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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.
422 .It Va comconsole_port
423 Defines the base i/o port used to access console UART
424 (i386 and amd64 only).
425 If the variable is not set, its assumed value is 0x3F8, which
426 corresponds to PC port COM1, unless overridden by
427 .Va BOOT_COMCONSOLE_PORT
428 variable during the compilation of
432 variable automatically set
434 environment variable to provide a hint to kernel for location of the console.
435 Loader console is changed immediately after variable
438 .It Va comconsole_pcidev
439 Defines the location of a PCI device of the 'simple communication'
440 class to be used as the serial console UART (i386 and amd64 only).
441 The syntax of the variable is
442 .Li 'bus:device:function[:bar]' ,
443 where all members must be numeric, with possible
445 prefix to indicate a hexadecimal value.
448 member is optional and assumed to be 0x10 if omitted.
449 The bar must decode i/o space.
451 .Va comconsole_pcidev
452 automatically sets the variable
454 to the base of the selected bar, and hint
455 .Va hw.uart.console .
456 Loader console is changed immediately after variable
457 .Va comconsole_pcidev
460 Defines the current console or consoles.
461 Multiple consoles may be specified.
462 In that case, the first listed console will become the default console for
463 userland output (e.g.\& from
466 Selects the default device.
467 Syntax for devices is odd.
469 If set to a valid directory in the root file system, it causes
473 operation on that directory, making it the new root directory.
474 That happens before entering single-user mode or multi-user
475 mode (but after executing the
479 Sets the list of binaries which the kernel will try to run as the initial
481 The first matching binary is used.
483 .Dq Li /sbin/init:/sbin/oinit:/sbin/init.bak:\:/rescue/init:/stand/sysinstall .
485 If set to a valid file name in the root file system,
488 to run that script as the very first action,
489 before doing anything else.
490 Signal handling and exit code interpretation is similar to
494 In particular, single-user operation is enforced
495 if the script terminates with a non-zero exit code,
496 or if a SIGTERM is delivered to the
500 Defines the shell binary to be used for executing the various shell scripts.
503 It is used for running the
505 if set, as well as for the
510 The value of the corresponding
512 variable is evaluated every time
514 calls a shell script, so it can be changed later on using the
517 In particular, if a non-default shell is used for running an
519 it might be desirable to have that script reset the value of
521 back to the default, so that the
523 script is executed with the standard shell
528 if the Forth's current state is interpreting.
530 Define the number of lines on the screen, to be used by the pager.
532 Sets the list of directories which will be searched for modules
533 named in a load command or implicitly required by a dependency.
534 The default value for this variable is
535 .Dq Li /boot/kernel;/boot/modules .
537 Sets the number of IDE disks as a workaround for some problems in
538 finding the root disk at boot.
539 This has been deprecated in favor of
546 .Dq Li "${interpret}" .
549 is unset, the default prompt is
551 .It Va root_disk_unit
552 If the code which detects the disk unit number for the root disk is
553 confused, e.g.\& by a mix of SCSI and IDE disks, or IDE disks with
554 gaps in the sequence (e.g.\& no primary slave), the unit number can
555 be forced by setting this variable.
557 By default the value of
559 is used to set the root file system
560 when the kernel is booted.
561 This can be overridden by setting
566 Other variables are used to override kernel tunable parameters.
567 The following tunables are available:
570 Limit the amount of physical memory the system will use.
571 By default the size is in bytes, but the
572 .Cm k , K , m , M , g
576 are also accepted and indicate kilobytes, megabytes and gigabytes
578 An invalid suffix will result in the variable being ignored by the
580 .It Va hw.pci.host_start_mem , hw.acpi.host_start_mem
581 When not otherwise constrained, this limits the memory start
583 The default is 0x80000000 and should be set to at least size of the
584 memory and not conflict with other resources.
585 Typically, only systems without PCI bridges need to set this variable
586 since PCI bridges typically constrain the memory starting address
587 (and the variable is only used when bridges do not constrain this
589 .It Va hw.pci.enable_io_modes
590 Enable PCI resources which are left off by some BIOSes or are not
591 enabled correctly by the device driver.
592 Tunable value set to ON (1) by default, but this may cause problems
593 with some peripherals.
595 Set the size of a number of statically allocated system tables; see
597 for a description of how to select an appropriate value for this
599 When set, this tunable replaces the value declared in the kernel
600 compile-time configuration file.
601 .It Va kern.ipc.nmbclusters
602 Set the number of mbuf clusters to be allocated.
603 The value cannot be set below the default
604 determined when the kernel was compiled.
605 .It Va kern.ipc.nsfbufs
608 buffers to be allocated.
611 Not all architectures use such buffers; see
614 .It Va kern.maxswzone
615 Limits the amount of KVM to be used to hold swap
616 meta information, which directly governs the
617 maximum amount of swap the system can support.
618 This value is specified in bytes of KVA space
619 and defaults to 32MBytes on i386 and amd64.
621 to not reduce this value such that the actual
622 amount of configured swap exceeds 1/2 the
623 kernel-supported swap.
624 The default of 32MB allows
625 the kernel to support a maximum of ~7GB of swap.
627 this parameter if you need to greatly extend the
628 KVM reservation for other resources such as the
630 .Va kern.ipc.nmbclusters .
631 Modifies kernel option
632 .Dv VM_SWZONE_SIZE_MAX .
633 .It Va kern.maxbcache
634 Limits the amount of KVM reserved for use by the
635 buffer cache, specified in bytes.
636 The default maximum is 200MB on i386,
637 and 400MB on amd64 and sparc64.
638 This parameter is used to
639 prevent the buffer cache from eating too much
640 KVM in large-memory machine configurations.
641 Only mess around with this parameter if you need to
642 greatly extend the KVM reservation for other resources
643 such as the swap zone or
644 .Va kern.ipc.nmbclusters .
646 the NBUF parameter will override this limit.
648 .Dv VM_BCACHE_SIZE_MAX .
649 .It Va kern.msgbufsize
650 Sets the size of the kernel message buffer.
651 The default limit of 64KB is usually sufficient unless
652 large amounts of trace data need to be collected
653 between opportunities to examine the buffer or
655 Overrides kernel option
657 .It Va machdep.disable_mtrrs
658 Disable the use of i686 MTRRs (x86 only).
659 .It Va net.inet.tcp.tcbhashsize
660 Overrides the compile-time set value of
662 or the preset default of 512.
663 Must be a power of 2.
665 Sets the size of kernel memory (bytes).
666 This overrides the value determined when the kernel was compiled.
669 .It Va vm.kmem_size_min
670 .It Va vm.kmem_size_max
671 Sets the minimum and maximum (respectively) amount of kernel memory
672 that will be automatically allocated by the kernel.
673 These override the values determined when the kernel was compiled.
677 .Dv VM_KMEM_SIZE_MAX .
680 When a builtin command is executed, the rest of the line is taken
681 by it as arguments, and it is processed by a special parser which
682 is not used for regular Forth commands.
684 This special parser applies the following rules to the parsed text:
687 All backslash characters are preprocessed.
690 \eb , \ef , \er , \en and \et are processed as in C.
692 \es is converted to a space.
699 Useful for things like
702 \e0xN and \e0xNN are replaced by the hex N or NN.
704 \eNNN is replaced by the octal NNN
708 \e" , \e' and \e$ will escape these characters, preventing them from
709 receiving special treatment in Step 2, described below.
711 \e\e will be replaced with a single \e .
713 In any other occurrence, backslash will just be removed.
716 Every string between non-escaped quotes or double-quotes will be treated
717 as a single word for the purposes of the remaining steps.
723 with the value of the environment variable
726 Space-delimited arguments are passed to the called builtin command.
727 Spaces can also be escaped through the use of \e\e .
730 An exception to this parsing rule exists, and is described in
731 .Sx BUILTINS AND FORTH .
732 .Ss BUILTINS AND FORTH
733 All builtin words are state-smart, immediate words.
734 If interpreted, they behave exactly as described previously.
735 If they are compiled, though,
736 they extract their arguments from the stack instead of the command line.
738 If compiled, the builtin words expect to find, at execution time, the
739 following parameters on the stack:
740 .D1 Ar addrN lenN ... addr2 len2 addr1 len1 N
743 are strings which will compose the command line that will be parsed
744 into the builtin's arguments.
745 Internally, these strings are concatenated in from 1 to N,
746 with a space put between each one.
748 If no arguments are passed, a 0
750 be passed, even if the builtin accepts no arguments.
752 While this behavior has benefits, it has its trade-offs.
753 If the execution token of a builtin is acquired (through
761 the builtin behavior will depend on the system state
769 This is particularly annoying for programs that want or need to
771 In this case, the use of a proxy is recommended.
776 is a Forth interpreter written in C, in the form of a forth
777 virtual machine library that can be called by C functions and vice
782 each line read interactively is then fed to
786 back to execute the builtin words.
793 The words available to
795 can be classified into four groups.
798 Forth standard words, extra
802 words, and the builtin commands;
803 the latter were already described.
806 Forth standard words are listed in the
809 The words falling in the two other groups are described in the
810 following subsections.
812 .Bl -tag -width wid-set-super
820 This is the STRING word set's
827 This is the STRING word set's
837 .Ss FREEBSD EXTRA WORDS
838 .Bl -tag -width XXXXXXXX
840 Evaluates the remainder of the input buffer, after having printed it first.
842 Evaluates the remainder of the input buffer under a
848 but without outputting a trailing space.
849 .It Ic fclose Pq Ar fd --
851 .It Ic fkey Pq Ar fd -- char
852 Reads a single character from a file.
853 .It Ic fload Pq Ar fd --
856 .It Ic fopen Pq Ar addr len mode Li -- Ar fd
858 Returns a file descriptor, or \-1 in case of failure.
861 parameter selects whether the file is to be opened for read access, write
864 .Dv O_RDONLY , O_WRONLY ,
868 .Pa /boot/support.4th ,
869 indicating read only, write only, and read-write access, respectively.
872 .Pq Ar fd addr len -- len'
880 Returns the actual number of bytes read, or -1 in case of error or end of
882 .It Ic heap? Pq -- Ar cells
883 Return the space remaining in the dictionary heap, in cells.
884 This is not related to the heap used by dynamic memory allocation words.
885 .It Ic inb Pq Ar port -- char
886 Reads a byte from a port.
887 .It Ic key Pq -- Ar char
888 Reads a single character from the console.
889 .It Ic key? Pq -- Ar flag
892 if there is a character available to be read from the console.
897 .It Ic outb Pq Ar port char --
898 Writes a byte to a port.
899 .It Ic seconds Pq -- Ar u
900 Returns the number of seconds since midnight.
901 .It Ic tib> Pq -- Ar addr len
902 Returns the remainder of the input buffer as a string on the stack.
903 .It Ic trace! Pq Ar flag --
904 Activates or deactivates tracing.
908 .Ss FREEBSD DEFINED ENVIRONMENTAL QUERIES
912 if the architecture is IA32.
915 version at compile time.
920 .Ss SYSTEM DOCUMENTATION
922 .Bl -tag -width /boot/defaults/loader.conf -compact
926 .It Pa /boot/boot.4th
930 .It Pa /boot/boot.conf
932 bootstrapping script.
934 .It Pa /boot/defaults/loader.conf
935 .It Pa /boot/loader.conf
936 .It Pa /boot/loader.conf.local
938 configuration files, as described in
940 .It Pa /boot/loader.rc
942 bootstrapping script.
943 .It Pa /boot/loader.help
946 Contains the help messages.
949 Boot in single user mode:
953 Load the kernel, a splash screen, and then autoboot in five seconds.
954 Notice that a kernel must be loaded before any other
956 command is attempted.
957 .Bd -literal -offset indent
960 load -t splash_image_data /boot/chuckrulez.bmp
964 Set the disk unit of the root device to 2, and then boot.
965 This would be needed in a system with two IDE disks,
966 with the second IDE disk hardwired to ad2 instead of ad1.
967 .Bd -literal -offset indent
969 boot /boot/kernel/kernel
973 .Bl -tag -width /usr/share/examples/bootforth/X
974 .It Pa /boot/loader.4th
975 Extra builtin-like words.
976 .It Pa /boot/support.4th
979 .It Pa /usr/share/examples/bootforth/
983 The following values are thrown by
985 .Bl -tag -width XXXXX -offset indent
987 Any type of error in the processing of a builtin.
998 Out of interpreting text.
1000 Need more text to succeed -- will finish on next run.
1014 For the purposes of ANS Forth compliance, loader is an
1016 ANS Forth System with Environmental Restrictions, Providing
1022 parse, pick, roll, refill, to, value, \e, false, true,
1025 compile\&, , erase, nip, tuck
1030 from the Core Extensions word set, Providing the Exception Extensions
1031 word set, Providing the Locals Extensions word set, Providing the
1032 Memory-Allocation Extensions word set, Providing
1036 bye, forget, see, words,
1043 from the Programming-Tools extension word set, Providing the
1044 Search-Order extensions word set.
1056 .An Michael Smith Aq msmith@FreeBSD.org .
1060 .An John Sadler Aq john_sadler@alum.mit.edu .
1066 words will read from the input buffer instead of the console.
1067 The latter will be fixed, but the former will not.
projects / FreeBSD / stable / 9.git / blob