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 1.24 2008/09/15 21:23:44 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
55 directory exist on the boot file system, then
57 is prepended to all relative file names used by
59 This makes it possible to locate all files used by
65 directory on the boot file system.
66 If boot and root are the same file systems, then files used by
70 If boot and root are different file systems, then files used by
74 on the boot file system, which is mounted as
76 on the root file system when the kernel is running.
79 provides a scripting language that can be used to
80 automate tasks, do pre-configuration or assist in recovery
82 This scripting language is roughly divided in
84 The smaller one is a set of commands
85 designed for direct use by the casual user, called "builtin
86 commands" for historical reasons.
87 The main drive behind these commands is user-friendliness.
88 The bigger component is an
90 Forth compatible Forth interpreter based on FICL, by
93 During initialization,
95 will probe for a console and set the
97 variable, or set it to serial console
99 if the previous boot stage used that.
100 Then, devices are probed,
109 is initialized, the builtin words are added to its vocabulary, and
111 is processed if it exists.
112 No disk switching is possible while that file is being read.
113 The inner interpreter
124 is processed if available, and, failing that,
126 is read for historical reasons.
127 These files are processed through the
129 command, which reads all of them into memory before processing them,
130 making disk changes possible.
134 has not been tried, and if
138 (not case sensitive), then an
141 If the system gets past this point,
145 will engage interactive mode.
149 builtin commands take parameters from the command line.
151 the only way to call them from a script is by using
154 If an error condition occurs, an exception will be generated,
155 which can be intercepted using
157 Forth exception handling
159 If not intercepted, an error message will be displayed and
160 the interpreter's state will be reset, emptying the stack and restoring
163 The builtin commands available are:
165 .Bl -tag -width Ds -compact
166 .It Ic autoboot Op Ar seconds
167 Proceeds to bootstrap the system after a number of seconds, if not
168 interrupted by the user.
169 Displays a countdown prompt
170 warning the user the system is about to be booted,
171 unless interrupted by a key press.
172 The kernel will be loaded first if necessary.
173 Defaults to 10 seconds.
176 Displays statistics about disk cache usage.
180 .It Ic boot Ar kernelname Op Cm ...
181 .It Ic boot Fl flag Cm ...
182 Immediately proceeds to bootstrap the system, loading the kernel
184 Any flags or arguments are passed to the kernel, but they
185 must precede the kernel name, if a kernel name is provided.
186 Flags are described in
190 The behavior of this builtin is changed if
198 Displays text on the screen.
199 A new line will be printed unless
204 Displays memory usage statistics.
205 For debugging purposes only.
207 .It Ic help Op topic Op subtopic
208 Shows help messages read from
212 will list the topics available.
214 .It Ic include Ar file Op Ar
215 Process script files.
216 Each file, in turn, is completely read into memory,
217 and then each of its lines is passed to the command line interpreter.
218 If any error is returned by the interpreter, the include
219 command aborts immediately, without reading any other files, and
220 returns an error itself (see
227 Loads a kernel, kernel loadable module (kld), or file of opaque
228 contents tagged as being of the type
230 Kernel and modules can be either in a.out or ELF format.
231 Any arguments passed after the name of the file to be loaded
232 will be passed as arguments to that file.
233 Currently, argument passing does not work for the kernel.
239 Displays a listing of files in the directory
241 or the root directory if
246 is specified, file sizes will be shown too.
249 Lists all of the devices from which it may be possible to load modules.
252 is specified, more details are printed.
255 Displays loaded modules.
258 is specified, more details are shown.
260 .It Ic more Ar file Op Ar
261 Display the files specified, with a pause at each
265 .It Ic pnpscan Op Fl v
266 Scans for Plug-and-Play devices.
267 This is not functional at present.
274 Reads a line of input from the terminal, storing it in
277 A timeout can be specified with
279 though it will be canceled at the first key pressed.
280 A prompt may also be displayed through the
285 Immediately reboots the system.
287 .It Ic set Ar variable
288 .It Ic set Ar variable Ns = Ns Ar value
289 Set loader's environment variables.
291 .It Ic show Op Va variable
292 Displays the specified variable's value, or all variables and their
298 Remove all modules from memory.
300 .It Ic unset Va variable
303 from the environment.
309 .Ss BUILTIN ENVIRONMENT VARIABLES
312 has actually two different kinds of
315 There are ANS Forth's
316 .Em environmental queries ,
317 and a separate space of environment variables used by builtins, which
318 are not directly available to Forth words.
319 It is the latter type that this section covers.
321 Environment variables can be set and unset through the
325 builtins, and can have their values interactively examined through the
329 Their values can also be accessed as described in
332 Notice that these environment variables are not inherited by any shell
333 after the system has been booted.
335 A few variables are set automatically by
337 Others can affect the behavior of either
339 or the kernel at boot.
340 Some options may require a value,
341 while others define behavior just by being set.
342 Both types of builtin variables are described below.
343 .Bl -tag -width bootfile
345 Unset this to disable automatic loading of the ACPI module.
346 .It Va autoboot_delay
349 will wait before booting.
350 If this variable is not defined,
352 will default to 10 seconds.
358 will be automatically attempted after processing
362 will be processed normally, defaulting to 10 seconds delay.
364 Instructs the kernel to prompt the user for the name of the root device
365 when the kernel is booted.
367 Instructs the kernel to start in the DDB debugger, rather than
368 proceeding to initialize when booted.
370 Selects gdb-remote mode for the kernel debugger by default.
372 Prevents the kernel from initiating a multi-user startup; instead single-user
373 mode will be entered when the kernel has finished device probing.
374 .It Va boot_userconfig
375 Requests that the kernel's interactive device configuration program
376 be run when the kernel is booted.
378 Setting this variable causes extra debugging information to be printed
379 by the kernel during the boot phase.
381 List of semicolon-separated search path for bootable kernels.
383 .Dq Li kernel;kernel.old .
385 Defines the current console.
387 Selects the default device.
388 Syntax for devices is odd.
390 Sets the list of binaries which the kernel will try to run as the initial
392 The first matching binary is used.
394 .Dq Li /sbin/init:/sbin/oinit:/sbin/init.bak .
398 if the Forth's current state is interpreting.
400 Define the number of lines on the screen, to be used by the pager.
402 Sets the list of directories which will be searched for modules
403 named in a load command or implicitly required by a dependency.
404 The default value for this variable is
405 .Dq Li /boot;/boot/modules;/;/modules .
407 Sets the number of IDE disks as a workaround for some problems in
408 finding the root disk at boot.
409 This has been deprecated in favor of
416 .Dq Li "\e${interpret}" .
417 .It Va root_disk_unit
418 If the code which detects the disk unit number for the root disk is
419 confused, e.g. by a mix of SCSI and IDE disks, or IDE disks with
420 gaps in the sequence (e.g. no primary slave), the unit number can
421 be forced by setting this variable.
423 By default the value of
425 is used to set the root file system
426 when the kernel is booted.
427 This can be overridden by setting
431 The name of a device where the kernel can save a crash dump in case
433 This automatically sets the
439 Other variables are used to override kernel tunable parameters.
442 tunables are available:
445 Limit the amount of physical memory the system will use.
446 By default the size is in bytes, but the
447 .Cm k , K , m , M , g
451 are also accepted and indicate kilobytes, megabytes and gigabytes
453 An invalid suffix will result in the variable being ignored by the
455 .It Va hw.usb.hack_defer_exploration
456 The USB keyboard will sometimes not attach properly unless you set this
458 .It Va kern.emergency_intr_enable
459 Setting this to 1 enables emergency interrupt polling. All interrupt
460 handlers are executed periodically. This mode is very expensive and should
461 only be used to get a system accessible when interrupt routing is
462 otherwise broken. It is primarily used by kernel developers to debug new
464 .It Va kern.emergency_intr_freq
465 Set the polling rate for the emergency interrupt polling code. The
466 default is 10 (hz) to dissuade casual use. If you are doing real work
467 with emergency interrupt polling mode enabled, it is recommended
468 that you use a frequency between 100hz and 300hz.
470 Set the size of a number of statically allocated system tables; see
472 for a description of how to select an appropriate value for this
474 When set, this tunable replaces the value declared in the kernel
475 compile-time configuration file.
476 .It Va kern.ipc.nmbclusters
477 Set the number of mbuf clusters to be allocated.
478 The value cannot be set below the default
479 determined when the kernel was compiled.
482 .It Va kern.ipc.nsfbufs
485 buffers to be allocated.
489 Toggles the mmx optimizations for the bcopy/copyin/copyout routines
490 .It Va kern.vm.kmem.size
491 Sets the size of kernel memory (bytes).
492 This overrides the value determined when the kernel was compiled.
493 .It Va kern.maxswzone
494 Limits the amount of KVM to be used to hold swap
495 meta information, which directly governs the
496 maximum amount of swap the system can support.
497 This value is specified in bytes of KVA space
498 and defaults to around 70MBytes.
500 to not reduce this value such that the actual
501 amount of configured swap exceeds \(12 the
502 kernel-supported swap.
503 The default 70MB allows
504 the kernel to support a maximum of (approximately)
505 14GB of configured swap.
506 Only mess around with
507 this parameter if you need to greatly extend the
508 KVM reservation for other resources such as the
512 .Va VM_SWZONE_SIZE_MAX .
513 .It Va kern.maxbcache
514 Limits the amount of KVM reserved for use by the
515 buffer cache, specified in bytes.
516 The default maximum is 200MB.
517 This parameter is used to
518 prevent the buffer cache from eating too much
519 KVM in large-memory machine configurations.
520 Only mess around with this parameter if you need to
521 greatly extend the KVM reservation for other resources
522 such as the swap zone or
525 the NBUF parameter will override this limit.
527 .Va VM_BCACHE_SIZE_MAX .
528 .It Va machdep.disable_mtrrs
529 Disable the use of i686 MTRRs (x86 only).
530 .It Va net.inet.tcp.tcbhashsize
531 Overrides the compile-time set value of
533 or the preset default of 512.
534 Must be a power of 2.
535 .It Va vfs.root.mountfrom
536 File system type and partition, separated by colon,
537 for kernel root file system.
538 Used with boot-only partition, which is typically mounted on root file system as
540 Example: "hammer:da8s1a"
543 When a builtin command is executed, the rest of the line is taken
544 by it as arguments, and it is processed by a special parser which
545 is not used for regular Forth commands.
547 This special parser applies the following rules to the parsed text:
550 All backslash characters are preprocessed.
553 \eb , \ef , \er , \en and \et are processed as in C.
555 \es is converted to a space.
562 Useful for things like
565 \e0xN and \e0xNN are replaced by the hex N or NN.
567 \eNNN is replaced by the octal NNN
571 \e" , \e' and \e$ will escape these characters, preventing them from
572 receiving special treatment in Step 2, described below.
574 \e\e will be replaced with a single \e .
576 In any other occurrence, backslash will just be removed.
579 Every string between non-escaped quotes or double-quotes will be treated
580 as a single word for the purposes of the remaining steps.
586 with the value of the environment variable
589 Space-delimited arguments are passed to the called builtin command.
590 Spaces can also be escaped through the use of \e\e .
593 An exception to this parsing rule exists, and is described in
594 .Sx BUILTINS AND FORTH .
595 .Ss BUILTINS AND FORTH
596 All builtin words are state-smart, immediate words.
597 If interpreted, they behave exactly as described previously.
598 If they are compiled, though,
599 they extract their arguments from the stack instead of the command line.
601 If compiled, the builtin words expect to find, at execution time, the
602 following parameters on the stack:
603 .D1 Ar addrN lenN ... addr2 len2 addr1 len1 N
606 are strings which will compose the command line that will be parsed
607 into the builtin's arguments.
608 Internally, these strings are concatenated in from 1 to N,
609 with a space put between each one.
611 If no arguments are passed, a 0
613 be passed, even if the builtin accepts no arguments.
615 While this behavior has benefits, it has its trade-offs.
616 If the execution token of a builtin is acquired (through
624 the builtin behavior will depend on the system state
632 \&! This is particularly annoying for programs that want or need to
634 In this case, the use of a proxy is recommended.
636 .Dl : (boot) boot \&;
639 is a Forth interpreter written in C, in the form of a forth
640 virtual machine library that can be called by C functions and vice
645 each line read interactively is then fed to
649 back to execute the builtin words.
656 The words available to
658 can be classified into four groups.
661 Forth standard words, extra
665 words, and the builtin commands;
666 the latter were already described.
669 Forth standard words are listed in the
672 The words falling in the two other groups are described in the
673 following subsections.
675 .Bl -tag -width wid-set-super
683 This is the STRING word set's
690 This is the STRING word set's
700 .Ss DRAGONFLY EXTRA WORDS
701 .Bl -tag -width XXXXXXXX
703 Evaluates the remainder of the input buffer, after having printed it first.
705 Evaluates the remainder of the input buffer under a
711 but without outputting a trailing space.
712 .It Ic fclose Pq Ar fd --
714 .It Ic fkey Pq Ar fd -- char
715 Reads a single character from a file.
716 .It Ic fload Pq Ar fd --
719 .It Ic fopen Pq Ar addr len mode Li -- Ar fd
721 Returns a file descriptor, or \-1 in case of failure.
724 parameter selects whether the file is to be opened for read access, write
727 .Dv O_RDONLY , O_WRONLY ,
732 indicating read only, write only, and read-write access, respectively.
735 .Pq Ar fd addr len -- len'
743 Returns the actual number of bytes read, or -1 in case of error or end of
745 .It Ic heap? Pq -- Ar cells
746 Return the space remaining in the dictionary heap, in cells.
747 This is not related to the heap used by dynamic memory allocation words.
748 .It Ic inb Pq Ar port -- char
749 Reads a byte from a port.
750 .It Ic key Pq -- Ar char
751 Reads a single character from the console.
752 .It Ic key? Pq -- Ar flag
755 if there is a character available to be read from the console.
760 .It Ic outb Pq Ar port char --
761 Writes a byte to a port.
762 .It Ic seconds Pq -- Ar u
763 Returns the number of seconds since midnight.
764 .It Ic tib> Pq -- Ar addr len
765 Returns the remainder of the input buffer as a string on the stack.
766 .It Ic trace! Pq Ar flag --
767 Activates or deactivates tracing.
771 .Ss DRAGONFLY DEFINED ENVIRONMENTAL QUERIES
775 if the architecture is IA32.
776 .It DragonFly_version
778 version at compile time.
783 .Ss SYSTEM DOCUMENTATION
785 .Bl -tag -width /boot/defaults/loader.conf -compact
789 .It Pa /boot/boot.4th
793 .It Pa /boot/boot.conf
795 bootstrapping script.
797 .It Pa /boot/defaults/loader.conf
798 .It Pa /boot/loader.conf
799 .It Pa /boot/loader.conf.local
801 configuration files, as described in
803 .It Pa /boot/loader.rc
805 bootstrapping script.
806 .It Pa /boot/loader.help
809 Contains the help messages.
812 Boot in single user mode:
816 Load kernel's user configuration file.
817 Notice that a kernel must be loaded before any other
819 command is attempted.
820 .Bd -literal -offset indent
822 load -t userconfig_script kernel.conf
825 Load the kernel, a splash screen, and then autoboot in five seconds.
826 .Bd -literal -offset indent
829 load -t splash_image_data chuckrulez.bmp
833 Set the disk unit of the root device to 2, and then boot.
834 This would be needed in a system with two IDE disks,
835 with the second IDE disk hardwired to ad2 instead of ad1.
836 .Bd -literal -offset indent
842 .Bl -tag -width /usr/share/examples/bootforth/X
844 Extra builtin-like words.
848 .It Pa /usr/share/examples/bootforth/
852 The following values are thrown by
854 .Bl -tag -width XXXXX -offset indent
856 Any type of error in the processing of a builtin.
867 Out of interpreting text.
869 Need more text to succeed -- will finish on next run.
885 For the purposes of ANS Forth compliance, loader is an
887 ANS Forth System with Environmental Restrictions, Providing
893 parse, pick, roll, refill, to, value, \e, false, true,
896 compile\&, , erase, nip, tuck
901 from the Core Extensions word set, Providing the Exception Extensions
902 word set, Providing the Locals Extensions word set, Providing the
903 Memory-Allocation Extensions word set, Providing
907 bye, forget, see, words,
914 from the Programming-Tools extension word set, Providing the
915 Search-Order extensions word set.
927 .An Michael Smith Aq msmith@FreeBSD.org .
931 .An John Sadler Aq john_sadler@alum.mit.edu .
937 words will read from the input buffer instead of the console.
938 The latter will be fixed, but the former will not.
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