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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
337 .It Va autoboot_delay
340 will wait before booting.
341 If this variable is not defined,
343 will default to 10 seconds.
349 will be automatically attempted after processing
350 .Pa /boot/loader.rc ,
353 will be processed normally, defaulting to 10 seconds delay.
357 no delay will be inserted, but user still will be able to interrupt
359 process and escape into the interactive mode by pressing some key
360 on the console while kernel and
361 modules are being loaded.
365 no delay will be inserted and
367 will engage interactive mode only if
369 has failed for some reason.
371 Instructs the kernel to prompt the user for the name of the root device
372 when the kernel is booted.
374 Instructs the kernel to try to mount the root file system from CD-ROM.
376 Instructs the kernel to start in the DDB debugger, rather than
377 proceeding to initialize when booted.
379 Instructs the kernel to mount the statically compiled-in root file system.
381 Selects gdb-remote mode for the kernel debugger by default.
382 .It Va boot_multicons
383 Enables multiple console support in the kernel early on boot.
384 In a running system, console configuration can be manipulated
389 All console output is suppressed when console is muted.
390 In a running system, the state of console muting can be manipulated by the
394 During the device probe, pause after each line is printed.
396 Force the use of a serial console even when an internal console
399 Prevents the kernel from initiating a multi-user startup; instead,
400 a single-user mode will be entered when the kernel has finished
403 Setting this variable causes extra debugging information to be printed
404 by the kernel during the boot phase.
406 List of semicolon-separated search path for bootable kernels.
409 .It Va comconsole_speed
410 Defines the speed of the serial console (i386 and amd64 only).
411 If the previous boot stage indicated that a serial console is in use
412 then this variable is initialized to the current speed of the console
414 Otherwise it is set to 9600 unless this was overridden using the
415 .Va BOOT_COMCONSOLE_SPEED
421 variable take effect immediately.
423 Defines the current console or consoles.
424 Multiple consoles may be specified.
425 In that case, the first listed console will become the default console for
426 userland output (e.g.\& from
429 Selects the default device.
430 Syntax for devices is odd.
432 If set to a valid directory in the root file system, it causes
436 operation on that directory, making it the new root directory.
437 That happens before entering single-user mode or multi-user
438 mode (but after executing the
442 Sets the list of binaries which the kernel will try to run as the initial
444 The first matching binary is used.
446 .Dq Li /sbin/init:/sbin/oinit:/sbin/init.bak:\:/rescue/init:/stand/sysinstall .
448 If set to a valid file name in the root file system,
451 to run that script as the very first action,
452 before doing anything else.
453 Signal handling and exit code interpretation is similar to
457 In particular, single-user operation is enforced
458 if the script terminates with a non-zero exit code,
459 or if a SIGTERM is delivered to the
463 Defines the shell binary to be used for executing the various shell scripts.
466 It is used for running the
468 if set, as well as for the
473 The value of the corresponding
475 variable is evaluated every time
477 calls a shell script, so it can be changed later on using the
480 In particular, if a non-default shell is used for running an
482 it might be desirable to have that script reset the value of
484 back to the default, so that the
486 script is executed with the standard shell
491 if the Forth's current state is interpreting.
493 Define the number of lines on the screen, to be used by the pager.
495 Sets the list of directories which will be searched for modules
496 named in a load command or implicitly required by a dependency.
497 The default value for this variable is
498 .Dq Li /boot/kernel;/boot/modules .
500 Sets the number of IDE disks as a workaround for some problems in
501 finding the root disk at boot.
502 This has been deprecated in favor of
509 .Dq Li "${interpret}" .
512 is unset, the default prompt is
514 .It Va root_disk_unit
515 If the code which detects the disk unit number for the root disk is
516 confused, e.g.\& by a mix of SCSI and IDE disks, or IDE disks with
517 gaps in the sequence (e.g.\& no primary slave), the unit number can
518 be forced by setting this variable.
520 By default the value of
522 is used to set the root file system
523 when the kernel is booted.
524 This can be overridden by setting
529 Other variables are used to override kernel tunable parameters.
530 The following tunables are available:
533 Limit the amount of physical memory the system will use.
534 By default the size is in bytes, but the
535 .Cm k , K , m , M , g
539 are also accepted and indicate kilobytes, megabytes and gigabytes
541 An invalid suffix will result in the variable being ignored by the
543 .It Va hw.pci.host_start_mem , hw.acpi.host_start_mem
544 When not otherwise constrained, this limits the memory start
546 The default is 0x80000000 and should be set to at least size of the
547 memory and not conflict with other resources.
548 Typically, only systems without PCI bridges need to set this variable
549 since PCI bridges typically constrain the memory starting address
550 (and the variable is only used when bridges do not constrain this
552 .It Va hw.pci.enable_io_modes
553 Enable PCI resources which are left off by some BIOSes or are not
554 enabled correctly by the device driver.
555 Tunable value set to ON (1) by default, but this may cause problems
556 with some peripherals.
558 Set the size of a number of statically allocated system tables; see
560 for a description of how to select an appropriate value for this
562 When set, this tunable replaces the value declared in the kernel
563 compile-time configuration file.
564 .It Va kern.ipc.nmbclusters
565 Set the number of mbuf clusters to be allocated.
566 The value cannot be set below the default
567 determined when the kernel was compiled.
568 .It Va kern.ipc.nsfbufs
571 buffers to be allocated.
574 Not all architectures use such buffers; see
577 .It Va kern.maxswzone
578 Limits the amount of KVM to be used to hold swap
579 meta information, which directly governs the
580 maximum amount of swap the system can support.
581 This value is specified in bytes of KVA space
582 and defaults to 32MBytes on i386 and amd64.
584 to not reduce this value such that the actual
585 amount of configured swap exceeds 1/2 the
586 kernel-supported swap.
587 The default of 32MB allows
588 the kernel to support a maximum of ~7GB of swap.
590 this parameter if you need to greatly extend the
591 KVM reservation for other resources such as the
593 .Va kern.ipc.nmbclusters .
594 Modifies kernel option
595 .Dv VM_SWZONE_SIZE_MAX .
596 .It Va kern.maxbcache
597 Limits the amount of KVM reserved for use by the
598 buffer cache, specified in bytes.
599 The default maximum is 200MB on i386,
600 and 400MB on amd64 and sparc64.
601 This parameter is used to
602 prevent the buffer cache from eating too much
603 KVM in large-memory machine configurations.
604 Only mess around with this parameter if you need to
605 greatly extend the KVM reservation for other resources
606 such as the swap zone or
607 .Va kern.ipc.nmbclusters .
609 the NBUF parameter will override this limit.
611 .Dv VM_BCACHE_SIZE_MAX .
612 .It Va kern.msgbufsize
613 Sets the size of the kernel message buffer.
614 The default limit of 64KB is usually sufficient unless
615 large amounts of trace data need to be collected
616 between opportunities to examine the buffer or
618 Overrides kernel option
620 .It Va machdep.disable_mtrrs
621 Disable the use of i686 MTRRs (x86 only).
622 .It Va net.inet.tcp.tcbhashsize
623 Overrides the compile-time set value of
625 or the preset default of 512.
626 Must be a power of 2.
628 Sets the size of kernel memory (bytes).
629 This overrides the value determined when the kernel was compiled.
632 .It Va vm.kmem_size_min
633 .It Va vm.kmem_size_max
634 Sets the minimum and maximum (respectively) amount of kernel memory
635 that will be automatically allocated by the kernel.
636 These override the values determined when the kernel was compiled.
640 .Dv VM_KMEM_SIZE_MAX .
643 When a builtin command is executed, the rest of the line is taken
644 by it as arguments, and it is processed by a special parser which
645 is not used for regular Forth commands.
647 This special parser applies the following rules to the parsed text:
650 All backslash characters are preprocessed.
653 \eb , \ef , \er , \en and \et are processed as in C.
655 \es is converted to a space.
662 Useful for things like
665 \e0xN and \e0xNN are replaced by the hex N or NN.
667 \eNNN is replaced by the octal NNN
671 \e" , \e' and \e$ will escape these characters, preventing them from
672 receiving special treatment in Step 2, described below.
674 \e\e will be replaced with a single \e .
676 In any other occurrence, backslash will just be removed.
679 Every string between non-escaped quotes or double-quotes will be treated
680 as a single word for the purposes of the remaining steps.
686 with the value of the environment variable
689 Space-delimited arguments are passed to the called builtin command.
690 Spaces can also be escaped through the use of \e\e .
693 An exception to this parsing rule exists, and is described in
694 .Sx BUILTINS AND FORTH .
695 .Ss BUILTINS AND FORTH
696 All builtin words are state-smart, immediate words.
697 If interpreted, they behave exactly as described previously.
698 If they are compiled, though,
699 they extract their arguments from the stack instead of the command line.
701 If compiled, the builtin words expect to find, at execution time, the
702 following parameters on the stack:
703 .D1 Ar addrN lenN ... addr2 len2 addr1 len1 N
706 are strings which will compose the command line that will be parsed
707 into the builtin's arguments.
708 Internally, these strings are concatenated in from 1 to N,
709 with a space put between each one.
711 If no arguments are passed, a 0
713 be passed, even if the builtin accepts no arguments.
715 While this behavior has benefits, it has its trade-offs.
716 If the execution token of a builtin is acquired (through
724 the builtin behavior will depend on the system state
732 This is particularly annoying for programs that want or need to
734 In this case, the use of a proxy is recommended.
739 is a Forth interpreter written in C, in the form of a forth
740 virtual machine library that can be called by C functions and vice
745 each line read interactively is then fed to
749 back to execute the builtin words.
756 The words available to
758 can be classified into four groups.
761 Forth standard words, extra
765 words, and the builtin commands;
766 the latter were already described.
769 Forth standard words are listed in the
772 The words falling in the two other groups are described in the
773 following subsections.
775 .Bl -tag -width wid-set-super
783 This is the STRING word set's
790 This is the STRING word set's
800 .Ss FREEBSD EXTRA WORDS
801 .Bl -tag -width XXXXXXXX
803 Evaluates the remainder of the input buffer, after having printed it first.
805 Evaluates the remainder of the input buffer under a
811 but without outputting a trailing space.
812 .It Ic fclose Pq Ar fd --
814 .It Ic fkey Pq Ar fd -- char
815 Reads a single character from a file.
816 .It Ic fload Pq Ar fd --
819 .It Ic fopen Pq Ar addr len mode Li -- Ar fd
821 Returns a file descriptor, or \-1 in case of failure.
824 parameter selects whether the file is to be opened for read access, write
827 .Dv O_RDONLY , O_WRONLY ,
831 .Pa /boot/support.4th ,
832 indicating read only, write only, and read-write access, respectively.
835 .Pq Ar fd addr len -- len'
843 Returns the actual number of bytes read, or -1 in case of error or end of
845 .It Ic heap? Pq -- Ar cells
846 Return the space remaining in the dictionary heap, in cells.
847 This is not related to the heap used by dynamic memory allocation words.
848 .It Ic inb Pq Ar port -- char
849 Reads a byte from a port.
850 .It Ic key Pq -- Ar char
851 Reads a single character from the console.
852 .It Ic key? Pq -- Ar flag
855 if there is a character available to be read from the console.
860 .It Ic outb Pq Ar port char --
861 Writes a byte to a port.
862 .It Ic seconds Pq -- Ar u
863 Returns the number of seconds since midnight.
864 .It Ic tib> Pq -- Ar addr len
865 Returns the remainder of the input buffer as a string on the stack.
866 .It Ic trace! Pq Ar flag --
867 Activates or deactivates tracing.
871 .Ss FREEBSD DEFINED ENVIRONMENTAL QUERIES
875 if the architecture is IA32.
878 version at compile time.
883 .Ss SYSTEM DOCUMENTATION
885 .Bl -tag -width /boot/defaults/loader.conf -compact
889 .It Pa /boot/boot.4th
893 .It Pa /boot/boot.conf
895 bootstrapping script.
897 .It Pa /boot/defaults/loader.conf
898 .It Pa /boot/loader.conf
899 .It Pa /boot/loader.conf.local
901 configuration files, as described in
903 .It Pa /boot/loader.rc
905 bootstrapping script.
906 .It Pa /boot/loader.help
909 Contains the help messages.
912 Boot in single user mode:
916 Load the kernel, a splash screen, and then autoboot in five seconds.
917 Notice that a kernel must be loaded before any other
919 command is attempted.
920 .Bd -literal -offset indent
923 load -t splash_image_data /boot/chuckrulez.bmp
927 Set the disk unit of the root device to 2, and then boot.
928 This would be needed in a system with two IDE disks,
929 with the second IDE disk hardwired to wd2 instead of wd1.
930 .Bd -literal -offset indent
936 .Bl -tag -width /usr/share/examples/bootforth/X
937 .It Pa /boot/loader.4th
938 Extra builtin-like words.
939 .It Pa /boot/support.4th
942 .It Pa /usr/share/examples/bootforth/
946 The following values are thrown by
948 .Bl -tag -width XXXXX -offset indent
950 Any type of error in the processing of a builtin.
961 Out of interpreting text.
963 Need more text to succeed -- will finish on next run.
977 For the purposes of ANS Forth compliance, loader is an
979 ANS Forth System with Environmental Restrictions, Providing
985 parse, pick, roll, refill, to, value, \e, false, true,
988 compile\&, , erase, nip, tuck
993 from the Core Extensions word set, Providing the Exception Extensions
994 word set, Providing the Locals Extensions word set, Providing the
995 Memory-Allocation Extensions word set, Providing
999 bye, forget, see, words,
1006 from the Programming-Tools extension word set, Providing the
1007 Search-Order extensions word set.
1019 .An Michael Smith Aq msmith@FreeBSD.org .
1023 .An John Sadler Aq john_sadler@alum.mit.edu .
1029 words will read from the input buffer instead of the console.
1030 The latter will be fixed, but the former will not.
projects / FreeBSD / releng / 9.0.git / blob