1 .\" Copyright (c) 1999 Daniel C. Sobral
2 .\" All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
13 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
17 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 .Nd kernel bootstrapping final stage
38 kernel bootstrapping process.
39 On IA32 (i386) architectures, it is a
42 It is linked statically to
44 and usually located in the directory
47 It provides a scripting language that can be used to
48 automate tasks, do pre-configuration or assist in recovery
50 This scripting language is roughly divided in
52 The smaller one is a set of commands
53 designed for direct use by the casual user, called "builtin
54 commands" for historical reasons.
55 The main drive behind these commands is user-friendliness.
56 The bigger component is an
58 Forth compatible Forth interpreter based on FICL, by
61 During initialization,
63 will probe for a console and set the
65 variable, or set it to serial console
67 if the previous boot stage used that.
68 If multiple consoles are selected, they will be listed separated by spaces.
69 Then, devices are probed,
78 is initialized, the builtin words are added to its vocabulary, and
80 is processed if it exists.
81 No disk switching is possible while that file is being read.
93 is processed if available.
94 These files are processed through the
96 command, which reads all of them into memory before processing them,
97 making disk changes possible.
101 has not been tried, and if
105 (not case sensitive), then an
108 If the system gets past this point,
112 will engage interactive mode.
113 Please note that historically even when
117 user will be able to interrupt autoboot process by pressing some key
118 on the console while kernel and modules are being loaded.
120 cases such behaviour may be undesirable, to prevent it set
126 will engage interactive mode only if
132 builtin commands take parameters from the command line.
134 the only way to call them from a script is by using
137 If an error condition occurs, an exception will be generated,
138 which can be intercepted using
140 Forth exception handling
142 If not intercepted, an error message will be displayed and
143 the interpreter's state will be reset, emptying the stack and restoring
146 The builtin commands available are:
148 .Bl -tag -width Ds -compact
149 .It Ic autoboot Op Ar seconds Op Ar prompt
150 Proceeds to bootstrap the system after a number of seconds, if not
151 interrupted by the user.
152 Displays a countdown prompt
153 warning the user the system is about to be booted,
154 unless interrupted by a key press.
155 The kernel will be loaded first if necessary.
156 Defaults to 10 seconds.
159 Displays statistics about disk cache usage.
163 .It Ic boot Ar kernelname Op Cm ...
164 .It Ic boot Fl flag Cm ...
165 Immediately proceeds to bootstrap the system, loading the kernel
167 Any flags or arguments are passed to the kernel, but they
168 must precede the kernel name, if a kernel name is provided.
171 The behavior of this builtin is changed if
179 Displays text on the screen.
180 A new line will be printed unless
185 Displays memory usage statistics.
186 For debugging purposes only.
188 .It Ic help Op topic Op subtopic
189 Shows help messages read from
190 .Pa /boot/loader.help .
193 will list the topics available.
195 .It Ic include Ar file Op Ar
196 Process script files.
197 Each file, in turn, is completely read into memory,
198 and then each of its lines is passed to the command line interpreter.
199 If any error is returned by the interpreter, the include
200 command aborts immediately, without reading any other files, and
201 returns an error itself (see
208 Loads a kernel, kernel loadable module (kld), disk image,
209 or file of opaque contents tagged as being of the type
211 Kernel and modules can be either in a.out or ELF format.
212 Any arguments passed after the name of the file to be loaded
213 will be passed as arguments to that file.
216 type to make the kernel create a file-backed
219 This is useful for booting from a temporary rootfs.
220 Currently, argument passing does not work for the kernel.
228 encryption keyfile for the given provider name.
229 The key index can be specified via
231 or will default to zero.
237 Displays a listing of files in the directory
239 or the root directory if
244 is specified, file sizes will be shown too.
247 Lists all of the devices from which it may be possible to load modules,
248 as well as ZFS pools.
251 is specified, more details are printed, including ZFS pool information
252 in a format that resembles
257 Displays loaded modules.
260 is specified, more details are shown.
262 .It Ic lszfs Ar filesystem
263 A ZFS extended command that can be used to explore the ZFS filesystem
265 Lists the immediate children of the
267 The filesystem hierarchy is rooted at a filesystem with the same name
270 .It Ic more Ar file Op Ar
271 Display the files specified, with a pause at each
275 .It Ic pnpscan Op Fl v
276 Scans for Plug-and-Play devices.
277 This is not functional at present.
284 Reads a line of input from the terminal, storing it in
287 A timeout can be specified with
289 though it will be canceled at the first key pressed.
290 A prompt may also be displayed through the
295 Immediately reboots the system.
297 .It Ic set Ar variable
298 .It Ic set Ar variable Ns = Ns Ar value
299 Set loader's environment variables.
301 .It Ic show Op Va variable
302 Displays the specified variable's value, or all variables and their
308 Remove all modules from memory.
310 .It Ic unset Va variable
313 from the environment.
316 Lists available commands.
318 .Ss BUILTIN ENVIRONMENT VARIABLES
321 has actually two different kinds of
324 There are ANS Forth's
325 .Em environmental queries ,
326 and a separate space of environment variables used by builtins, which
327 are not directly available to Forth words.
328 It is the latter type that this section covers.
330 Environment variables can be set and unset through the
334 builtins, and can have their values interactively examined through the
338 Their values can also be accessed as described in
341 Notice that these environment variables are not inherited by any shell
342 after the system has been booted.
344 A few variables are set automatically by
346 Others can affect the behavior of either
348 or the kernel at boot.
349 Some options may require a value,
350 while others define behavior just by being set.
351 Both types of builtin variables are described below.
352 .Bl -tag -width bootfile
353 .It Va autoboot_delay
356 will wait before booting.
357 If this variable is not defined,
359 will default to 10 seconds.
365 will be automatically attempted after processing
366 .Pa /boot/loader.rc ,
369 will be processed normally, defaulting to 10 seconds delay.
373 no delay will be inserted, but user still will be able to interrupt
375 process and escape into the interactive mode by pressing some key
376 on the console while kernel and
377 modules are being loaded.
381 no delay will be inserted and
383 will engage interactive mode only if
385 has failed for some reason.
387 Instructs the kernel to prompt the user for the name of the root device
388 when the kernel is booted.
390 Instructs the kernel to try to mount the root file system from CD-ROM.
392 Instructs the kernel to start in the DDB debugger, rather than
393 proceeding to initialize when booted.
395 Instructs the kernel to mount the statically compiled-in root file system.
397 Selects gdb-remote mode for the kernel debugger by default.
398 .It Va boot_multicons
399 Enables multiple console support in the kernel early on boot.
400 In a running system, console configuration can be manipulated
405 All kernel console output is suppressed when console is muted.
406 In a running system, the state of console muting can be manipulated by the
410 During the device probe, pause after each line is printed.
412 Force the use of a serial console even when an internal console
415 Prevents the kernel from initiating a multi-user startup; instead,
416 a single-user mode will be entered when the kernel has finished
419 Setting this variable causes extra debugging information to be printed
420 by the kernel during the boot phase.
422 List of semicolon-separated search path for bootable kernels.
425 .It Va comconsole_speed
426 Defines the speed of the serial console (i386 and amd64 only).
427 If the previous boot stage indicated that a serial console is in use
428 then this variable is initialized to the current speed of the console
430 Otherwise it is set to 9600 unless this was overridden using the
431 .Va BOOT_COMCONSOLE_SPEED
437 variable take effect immediately.
438 .It Va comconsole_port
439 Defines the base i/o port used to access console UART
440 (i386 and amd64 only).
441 If the variable is not set, its assumed value is 0x3F8, which
442 corresponds to PC port COM1, unless overridden by
443 .Va BOOT_COMCONSOLE_PORT
444 variable during the compilation of
448 variable automatically set
450 environment variable to provide a hint to kernel for location of the console.
451 Loader console is changed immediately after variable
454 .It Va comconsole_pcidev
455 Defines the location of a PCI device of the 'simple communication'
456 class to be used as the serial console UART (i386 and amd64 only).
457 The syntax of the variable is
458 .Li 'bus:device:function[:bar]' ,
459 where all members must be numeric, with possible
461 prefix to indicate a hexadecimal value.
464 member is optional and assumed to be 0x10 if omitted.
465 The bar must decode i/o space.
467 .Va comconsole_pcidev
468 automatically sets the variable
470 to the base of the selected bar, and hint
471 .Va hw.uart.console .
472 Loader console is changed immediately after variable
473 .Va comconsole_pcidev
476 Defines the current console or consoles.
477 Multiple consoles may be specified.
478 In that case, the first listed console will become the default console for
479 userland output (e.g.\& from
482 Selects the default device.
483 Syntax for devices is odd.
485 Sets the device for kernel dumps.
486 This can be used to ensure that a device is configured before the corresponding
490 has been processed, allowing kernel panics that happen during the early stages
491 of boot to be captured.
499 Sets the list of binaries which the kernel will try to run as the initial
501 The first matching binary is used.
503 .Dq Li /sbin/init:/sbin/oinit:/sbin/init.bak:\:/rescue/init .
513 if the Forth's current state is interpreting.
515 Define the number of lines on the screen, to be used by the pager.
517 Sets the list of directories which will be searched for modules
518 named in a load command or implicitly required by a dependency.
519 The default value for this variable is
520 .Dq Li /boot/kernel;/boot/modules .
522 Sets the number of IDE disks as a workaround for some problems in
523 finding the root disk at boot.
524 This has been deprecated in favor of
531 .Dq Li "${interpret}" .
534 is unset, the default prompt is
536 .It Va root_disk_unit
537 If the code which detects the disk unit number for the root disk is
538 confused, e.g.\& by a mix of SCSI and IDE disks, or IDE disks with
539 gaps in the sequence (e.g.\& no primary slave), the unit number can
540 be forced by setting this variable.
542 By default the value of
544 is used to set the root file system
545 when the kernel is booted.
546 This can be overridden by setting
551 Other variables are used to override kernel tunable parameters.
552 The following tunables are available:
554 .It Va efi.rt.disabled
555 Disable UEFI runtime services in the kernel, if applicable.
556 Runtime services are only available and used if the kernel is booted in a UEFI
559 Limit the amount of physical memory the system will use.
560 By default the size is in bytes, but the
561 .Cm k , K , m , M , g
565 are also accepted and indicate kilobytes, megabytes and gigabytes
567 An invalid suffix will result in the variable being ignored by the
569 .It Va hw.pci.host_start_mem , hw.acpi.host_start_mem
570 When not otherwise constrained, this limits the memory start
572 The default is 0x80000000 and should be set to at least size of the
573 memory and not conflict with other resources.
574 Typically, only systems without PCI bridges need to set this variable
575 since PCI bridges typically constrain the memory starting address
576 (and the variable is only used when bridges do not constrain this
578 .It Va hw.pci.enable_io_modes
579 Enable PCI resources which are left off by some BIOSes or are not
580 enabled correctly by the device driver.
581 Tunable value set to ON (1) by default, but this may cause problems
582 with some peripherals.
584 Set the size of a number of statically allocated system tables; see
586 for a description of how to select an appropriate value for this
588 When set, this tunable replaces the value declared in the kernel
589 compile-time configuration file.
590 .It Va kern.ipc.nmbclusters
591 Set the number of mbuf clusters to be allocated.
592 The value cannot be set below the default
593 determined when the kernel was compiled.
594 .It Va kern.ipc.nsfbufs
597 buffers to be allocated.
600 Not all architectures use such buffers; see
603 .It Va kern.maxswzone
604 Limits the amount of KVM to be used to hold swap
605 metadata, which directly governs the
606 maximum amount of swap the system can support,
607 at the rate of approximately 200 MB of swap space
608 per 1 MB of metadata.
609 This value is specified in bytes of KVA space.
610 If no value is provided, the system allocates
611 enough memory to handle an amount of swap
612 that corresponds to eight times the amount of
613 physical memory present in the system.
615 Note that swap metadata can be fragmented,
616 which means that the system can run out of
617 space before it reaches the theoretical limit.
618 Therefore, care should be taken to not configure
619 more swap than approximately half of the
622 Running out of space for swap metadata can leave
623 the system in an unrecoverable state.
624 Therefore, you should only change
625 this parameter if you need to greatly extend the
626 KVM reservation for other resources such as the
628 .Va kern.ipc.nmbclusters .
629 Modifies kernel option
630 .Dv VM_SWZONE_SIZE_MAX .
631 .It Va kern.maxbcache
632 Limits the amount of KVM reserved for use by the
633 buffer cache, specified in bytes.
634 The default maximum is 200MB on i386,
635 and 400MB on amd64 and sparc64.
636 This parameter is used to
637 prevent the buffer cache from eating too much
638 KVM in large-memory machine configurations.
639 Only mess around with this parameter if you need to
640 greatly extend the KVM reservation for other resources
641 such as the swap zone or
642 .Va kern.ipc.nmbclusters .
644 the NBUF parameter will override this limit.
646 .Dv VM_BCACHE_SIZE_MAX .
647 .It Va kern.msgbufsize
648 Sets the size of the kernel message buffer.
649 The default limit of 64KB is usually sufficient unless
650 large amounts of trace data need to be collected
651 between opportunities to examine the buffer or
653 Overrides kernel option
655 .It Va machdep.disable_mtrrs
656 Disable the use of i686 MTRRs (x86 only).
657 .It Va net.inet.tcp.tcbhashsize
658 Overrides the compile-time set value of
660 or the preset default of 512.
661 Must be a power of 2.
662 .It Va twiddle_divisor
663 Throttles the output of the
665 I/O progress indicator displayed while loading the kernel and modules.
666 This is useful on slow serial consoles where the time spent waiting for
667 these characters to be written can add up to many seconds.
668 The default is 1 (full speed); a value of 2 spins half as fast, and so on.
670 Sets the size of kernel memory (bytes).
671 This overrides the value determined when the kernel was compiled.
674 .It Va vm.kmem_size_min
675 .It Va vm.kmem_size_max
676 Sets the minimum and maximum (respectively) amount of kernel memory
677 that will be automatically allocated by the kernel.
678 These override the values determined when the kernel was compiled.
682 .Dv VM_KMEM_SIZE_MAX .
686 supports the following format for specifying ZFS filesystems which
689 refers to a device specification:
691 .Ar zfs:pool/filesystem:
695 is a ZFS filesystem name as described in
700 does not have an entry for the root filesystem and
701 .Va vfs.root.mountfrom
704 refers to a ZFS filesystem, then
706 will instruct kernel to use that filesystem as the root filesystem.
708 When a builtin command is executed, the rest of the line is taken
709 by it as arguments, and it is processed by a special parser which
710 is not used for regular Forth commands.
712 This special parser applies the following rules to the parsed text:
715 All backslash characters are preprocessed.
718 \eb , \ef , \er , \en and \et are processed as in C.
720 \es is converted to a space.
727 Useful for things like
730 \e0xN and \e0xNN are replaced by the hex N or NN.
732 \eNNN is replaced by the octal NNN
736 \e" , \e' and \e$ will escape these characters, preventing them from
737 receiving special treatment in Step 2, described below.
739 \e\e will be replaced with a single \e .
741 In any other occurrence, backslash will just be removed.
744 Every string between non-escaped quotes or double-quotes will be treated
745 as a single word for the purposes of the remaining steps.
751 with the value of the environment variable
754 Space-delimited arguments are passed to the called builtin command.
755 Spaces can also be escaped through the use of \e\e .
758 An exception to this parsing rule exists, and is described in
759 .Sx BUILTINS AND FORTH .
760 .Ss BUILTINS AND FORTH
761 All builtin words are state-smart, immediate words.
762 If interpreted, they behave exactly as described previously.
763 If they are compiled, though,
764 they extract their arguments from the stack instead of the command line.
766 If compiled, the builtin words expect to find, at execution time, the
767 following parameters on the stack:
768 .D1 Ar addrN lenN ... addr2 len2 addr1 len1 N
771 are strings which will compose the command line that will be parsed
772 into the builtin's arguments.
773 Internally, these strings are concatenated in from 1 to N,
774 with a space put between each one.
776 If no arguments are passed, a 0
778 be passed, even if the builtin accepts no arguments.
780 While this behavior has benefits, it has its trade-offs.
781 If the execution token of a builtin is acquired (through
789 the builtin behavior will depend on the system state
797 This is particularly annoying for programs that want or need to
799 In this case, the use of a proxy is recommended.
804 is a Forth interpreter written in C, in the form of a forth
805 virtual machine library that can be called by C functions and vice
810 each line read interactively is then fed to
814 back to execute the builtin words.
821 The words available to
823 can be classified into four groups.
826 Forth standard words, extra
830 words, and the builtin commands;
831 the latter were already described.
834 Forth standard words are listed in the
837 The words falling in the two other groups are described in the
838 following subsections.
840 .Bl -tag -width wid-set-super
848 This is the STRING word set's
855 This is the STRING word set's
865 .Ss FREEBSD EXTRA WORDS
866 .Bl -tag -width XXXXXXXX
868 Evaluates the remainder of the input buffer, after having printed it first.
870 Evaluates the remainder of the input buffer under a
876 but without outputting a trailing space.
877 .It Ic fclose Pq Ar fd --
879 .It Ic fkey Pq Ar fd -- char
880 Reads a single character from a file.
881 .It Ic fload Pq Ar fd --
884 .It Ic fopen Pq Ar addr len mode Li -- Ar fd
886 Returns a file descriptor, or \-1 in case of failure.
889 parameter selects whether the file is to be opened for read access, write
892 .Dv O_RDONLY , O_WRONLY ,
896 .Pa /boot/support.4th ,
897 indicating read only, write only, and read-write access, respectively.
900 .Pq Ar fd addr len -- len'
908 Returns the actual number of bytes read, or -1 in case of error or end of
910 .It Ic heap? Pq -- Ar cells
911 Return the space remaining in the dictionary heap, in cells.
912 This is not related to the heap used by dynamic memory allocation words.
913 .It Ic inb Pq Ar port -- char
914 Reads a byte from a port.
915 .It Ic key Pq -- Ar char
916 Reads a single character from the console.
917 .It Ic key? Pq -- Ar flag
920 if there is a character available to be read from the console.
925 .It Ic outb Pq Ar port char --
926 Writes a byte to a port.
927 .It Ic seconds Pq -- Ar u
928 Returns the number of seconds since midnight.
929 .It Ic tib> Pq -- Ar addr len
930 Returns the remainder of the input buffer as a string on the stack.
931 .It Ic trace! Pq Ar flag --
932 Activates or deactivates tracing.
936 .Ss FREEBSD DEFINED ENVIRONMENTAL QUERIES
940 if the architecture is IA32.
943 version at compile time.
951 command line provides several ways of compromising system security,
952 including, but not limited to:
956 Booting from removable storage, by setting the
962 Executing binary of choice, by setting the
968 Overriding ACPI DSDT to inject arbitrary code into the ACPI subsystem
971 One can prevent unauthorized access
974 command line by setting the
982 In order for this to be effective, one should also configure the firmware
983 (BIOS or UEFI) to prevent booting from unauthorized devices.
985 .Bl -tag -width /usr/share/examples/bootforth/ -compact
989 .It Pa /boot/boot.4th
993 .It Pa /boot/defaults/loader.conf
994 .It Pa /boot/loader.4th
995 Extra builtin-like words.
996 .It Pa /boot/loader.conf
997 .It Pa /boot/loader.conf.local
999 configuration files, as described in
1001 .It Pa /boot/loader.rc
1003 bootstrapping script.
1004 .It Pa /boot/loader.help
1007 Contains the help messages.
1008 .It Pa /boot/support.4th
1011 .It Pa /usr/share/examples/bootforth/
1015 Boot in single user mode:
1019 Load the kernel, a splash screen, and then autoboot in five seconds.
1020 Notice that a kernel must be loaded before any other
1022 command is attempted.
1023 .Bd -literal -offset indent
1026 load -t splash_image_data /boot/chuckrulez.bmp
1030 Set the disk unit of the root device to 2, and then boot.
1031 This would be needed in a system with two IDE disks,
1032 with the second IDE disk hardwired to ada2 instead of ada1.
1033 .Bd -literal -offset indent
1034 set root_disk_unit=2
1035 boot /boot/kernel/kernel
1038 Set the default device used for loading a kernel from a ZFS filesystem:
1039 .Bd -literal -offset indent
1040 set currdev=zfs:tank/ROOT/knowngood:
1044 The following values are thrown by
1046 .Bl -tag -width XXXXX -offset indent
1048 Any type of error in the processing of a builtin.
1059 Out of interpreting text.
1061 Need more text to succeed -- will finish on next run.
1075 For the purposes of ANS Forth compliance, loader is an
1077 ANS Forth System with Environmental Restrictions, Providing
1083 parse, pick, roll, refill, to, value, \e, false, true,
1086 compile\&, , erase, nip, tuck
1091 from the Core Extensions word set, Providing the Exception Extensions
1092 word set, Providing the Locals Extensions word set, Providing the
1093 Memory-Allocation Extensions word set, Providing
1097 bye, forget, see, words,
1104 from the Programming-Tools extension word set, Providing the
1105 Search-Order extensions word set.
1117 .An Michael Smith Aq msmith@FreeBSD.org .
1121 .An John Sadler Aq john_sadler@alum.mit.edu .
1127 words will read from the input buffer instead of the console.
1128 The latter will be fixed, but the former will not.
projects / FreeBSD / FreeBSD.git / blob