 .An John Sadler Aq john_sadler@alum.mit.edu .
901 words will read from the input buffer instead of the console.
902 The latter will be fixed, but the former will not.
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