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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, and, failing that,
95 is read for historical reasons.
96 These files are processed through the
98 command, which reads all of them into memory before processing them,
99 making disk changes possible.
103 has not been tried, and if
107 (not case sensitive), then an
110 If the system gets past this point,
114 will engage interactive mode.
115 Please note that historically even when
119 user will be able to interrupt autoboot process by pressing some key
120 on the console while kernel and modules are being loaded.
122 cases such behaviour may be undesirable, to prevent it set
128 will engage interactive mode only if
134 builtin commands take parameters from the command line.
136 the only way to call them from a script is by using
139 If an error condition occurs, an exception will be generated,
140 which can be intercepted using
142 Forth exception handling
144 If not intercepted, an error message will be displayed and
145 the interpreter's state will be reset, emptying the stack and restoring
148 The builtin commands available are:
150 .Bl -tag -width Ds -compact
151 .It Ic autoboot Op Ar seconds Op Ar prompt
152 Proceeds to bootstrap the system after a number of seconds, if not
153 interrupted by the user.
154 Displays a countdown prompt
155 warning the user the system is about to be booted,
156 unless interrupted by a key press.
157 The kernel will be loaded first if necessary.
158 Defaults to 10 seconds.
161 Displays statistics about disk cache usage.
165 .It Ic boot Ar kernelname Op Cm ...
166 .It Ic boot Fl flag Cm ...
167 Immediately proceeds to bootstrap the system, loading the kernel
169 Any flags or arguments are passed to the kernel, but they
170 must precede the kernel name, if a kernel name is provided.
173 The behavior of this builtin is changed if
181 Displays text on the screen.
182 A new line will be printed unless
187 Displays memory usage statistics.
188 For debugging purposes only.
190 .It Ic help Op topic Op subtopic
191 Shows help messages read from
192 .Pa /boot/loader.help .
195 will list the topics available.
197 .It Ic include Ar file Op Ar
198 Process script files.
199 Each file, in turn, is completely read into memory,
200 and then each of its lines is passed to the command line interpreter.
201 If any error is returned by the interpreter, the include
202 command aborts immediately, without reading any other files, and
203 returns an error itself (see
210 Loads a kernel, kernel loadable module (kld), or file of opaque
211 contents tagged as being of the type
213 Kernel and modules can be either in a.out or ELF format.
214 Any arguments passed after the name of the file to be loaded
215 will be passed as arguments to that file.
216 Currently, argument passing does not work for the kernel.
224 encryption keyfile for the given provider name.
225 The key index can be specified via
227 or will default to zero.
233 Displays a listing of files in the directory
235 or the root directory if
240 is specified, file sizes will be shown too.
243 Lists all of the devices from which it may be possible to load modules.
246 is specified, more details are printed.
249 Displays loaded modules.
252 is specified, more details are shown.
254 .It Ic more Ar file Op Ar
255 Display the files specified, with a pause at each
259 .It Ic pnpscan Op Fl v
260 Scans for Plug-and-Play devices.
261 This is not functional at present.
268 Reads a line of input from the terminal, storing it in
271 A timeout can be specified with
273 though it will be canceled at the first key pressed.
274 A prompt may also be displayed through the
279 Immediately reboots the system.
281 .It Ic set Ar variable
282 .It Ic set Ar variable Ns = Ns Ar value
283 Set loader's environment variables.
285 .It Ic show Op Va variable
286 Displays the specified variable's value, or all variables and their
292 Remove all modules from memory.
294 .It Ic unset Va variable
297 from the environment.
300 Lists available commands.
302 .Ss BUILTIN ENVIRONMENT VARIABLES
305 has actually two different kinds of
308 There are ANS Forth's
309 .Em environmental queries ,
310 and a separate space of environment variables used by builtins, which
311 are not directly available to Forth words.
312 It is the latter type that this section covers.
314 Environment variables can be set and unset through the
318 builtins, and can have their values interactively examined through the
322 Their values can also be accessed as described in
325 Notice that these environment variables are not inherited by any shell
326 after the system has been booted.
328 A few variables are set automatically by
330 Others can affect the behavior of either
332 or the kernel at boot.
333 Some options may require a value,
334 while others define behavior just by being set.
335 Both types of builtin variables are described below.
336 .Bl -tag -width bootfile
338 Unset this to disable automatic loading of the ACPI module.
340 .Va hint.acpi.0.disabled
343 .It Va autoboot_delay
346 will wait before booting.
347 If this variable is not defined,
349 will default to 10 seconds.
355 will be automatically attempted after processing
356 .Pa /boot/loader.rc ,
359 will be processed normally, defaulting to 10 seconds delay.
363 no delay will be inserted, but user still will be able to interrupt
365 process and escape into the interactive mode by pressing some key
366 on the console while kernel and
367 modules are being loaded.
371 no delay will be inserted and
373 will engage interactive mode only if
375 has failed for some reason.
377 Instructs the kernel to prompt the user for the name of the root device
378 when the kernel is booted.
380 Instructs the kernel to try to mount the root file system from CD-ROM.
382 Instructs the kernel to start in the DDB debugger, rather than
383 proceeding to initialize when booted.
385 Instructs the kernel to mount the statically compiled-in root file system.
387 Selects gdb-remote mode for the kernel debugger by default.
388 .It Va boot_multicons
389 Enables multiple console support in the kernel early on boot.
390 In a running system, console configuration can be manipulated
395 All console output is suppressed when console is muted.
396 In a running system, the state of console muting can be manipulated by the
400 During the device probe, pause after each line is printed.
402 Force the use of a serial console even when an internal console
405 Prevents the kernel from initiating a multi-user startup; instead,
406 a single-user mode will be entered when the kernel has finished
409 Setting this variable causes extra debugging information to be printed
410 by the kernel during the boot phase.
412 List of semicolon-separated search path for bootable kernels.
415 .It Va comconsole_speed
416 Defines the speed of the serial console (i386 and amd64 only).
417 If the previous boot stage indicated that a serial console is in use
418 then this variable is initialized to the current speed of the console
420 Otherwise it is set to 9600 unless this was overridden using the
421 .Va BOOT_COMCONSOLE_SPEED
427 variable take effect immediately.
429 Defines the current console or consoles.
430 Multiple consoles may be specified.
431 In that case, the first listed console will become the default console for
432 userland output (e.g.\& from
435 Selects the default device.
436 Syntax for devices is odd.
438 If set to a valid directory in the root file system, it causes
442 operation on that directory, making it the new root directory.
443 That happens before entering single-user mode or multi-user
444 mode (but after executing the
448 Sets the list of binaries which the kernel will try to run as the initial
450 The first matching binary is used.
452 .Dq Li /sbin/init:/sbin/oinit:/sbin/init.bak:\:/rescue/init:/stand/sysinstall .
454 If set to a valid file name in the root file system,
457 to run that script as the very first action,
458 before doing anything else.
459 Signal handling and exit code interpretation is similar to
463 In particular, single-user operation is enforced
464 if the script terminates with a non-zero exit code,
465 or if a SIGTERM is delivered to the
469 Defines the shell binary to be used for executing the various shell scripts.
472 It is used for running the
474 if set, as well as for the
479 The value of the corresponding
481 variable is evaluated every time
483 calls a shell script, so it can be changed later on using the
486 In particular, if a non-default shell is used for running an
488 it might be desirable to have that script reset the value of
490 back to the default, so that the
492 script is executed with the standard shell
497 if the Forth's current state is interpreting.
499 Define the number of lines on the screen, to be used by the pager.
501 Sets the list of directories which will be searched for modules
502 named in a load command or implicitly required by a dependency.
503 The default value for this variable is
504 .Dq Li /boot/kernel;/boot/modules .
506 Sets the number of IDE disks as a workaround for some problems in
507 finding the root disk at boot.
508 This has been deprecated in favor of
515 .Dq Li "${interpret}" .
518 is unset, the default prompt is
520 .It Va root_disk_unit
521 If the code which detects the disk unit number for the root disk is
522 confused, e.g.\& by a mix of SCSI and IDE disks, or IDE disks with
523 gaps in the sequence (e.g.\& no primary slave), the unit number can
524 be forced by setting this variable.
526 By default the value of
528 is used to set the root file system
529 when the kernel is booted.
530 This can be overridden by setting
535 Other variables are used to override kernel tunable parameters.
536 The following tunables are available:
539 Limit the amount of physical memory the system will use.
540 By default the size is in bytes, but the
541 .Cm k , K , m , M , g
545 are also accepted and indicate kilobytes, megabytes and gigabytes
547 An invalid suffix will result in the variable being ignored by the
549 .It Va hw.pci.host_start_mem , hw.acpi.host_start_mem
550 When not otherwise constrained, this limits the memory start
552 The default is 0x80000000 and should be set to at least size of the
553 memory and not conflict with other resources.
554 Typically, only systems without PCI bridges need to set this variable
555 since PCI bridges typically constrain the memory starting address
556 (and the variable is only used when bridges do not constrain this
558 .It Va hw.pci.enable_io_modes
559 Enable PCI resources which are left off by some BIOSes or are not
560 enabled correctly by the device driver.
561 Tunable value set to ON (1) by default, but this may cause problems
562 with some peripherals.
564 Set the size of a number of statically allocated system tables; see
566 for a description of how to select an appropriate value for this
568 When set, this tunable replaces the value declared in the kernel
569 compile-time configuration file.
570 .It Va kern.ipc.nmbclusters
571 Set the number of mbuf clusters to be allocated.
572 The value cannot be set below the default
573 determined when the kernel was compiled.
574 .It Va kern.ipc.nsfbufs
577 buffers to be allocated.
580 Not all architectures use such buffers; see
583 .It Va kern.maxswzone
584 Limits the amount of KVM to be used to hold swap
585 meta information, which directly governs the
586 maximum amount of swap the system can support.
587 This value is specified in bytes of KVA space
588 and defaults to 32MBytes on i386 and amd64.
590 to not reduce this value such that the actual
591 amount of configured swap exceeds 1/2 the
592 kernel-supported swap.
593 The default of 32MB allows
594 the kernel to support a maximum of ~7GB of swap.
596 this parameter if you need to greatly extend the
597 KVM reservation for other resources such as the
599 .Va kern.ipc.nmbclusters .
600 Modifies kernel option
601 .Dv VM_SWZONE_SIZE_MAX .
602 .It Va kern.maxbcache
603 Limits the amount of KVM reserved for use by the
604 buffer cache, specified in bytes.
605 The default maximum is 200MB on i386,
606 and 400MB on amd64, sparc64, and sun4v.
607 This parameter is used to
608 prevent the buffer cache from eating too much
609 KVM in large-memory machine configurations.
610 Only mess around with this parameter if you need to
611 greatly extend the KVM reservation for other resources
612 such as the swap zone or
613 .Va kern.ipc.nmbclusters .
615 the NBUF parameter will override this limit.
617 .Dv VM_BCACHE_SIZE_MAX .
618 .It Va machdep.disable_mtrrs
619 Disable the use of i686 MTRRs (x86 only).
620 .It Va net.inet.tcp.tcbhashsize
621 Overrides the compile-time set value of
623 or the preset default of 512.
624 Must be a power of 2.
626 Sets the size of kernel memory (bytes).
627 This overrides the value determined when the kernel was compiled.
630 .It Va vm.kmem_size_min
631 .It Va vm.kmem_size_max
632 Sets the minimum and maximum (respectively) amount of kernel memory
633 that will be automatically allocated by the kernel.
634 These override the values determined when the kernel was compiled.
638 .Dv VM_KMEM_SIZE_MAX .
641 When a builtin command is executed, the rest of the line is taken
642 by it as arguments, and it is processed by a special parser which
643 is not used for regular Forth commands.
645 This special parser applies the following rules to the parsed text:
649 All backslash characters are preprocessed.
652 \eb , \ef , \er , \en and \et are processed as in C.
654 \es is converted to a space.
661 Useful for things like
664 \e0xN and \e0xNN are replaced by the hex N or NN.
666 \eNNN is replaced by the octal NNN
670 \e" , \e' and \e$ will escape these characters, preventing them from
671 receiving special treatment in Step 2, described below.
673 \e\e will be replaced with a single \e .
675 In any other occurrence, backslash will just be removed.
678 Every string between non-escaped quotes or double-quotes will be treated
679 as a single word for the purposes of the remaining steps.
685 with the value of the environment variable
688 Space-delimited arguments are passed to the called builtin command.
689 Spaces can also be escaped through the use of \e\e .
692 An exception to this parsing rule exists, and is described in
693 .Sx BUILTINS AND FORTH .
694 .Ss BUILTINS AND FORTH
695 All builtin words are state-smart, immediate words.
696 If interpreted, they behave exactly as described previously.
697 If they are compiled, though,
698 they extract their arguments from the stack instead of the command line.
700 If compiled, the builtin words expect to find, at execution time, the
701 following parameters on the stack:
702 .D1 Ar addrN lenN ... addr2 len2 addr1 len1 N
705 are strings which will compose the command line that will be parsed
706 into the builtin's arguments.
707 Internally, these strings are concatenated in from 1 to N,
708 with a space put between each one.
710 If no arguments are passed, a 0
712 be passed, even if the builtin accepts no arguments.
714 While this behavior has benefits, it has its trade-offs.
715 If the execution token of a builtin is acquired (through
723 the builtin behavior will depend on the system state
731 This is particularly annoying for programs that want or need to
733 In this case, the use of a proxy is recommended.
738 is a Forth interpreter written in C, in the form of a forth
739 virtual machine library that can be called by C functions and vice
744 each line read interactively is then fed to
748 back to execute the builtin words.
755 The words available to
757 can be classified into four groups.
760 Forth standard words, extra
764 words, and the builtin commands;
765 the latter were already described.
768 Forth standard words are listed in the
771 The words falling in the two other groups are described in the
772 following subsections.
774 .Bl -tag -width wid-set-super
782 This is the STRING word set's
789 This is the STRING word set's
799 .Ss FREEBSD EXTRA WORDS
800 .Bl -tag -width XXXXXXXX
802 Evaluates the remainder of the input buffer, after having printed it first.
804 Evaluates the remainder of the input buffer under a
810 but without outputting a trailing space.
811 .It Ic fclose Pq Ar fd --
813 .It Ic fkey Pq Ar fd -- char
814 Reads a single character from a file.
815 .It Ic fload Pq Ar fd --
818 .It Ic fopen Pq Ar addr len mode Li -- Ar fd
820 Returns a file descriptor, or \-1 in case of failure.
823 parameter selects whether the file is to be opened for read access, write
826 .Dv O_RDONLY , O_WRONLY ,
830 .Pa /boot/support.4th ,
831 indicating read only, write only, and read-write access, respectively.
834 .Pq Ar fd addr len -- len'
842 Returns the actual number of bytes read, or -1 in case of error or end of
844 .It Ic heap? Pq -- Ar cells
845 Return the space remaining in the dictionary heap, in cells.
846 This is not related to the heap used by dynamic memory allocation words.
847 .It Ic inb Pq Ar port -- char
848 Reads a byte from a port.
849 .It Ic key Pq -- Ar char
850 Reads a single character from the console.
851 .It Ic key? Pq -- Ar flag
854 if there is a character available to be read from the console.
859 .It Ic outb Pq Ar port char --
860 Writes a byte to a port.
861 .It Ic seconds Pq -- Ar u
862 Returns the number of seconds since midnight.
863 .It Ic tib> Pq -- Ar addr len
864 Returns the remainder of the input buffer as a string on the stack.
865 .It Ic trace! Pq Ar flag --
866 Activates or deactivates tracing.
870 .Ss FREEBSD DEFINED ENVIRONMENTAL QUERIES
874 if the architecture is IA32.
877 version at compile time.
882 .Ss SYSTEM DOCUMENTATION
884 .Bl -tag -width /boot/defaults/loader.conf -compact
888 .It Pa /boot/boot.4th
892 .It Pa /boot/boot.conf
894 bootstrapping script.
896 .It Pa /boot/defaults/loader.conf
897 .It Pa /boot/loader.conf
898 .It Pa /boot/loader.conf.local
900 configuration files, as described in
902 .It Pa /boot/loader.rc
904 bootstrapping script.
905 .It Pa /boot/loader.help
908 Contains the help messages.
911 Boot in single user mode:
915 Load the kernel, a splash screen, and then autoboot in five seconds.
916 Notice that a kernel must be loaded before any other
918 command is attempted.
919 .Bd -literal -offset indent
922 load -t splash_image_data /boot/chuckrulez.bmp
926 Set the disk unit of the root device to 2, and then boot.
927 This would be needed in a system with two IDE disks,
928 with the second IDE disk hardwired to wd2 instead of wd1.
929 .Bd -literal -offset indent
935 .Bl -tag -width /usr/share/examples/bootforth/X
936 .It Pa /boot/loader.4th
937 Extra builtin-like words.
938 .It Pa /boot/support.4th
941 .It Pa /usr/share/examples/bootforth/
945 The following values are thrown by
947 .Bl -tag -width XXXXX -offset indent
949 Any type of error in the processing of a builtin.
960 Out of interpreting text.
962 Need more text to succeed -- will finish on next run.
976 For the purposes of ANS Forth compliance, loader is an
978 ANS Forth System with Environmental Restrictions, Providing
984 parse, pick, roll, refill, to, value, \e, false, true,
987 compile\&, , erase, nip, tuck
992 from the Core Extensions word set, Providing the Exception Extensions
993 word set, Providing the Locals Extensions word set, Providing the
994 Memory-Allocation Extensions word set, Providing
998 bye, forget, see, words,
1005 from the Programming-Tools extension word set, Providing the
1006 Search-Order extensions word set.
1018 .An Michael Smith Aq msmith@FreeBSD.org .
1022 .An John Sadler Aq john_sadler@alum.mit.edu .
1028 words will read from the input buffer instead of the console.
1029 The latter will be fixed, but the former will not.
projects / FreeBSD / releng / 8.1.git / blob