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 1.19 2008/07/11 23:42:46 thomas 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.
157 Flags are described in
161 The behavior of this builtin is changed if
169 Displays text on the screen.
170 A new line will be printed unless
175 Displays memory usage statistics.
176 For debugging purposes only.
178 .It Ic help Op topic Op subtopic
179 Shows help messages read from
180 .Pa /boot/loader.help .
183 will list the topics available.
185 .It Ic include Ar file Op Ar
186 Process script files.
187 Each file, in turn, is completely read into memory,
188 and then each of its lines is passed to the command line interpreter.
189 If any error is returned by the interpreter, the include
190 command aborts immediately, without reading any other files, and
191 returns an error itself (see
198 Loads a kernel, kernel loadable module (kld), or file of opaque
199 contents tagged as being of the type
201 Kernel and modules can be either in a.out or ELF format.
202 Any arguments passed after the name of the file to be loaded
203 will be passed as arguments to that file.
204 Currently, argument passing does not work for the kernel.
210 Displays a listing of files in the directory
212 or the root directory if
217 is specified, file sizes will be shown too.
220 Lists all of the devices from which it may be possible to load modules.
223 is specified, more details are printed.
226 Displays loaded modules.
229 is specified, more details are shown.
231 .It Ic more Ar file Op Ar
232 Display the files specified, with a pause at each
236 .It Ic pnpscan Op Fl v
237 Scans for Plug-and-Play devices.
238 This is not functional at present.
245 Reads a line of input from the terminal, storing it in
248 A timeout can be specified with
250 though it will be canceled at the first key pressed.
251 A prompt may also be displayed through the
256 Immediately reboots the system.
258 .It Ic set Ar variable
259 .It Ic set Ar variable Ns = Ns Ar value
260 Set loader's environment variables.
262 .It Ic show Op Va variable
263 Displays the specified variable's value, or all variables and their
269 Remove all modules from memory.
271 .It Ic unset Va variable
274 from the environment.
280 .Ss BUILTIN ENVIRONMENT VARIABLES
283 has actually two different kinds of
286 There are ANS Forth's
287 .Em environmental queries ,
288 and a separate space of environment variables used by builtins, which
289 are not directly available to Forth words.
290 It is the latter type that this section covers.
292 Environment variables can be set and unset through the
296 builtins, and can have their values interactively examined through the
300 Their values can also be accessed as described in
303 Notice that these environment variables are not inherited by any shell
304 after the system has been booted.
306 A few variables are set automatically by
308 Others can affect the behavior of either
310 or the kernel at boot.
311 Some options may require a value,
312 while others define behavior just by being set.
313 Both types of builtin variables are described below.
314 .Bl -tag -width bootfile
316 Unset this to disable automatic loading of the ACPI module.
317 .It Va autoboot_delay
320 will wait before booting.
321 If this variable is not defined,
323 will default to 10 seconds.
329 will be automatically attempted after processing
330 .Pa /boot/loader.rc ,
333 will be processed normally, defaulting to 10 seconds delay.
335 Instructs the kernel to prompt the user for the name of the root device
336 when the kernel is booted.
338 Instructs the kernel to start in the DDB debugger, rather than
339 proceeding to initialize when booted.
341 Selects gdb-remote mode for the kernel debugger by default.
343 Prevents the kernel from initiating a multi-user startup; instead single-user
344 mode will be entered when the kernel has finished device probing.
345 .It Va boot_userconfig
346 Requests that the kernel's interactive device configuration program
347 be run when the kernel is booted.
349 Setting this variable causes extra debugging information to be printed
350 by the kernel during the boot phase.
352 List of semicolon-separated search path for bootable kernels.
354 .Dq Li kernel;kernel.old .
356 Defines the current console.
358 Selects the default device.
359 Syntax for devices is odd.
361 Sets the list of binaries which the kernel will try to run as the initial
363 The first matching binary is used.
365 .Dq Li /sbin/init:/sbin/oinit:/sbin/init.bak .
369 if the Forth's current state is interpreting.
371 Define the number of lines on the screen, to be used by the pager.
373 Sets the list of directories which will be searched for modules
374 named in a load command or implicitly required by a dependency.
375 The default value for this variable is
376 .Dq Li /;/boot;/modules .
378 Sets the number of IDE disks as a workaround for some problems in
379 finding the root disk at boot.
380 This has been deprecated in favor of
387 .Dq Li "\e${interpret}" .
388 .It Va root_disk_unit
389 If the code which detects the disk unit number for the root disk is
390 confused, e.g. by a mix of SCSI and IDE disks, or IDE disks with
391 gaps in the sequence (e.g. no primary slave), the unit number can
392 be forced by setting this variable.
394 By default the value of
396 is used to set the root file system
397 when the kernel is booted.
398 This can be overridden by setting
402 The name of a device where the kernel can save a crash dump in case
404 This automatically sets the
410 Other variables are used to override kernel tunable parameters.
413 tunables are available:
416 Limit the amount of physical memory the system will use.
417 By default the size is in bytes, but the
418 .Cm k , K , m , M , g
422 are also accepted and indicate kilobytes, megabytes and gigabytes
424 An invalid suffix will result in the variable being ignored by the
426 .It Va kern.emergency_intr_enable
427 Setting this to 1 enables emergency interrupt polling. All interrupt
428 handlers are executed periodically. This mode is very expensive and should
429 only be used to get a system accessible when interrupt routing is
430 otherwise broken. It is primarily used by kernel developers to debug new
432 .It Va kern.emergency_intr_freq
433 Set the polling rate for the emergency interrupt polling code. The
434 default is 10 (hz) to dissuade casual use. If you are doing real work
435 with emergency interrupt polling mode enabled, it is recommended
436 that you use a frequency between 100hz and 300hz.
438 Set the size of a number of statically allocated system tables; see
440 for a description of how to select an appropriate value for this
442 When set, this tunable replaces the value declared in the kernel
443 compile-time configuration file.
444 .It Va kern.ipc.nmbclusters
445 Set the number of mbuf clusters to be allocated.
446 The value cannot be set below the default
447 determined when the kernel was compiled.
450 .It Va kern.ipc.nsfbufs
453 buffers to be allocated.
457 Toggles the mmx optimizations for the bcopy/copyin/copyout routines
458 .It Va kern.vm.kmem.size
459 Sets the size of kernel memory (bytes).
460 This overrides the value determined when the kernel was compiled.
461 .It Va kern.maxswzone
462 Limits the amount of KVM to be used to hold swap
463 meta information, which directly governs the
464 maximum amount of swap the system can support.
465 This value is specified in bytes of KVA space
466 and defaults to around 70MBytes.
468 to not reduce this value such that the actual
469 amount of configured swap exceeds \(12 the
470 kernel-supported swap.
471 The default 70MB allows
472 the kernel to support a maximum of (approximately)
473 14GB of configured swap.
474 Only mess around with
475 this parameter if you need to greatly extend the
476 KVM reservation for other resources such as the
480 .Va VM_SWZONE_SIZE_MAX .
481 .It Va kern.maxbcache
482 Limits the amount of KVM reserved for use by the
483 buffer cache, specified in bytes.
484 The default maximum is 200MB.
485 This parameter is used to
486 prevent the buffer cache from eating too much
487 KVM in large-memory machine configurations.
488 Only mess around with this parameter if you need to
489 greatly extend the KVM reservation for other resources
490 such as the swap zone or
493 the NBUF parameter will override this limit.
495 .Va VM_BCACHE_SIZE_MAX .
496 .It Va machdep.disable_mtrrs
497 Disable the use of i686 MTRRs (x86 only).
498 .It Va net.inet.tcp.tcbhashsize
499 Overrides the compile-time set value of
501 or the preset default of 512.
502 Must be a power of 2.
505 When a builtin command is executed, the rest of the line is taken
506 by it as arguments, and it is processed by a special parser which
507 is not used for regular Forth commands.
509 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.
598 .Dl : (boot) boot \&;
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 DRAGONFLY 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 DRAGONFLY DEFINED ENVIRONMENTAL QUERIES
737 if the architecture is IA32.
738 .It DragonFly_version
740 version at compile time.
745 .Ss SYSTEM DOCUMENTATION
747 .Bl -tag -width /boot/defaults/loader.conf -compact
751 .It Pa /boot/boot.4th
755 .It Pa /boot/boot.conf
757 bootstrapping script.
759 .It Pa /boot/defaults/loader.conf
760 .It Pa /boot/loader.conf
761 .It Pa /boot/loader.conf.local
763 configuration files, as described in
765 .It Pa /boot/loader.rc
767 bootstrapping script.
768 .It Pa /boot/loader.help
771 Contains the help messages.
774 Boot in single user mode:
778 Load kernel's user configuration file.
779 Notice that a kernel must be loaded before any other
781 command is attempted.
782 .Bd -literal -offset indent
784 load -t userconfig_script /boot/kernel.conf
787 Load the kernel, a splash screen, and then autoboot in five seconds.
788 .Bd -literal -offset indent
791 load -t splash_image_data /boot/chuckrulez.bmp
795 Set the disk unit of the root device to 2, and then boot.
796 This would be needed in a system with two IDE disks,
797 with the second IDE disk hardwired to wd2 instead of wd1.
798 .Bd -literal -offset indent
804 .Bl -tag -width /usr/share/examples/bootforth/X
805 .It Pa /boot/loader.4th
806 Extra builtin-like words.
807 .It Pa /boot/support.4th
810 .It Pa /usr/share/examples/bootforth/
814 The following values are thrown by
816 .Bl -tag -width XXXXX -offset indent
818 Any type of error in the processing of a builtin.
829 Out of interpreting text.
831 Need more text to succeed -- will finish on next run.
847 For the purposes of ANS Forth compliance, loader is an
849 ANS Forth System with Environmental Restrictions, Providing
855 parse, pick, roll, refill, to, value, \e, false, true,
858 compile\&, , erase, nip, tuck
863 from the Core Extensions word set, Providing the Exception Extensions
864 word set, Providing the Locals Extensions word set, Providing the
865 Memory-Allocation Extensions word set, Providing
869 bye, forget, see, words,
876 from the Programming-Tools extension word set, Providing the
877 Search-Order extensions word set.
889 .An Michael Smith Aq msmith@FreeBSD.org .
893 .An John Sadler Aq john_sadler@alum.mit.edu .
899 words will read from the input buffer instead of the console.
900 The latter will be fixed, but the former will not.
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