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 devices with known file systems, where a
250 '*' prefix indicates a device from which it may be
251 possible to load modules.
254 is specified, more details are printed.
257 Displays loaded modules.
260 is specified, more details are shown.
262 .It Ic more Ar file Op Ar
263 Display the files specified, with a pause at each
267 .It Ic pnpscan Op Fl v
268 Scans for Plug-and-Play devices.
269 This is not functional at present.
276 Reads a line of input from the terminal, storing it in
279 A timeout can be specified with
281 though it will be canceled at the first key pressed.
282 A prompt may also be displayed through the
287 Immediately reboots the system.
289 .It Ic set Ar variable
290 .It Ic set Ar variable Ns = Ns Ar value
291 Set loader's environment variables.
293 .It Ic show Op Va variable
294 Displays the specified variable's value, or all variables and their
300 Remove all modules from memory.
302 .It Ic unset Va variable
305 from the environment.
311 .Ss BUILTIN ENVIRONMENT VARIABLES
314 has actually two different kinds of
317 There are ANS Forth's
318 .Em environmental queries ,
319 and a separate space of environment variables used by builtins, which
320 are not directly available to Forth words.
321 It is the latter type that this section covers.
323 Environment variables can be set and unset through the
327 builtins, and can have their values interactively examined through the
331 Their values can also be accessed as described in
334 Notice that these environment variables are not inherited by any shell
335 after the system has been booted.
337 A few variables are set automatically by
339 Others can affect the behavior of either
341 or the kernel at boot.
342 Some options may require a value,
343 while others define behavior just by being set.
344 Both types of builtin variables are described below.
345 .Bl -tag -width bootfile
347 Unset this to disable automatic loading of the ACPI module.
348 .It Va autoboot_delay
351 will wait before booting.
352 If this variable is not defined,
354 will default to 10 seconds.
360 will be automatically attempted after processing
364 will be processed normally, defaulting to 10 seconds delay.
366 Instructs the kernel to prompt the user for the name of the root device
367 when the kernel is booted.
369 Instructs the kernel to start in the DDB debugger, rather than
370 proceeding to initialize when booted.
372 Selects gdb-remote mode for the kernel debugger by default.
374 Prevents the kernel from initiating a multi-user startup; instead single-user
375 mode will be entered when the kernel has finished device probing.
376 .It Va boot_userconfig
377 Requests that the kernel's interactive device configuration program
378 be run when the kernel is booted.
380 Setting this variable causes extra debugging information to be printed
381 by the kernel during the boot phase.
383 List of semicolon-separated search path for bootable kernels.
385 .Dq Li kernel;kernel.old .
387 Defines the current console.
389 Selects the default device.
390 Syntax for devices is odd.
392 Sets the list of binaries which the kernel will try to run as the initial
394 The first matching binary is used.
396 .Dq Li /sbin/init:/sbin/oinit:/sbin/init.bak .
400 if the Forth's current state is interpreting.
402 Define the number of lines on the screen, to be used by the pager.
404 Sets the list of directories which will be searched for modules
405 named in a load command or implicitly required by a dependency.
406 The default value for this variable is
407 .Dq Li /boot;/boot/modules;/;/modules .
409 Sets the number of IDE disks as a workaround for some problems in
410 finding the root disk at boot.
411 This has been deprecated in favor of
418 .Dq Li "\e${interpret}" .
419 .It Va root_disk_unit
420 If the code which detects the disk unit number for the root disk is
421 confused, e.g. by a mix of SCSI and IDE disks, or IDE disks with
422 gaps in the sequence (e.g. no primary slave), the unit number can
423 be forced by setting this variable.
425 By default the value of
427 is used to set the root file system
428 when the kernel is booted.
429 This can be overridden by setting
433 The name of a device where the kernel can save a crash dump in case
435 This automatically sets the
441 Other variables are used to override kernel tunable parameters.
444 tunables are available:
447 Set irqX's destination to the given CPUID,
449 If the specified value is larger than the last CPUID,
450 then the first CPUID will be used.
451 This variable should not be used if IO/APIC support is not compiled
454 Limit the amount of physical memory the system will use.
455 By default the size is in bytes, but the
456 .Cm k , K , m , M , g
460 are also accepted and indicate kilobytes, megabytes and gigabytes
462 An invalid suffix will result in the variable being ignored by the
464 .It Va hw.usb.hack_defer_exploration
465 The USB keyboard will sometimes not attach properly unless you set this
467 .It Va kern.emergency_intr_enable
468 Setting this to 1 enables emergency interrupt polling. All interrupt
469 handlers are executed periodically. This mode is very expensive and should
470 only be used to get a system accessible when interrupt routing is
471 otherwise broken. It is primarily used by kernel developers to debug new
473 .It Va kern.emergency_intr_freq
474 Set the polling rate for the emergency interrupt polling code. The
475 default is 10 (hz) to dissuade casual use. If you are doing real work
476 with emergency interrupt polling mode enabled, it is recommended
477 that you use a frequency between 100hz and 300hz.
479 Set the size of a number of statically allocated system tables; see
481 for a description of how to select an appropriate value for this
483 When set, this tunable replaces the value declared in the kernel
484 compile-time configuration file.
485 .It Va kern.ipc.nmbclusters
486 Set the number of mbuf clusters to be allocated.
487 The value cannot be set below the default
488 determined when the kernel was compiled.
491 .It Va kern.ipc.nsfbufs
494 buffers to be allocated.
498 Toggles the mmx optimizations for the bcopy/copyin/copyout routines
499 .It Va kern.vm.kmem.size
500 Sets the size of kernel memory (bytes).
501 This overrides the value determined when the kernel was compiled.
502 .It Va kern.maxswzone
503 Limits the amount of KVM to be used to hold swap
504 meta information, which directly governs the
505 maximum amount of swap the system can support.
506 This value is specified in bytes of KVA space
507 and defaults to around 70MBytes.
509 to not reduce this value such that the actual
510 amount of configured swap exceeds \(12 the
511 kernel-supported swap.
512 The default 70MB allows
513 the kernel to support a maximum of (approximately)
514 14GB of configured swap.
515 Only mess around with
516 this parameter if you need to greatly extend the
517 KVM reservation for other resources such as the
521 .Va VM_SWZONE_SIZE_MAX .
522 .It Va kern.maxbcache
523 Limits the amount of KVM reserved for use by the
524 buffer cache, specified in bytes.
525 The default maximum is 200MB.
526 This parameter is used to
527 prevent the buffer cache from eating too much
528 KVM in large-memory machine configurations.
529 Only mess around with this parameter if you need to
530 greatly extend the KVM reservation for other resources
531 such as the swap zone or
534 the NBUF parameter will override this limit.
536 .Va VM_BCACHE_SIZE_MAX .
537 .It Va machdep.disable_mtrrs
538 Disable the use of i686 MTRRs (x86 only).
539 .It Va net.inet.tcp.tcbhashsize
540 Overrides the compile-time set value of
542 or the preset default of 512.
543 Must be a power of 2.
544 .It Va vfs.root.mountfrom
545 A semicolon separated list of partitions to try
546 as the kernel root file system.
547 Device format is file system type and partition,
549 Used with boot-only partition, which is
550 typically mounted on root file system as
554 One device example: "hammer:da8s1a"
556 Several devices example: "ufs:da0s1a;hammer:ad1s1d"
559 Each device in the list will be tried in the order specified
560 until the mount succeeds.
563 prompt is displayed for manual entry.
565 You may not specify devtab labels here but you can specify paths available
566 to devfs such as "hammer:serno/L41JYE0G.s1d".
569 When a builtin command is executed, the rest of the line is taken
570 by it as arguments, and it is processed by a special parser which
571 is not used for regular Forth commands.
573 This special parser applies the following rules to the parsed text:
576 All backslash characters are preprocessed.
579 \eb , \ef , \er , \en and \et are processed as in C.
581 \es is converted to a space.
588 Useful for things like
591 \e0xN and \e0xNN are replaced by the hex N or NN.
593 \eNNN is replaced by the octal NNN
597 \e" , \e' and \e$ will escape these characters, preventing them from
598 receiving special treatment in Step 2, described below.
600 \e\e will be replaced with a single \e .
602 In any other occurrence, backslash will just be removed.
605 Every string between non-escaped quotes or double-quotes will be treated
606 as a single word for the purposes of the remaining steps.
612 with the value of the environment variable
615 Space-delimited arguments are passed to the called builtin command.
616 Spaces can also be escaped through the use of \e\e .
619 An exception to this parsing rule exists, and is described in
620 .Sx BUILTINS AND FORTH .
621 .Ss BUILTINS AND FORTH
622 All builtin words are state-smart, immediate words.
623 If interpreted, they behave exactly as described previously.
624 If they are compiled, though,
625 they extract their arguments from the stack instead of the command line.
627 If compiled, the builtin words expect to find, at execution time, the
628 following parameters on the stack:
629 .D1 Ar addrN lenN ... addr2 len2 addr1 len1 N
632 are strings which will compose the command line that will be parsed
633 into the builtin's arguments.
634 Internally, these strings are concatenated in from 1 to N,
635 with a space put between each one.
637 If no arguments are passed, a 0
639 be passed, even if the builtin accepts no arguments.
641 While this behavior has benefits, it has its trade-offs.
642 If the execution token of a builtin is acquired (through
650 the builtin behavior will depend on the system state
658 \&! This is particularly annoying for programs that want or need to
660 In this case, the use of a proxy is recommended.
662 .Dl : (boot) boot \&;
665 is a Forth interpreter written in C, in the form of a forth
666 virtual machine library that can be called by C functions and vice
671 each line read interactively is then fed to
675 back to execute the builtin words.
682 The words available to
684 can be classified into four groups.
687 Forth standard words, extra
691 words, and the builtin commands;
692 the latter were already described.
695 Forth standard words are listed in the
698 The words falling in the two other groups are described in the
699 following subsections.
701 .Bl -tag -width wid-set-super
709 This is the STRING word set's
716 This is the STRING word set's
726 .Ss DRAGONFLY EXTRA WORDS
727 .Bl -tag -width XXXXXXXX
729 Evaluates the remainder of the input buffer, after having printed it first.
731 Evaluates the remainder of the input buffer under a
737 but without outputting a trailing space.
738 .It Ic fclose Pq Ar fd --
740 .It Ic fkey Pq Ar fd -- char
741 Reads a single character from a file.
742 .It Ic fload Pq Ar fd --
745 .It Ic fopen Pq Ar addr len mode Li -- Ar fd
747 Returns a file descriptor, or \-1 in case of failure.
750 parameter selects whether the file is to be opened for read access, write
753 .Dv O_RDONLY , O_WRONLY ,
758 indicating read only, write only, and read-write access, respectively.
761 .Pq Ar fd addr len -- len'
769 Returns the actual number of bytes read, or -1 in case of error or end of
771 .It Ic heap? Pq -- Ar cells
772 Return the space remaining in the dictionary heap, in cells.
773 This is not related to the heap used by dynamic memory allocation words.
774 .It Ic inb Pq Ar port -- char
775 Reads a byte from a port.
776 .It Ic key Pq -- Ar char
777 Reads a single character from the console.
778 .It Ic key? Pq -- Ar flag
781 if there is a character available to be read from the console.
786 .It Ic outb Pq Ar port char --
787 Writes a byte to a port.
788 .It Ic seconds Pq -- Ar u
789 Returns the number of seconds since midnight.
790 .It Ic tib> Pq -- Ar addr len
791 Returns the remainder of the input buffer as a string on the stack.
792 .It Ic trace! Pq Ar flag --
793 Activates or deactivates tracing.
797 .Ss DRAGONFLY DEFINED ENVIRONMENTAL QUERIES
801 if the architecture is IA32.
802 .It DragonFly_version
804 version at compile time.
809 .Ss SYSTEM DOCUMENTATION
811 .Bl -tag -width /boot/defaults/loader.conf -compact
815 .It Pa /boot/boot.4th
819 .It Pa /boot/boot.conf
821 bootstrapping script.
823 .It Pa /boot/defaults/loader.conf
824 .It Pa /boot/loader.conf
825 .It Pa /boot/loader.conf.local
827 configuration files, as described in
829 .It Pa /boot/loader.rc
831 bootstrapping script.
832 .It Pa /boot/loader.help
835 Contains the help messages.
838 Boot in single user mode:
842 Load kernel's user configuration file.
843 Notice that a kernel must be loaded before any other
845 command is attempted.
846 .Bd -literal -offset indent
848 load -t userconfig_script kernel.conf
851 Load the kernel, a splash screen, and then autoboot in five seconds.
852 .Bd -literal -offset indent
855 load -t splash_image_data chuckrulez.bmp
859 Set the disk unit of the root device to 2, and then boot.
860 This would be needed in a system with two IDE disks,
861 with the second IDE disk hardwired to ad2 instead of ad1.
862 .Bd -literal -offset indent
868 .Bl -tag -width /usr/share/examples/bootforth/X
870 Extra builtin-like words.
874 .It Pa /usr/share/examples/bootforth/
878 The following values are thrown by
880 .Bl -tag -width XXXXX -offset indent
882 Any type of error in the processing of a builtin.
893 Out of interpreting text.
895 Need more text to succeed -- will finish on next run.
911 For the purposes of ANS Forth compliance, loader is an
913 ANS Forth System with Environmental Restrictions, Providing
919 parse, pick, roll, refill, to, value, \e, false, true,
922 compile\&, , erase, nip, tuck
927 from the Core Extensions word set, Providing the Exception Extensions
928 word set, Providing the Locals Extensions word set, Providing the
929 Memory-Allocation Extensions word set, Providing
933 bye, forget, see, words,
940 from the Programming-Tools extension word set, Providing the
941 Search-Order extensions word set.
953 .An Michael Smith Aq msmith@FreeBSD.org .
957 .An John Sadler Aq john_sadler@alum.mit.edu .
963 words will read from the input buffer instead of the console.
964 The latter will be fixed, but the former will not.
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