DragonFly On-Line Manual Pages
LOADER(8) DragonFly System Manager's Manual LOADER(8)
NAME
loader -- kernel bootstrapping final stage
DESCRIPTION
The program called loader is the final stage of DragonFly's kernel boot-
strapping process. On IA32 (i386) architectures, it is a BTX client. It
is linked statically to libstand(3) and located in the /boot or / direc-
tory.
If a /boot directory exist on the boot file system, then ``/boot/'' is
prepended to all relative file names used by loader. This makes it pos-
sible to locate all files used by loader in either / or /boot directory
on the boot file system. If boot and root are the same file systems,
then files used by loader are located in /boot. If boot and root are
different file systems, then files used by loader are located in / on the
boot file system, which is mounted as /boot on the root file system when
the kernel is running.
loader provides a scripting language that can be used to automate tasks,
do pre-configuration or assist in recovery procedures. This scripting
language is roughly divided in two main components. The smaller one is a
set of commands designed for direct use by the casual user, called
"builtin commands" for historical reasons. The main drive behind these
commands is user-friendliness. The bigger component is an ANS Forth com-
patible Forth interpreter based on FICL, by John Sadler.
During initialization, loader will probe for a console and set the
console variable, or set it to serial console (``comconsole'') if the
previous boot stage used that. Then, devices are probed, currdev and
loaddev are set, and LINES is set to 24. Next, FICL is initialized, the
builtin words are added to its vocabulary, and boot.4th is processed if
it exists. No disk switching is possible while that file is being read.
The inner interpreter loader will use with FICL is then set to interpret,
which is FICL's default. After that, loader.rc is processed if avail-
able, and, failing that, boot.conf is read for historical reasons. These
files are processed through the include command, which reads all of them
into memory before processing them, making disk changes possible.
At this point, if an autoboot has not been tried, and if autoboot_delay
is not set to ``NO'' (not case sensitive), then an autoboot will be
tried. If the system gets past this point, prompt will be set and loader
will engage interactive mode.
BUILTIN COMMANDS
In loader, builtin commands take parameters from the command line.
Presently, the only way to call them from a script is by using evaluate
on a string. If an error condition occurs, an exception will be gener-
ated, which can be intercepted using ANS Forth exception handling words.
If not intercepted, an error message will be displayed and the inter-
preter's state will be reset, emptying the stack and restoring interpret-
ing mode.
The builtin commands available are:
autoboot [seconds]
Proceeds to bootstrap the system after a number of seconds, if
not interrupted by the user. Displays a countdown prompt warning
the user the system is about to be booted, unless interrupted by
a key press. The kernel will be loaded first if necessary.
Defaults to 10 seconds.
bcachestat
Displays statistics about disk cache usage. For depuration only.
boot
boot kernelname [...]
boot -flag ...
Immediately proceeds to bootstrap the system, loading the kernel
if necessary. Any flags or arguments are passed to the kernel,
but they must precede the kernel name, if a kernel name is pro-
vided. Flags are described in boot(8).
echo [-n] [<message>]
Displays text on the screen. A new line will be printed unless
-n is specified.
heap Displays memory usage statistics. For debugging purposes only.
help [topic [subtopic]]
Shows help messages read from loader.help. The special topic
index will list the topics available.
include file [file ...]
Process script files. Each file, in turn, is completely read
into memory, and then each of its lines is passed to the command
line interpreter. If any error is returned by the interpreter,
the include command aborts immediately, without reading any other
files, and returns an error itself (see ERRORS).
load [-t type] file ...
Loads a kernel, kernel loadable module (kld), or file of opaque
contents tagged as being of the type type. Kernel and modules
can be either in a.out or ELF format. Any arguments passed after
the name of the file to be loaded will be passed as arguments to
that file. Currently, argument passing does not work for the
kernel.
ls [-l] [path]
Displays a listing of files in the directory path, or the root
directory if path is not specified. If -l is specified, file
sizes will be shown too.
lsdev [-v]
Lists all devices with known file systems, where a `*' prefix
indicates a device from which it may be possible to load modules.
If -v is specified, more details are printed.
lsmod [-v]
Displays loaded modules. If -v is specified, more details are
shown.
more file [file ...]
Display the files specified, with a pause at each LINES dis-
played.
pnpscan [-v]
Scans for Plug-and-Play devices. This is not functional at
present.
read [-t seconds] [-p prompt] [variable]
Reads a line of input from the terminal, storing it in variable
if specified. A timeout can be specified with -t, though it will
be canceled at the first key pressed. A prompt may also be dis-
played through the -p flag.
reboot Immediately reboots the system.
set variable
set variable=value
Set loader's environment variables.
show [variable]
Displays the specified variable's value, or all variables and
their values if variable is not specified.
unload Remove all modules from memory.
unset variable
Removes variable from the environment.
? Same as ``help index''.
BUILTIN ENVIRONMENT VARIABLES
The loader has actually two different kinds of `environment' variables.
There are ANS Forth's environmental queries, and a separate space of
environment variables used by builtins, which are not directly available
to Forth words. It is the latter type that this section covers.
Environment variables can be set and unset through the set and unset
builtins, and can have their values interactively examined through the
use of the show builtin. Their values can also be accessed as described
in BUILTIN PARSER.
Notice that these environment variables are not inherited by any shell
after the system has been booted.
A few variables are set automatically by loader. Others can affect the
behavior of either loader or the kernel at boot. Some options may
require a value, while others define behavior just by being set. Both
types of builtin variables are described below.
acpi_load
Unset this to disable automatic loading of the ACPI module.
autoboot_delay
Number of seconds autoboot will wait before booting. If this
variable is not defined, autoboot will default to 10 seconds.
If set to ``NO'', no autoboot will be automatically attempted
after processing loader.rc, though explicit autoboot's will be
processed normally, defaulting to 10 seconds delay.
boot_askname
Instructs the kernel to prompt the user for the name of the
root device when the kernel is booted.
boot_ddb Instructs the kernel to start in the DDB debugger, rather than
proceeding to initialize when booted.
boot_gdb Selects gdb-remote mode for the kernel debugger by default.
boot_single
Prevents the kernel from initiating a multi-user startup;
instead single-user mode will be entered when the kernel has
finished device probing.
boot_userconfig
Requests that the kernel's interactive device configuration
program be run when the kernel is booted.
boot_verbose
Setting this variable causes extra debugging information to be
printed by the kernel during the boot phase.
bootfile List of semicolon-separated search path for bootable kernels.
The default is ``kernel;kernel.old''.
console Defines the current console.
currdev Selects the default device. Syntax for devices is odd.
ehci_load
Unset this to disable automatic loading of the EHCI module.
init_path
Sets the list of binaries which the kernel will try to run as
the initial process. The first matching binary is used. The
default list is ``/sbin/init:/sbin/oinit:/sbin/init.bak''.
interpret
Has the value ``OK'' if the Forth's current state is interpret-
ing.
LINES Define the number of lines on the screen, to be used by the
pager.
module_path
Sets the list of directories which will be searched for modules
named in a load command or implicitly required by a dependency.
The default value for this variable is
``/boot;/boot/modules;/;/modules''.
num_ide_disks
Sets the number of IDE disks as a workaround for some problems
in finding the root disk at boot. This has been deprecated in
favor of root_disk_unit.
prompt Value of loader's prompt. Defaults to ``\${interpret}''.
root_disk_unit
If the code which detects the disk unit number for the root
disk is confused, e.g. by a mix of SCSI and IDE disks, or IDE
disks with gaps in the sequence (e.g. no primary slave), the
unit number can be forced by setting this variable.
rootdev By default the value of currdev is used to set the root file
system when the kernel is booted. This can be overridden by
setting rootdev explicitly.
dumpdev The name of a device where the kernel can save a crash dump in
case of a panic. This automatically sets the kern.dumpdev
sysctl(3) MIB variable.
Other variables are used to override kernel tunable parameters. The fol-
lowing loader tunables are available:
hw.irq.X.dest
Set irqX's destination to the given CPUID, which starts
from 0. If the specified value is larger than the last
CPUID, then the first CPUID will be used. This variable
should not be used if IO/APIC support is not compiled into
kernel.
hw.physmem Limit the amount of physical memory the system will use.
By default the size is in bytes, but the k, K, m, M, g and
G suffixes are also accepted and indicate kilobytes,
megabytes and gigabytes respectively. An invalid suffix
will result in the variable being ignored by the kernel.
hw.usb.hack_defer_exploration
The USB keyboard will sometimes not attach properly unless
you set this variable to 0.
kern.emergency_intr_enable
Setting this to 1 enables emergency interrupt polling. All
interrupt handlers are executed periodically. This mode is
very expensive and should only be used to get a system
accessible when interrupt routing is otherwise broken. It
is primarily used by kernel developers to debug new sys-
tems.
kern.emergency_intr_freq
Set the polling rate for the emergency interrupt polling
code. The default is 10 (hz) to dissuade casual use. If
you are doing real work with emergency interrupt polling
mode enabled, it is recommended that you use a frequency
between 100hz and 300hz.
kern.maxusers
Set the size of a number of statically allocated system
tables; see tuning(7) for a description of how to select an
appropriate value for this tunable. When set, this tunable
replaces the value declared in the kernel compile-time con-
figuration file.
kern.ipc.nmbclusters
Set the number of mbuf clusters to be allocated. The value
cannot be set below the default determined when the kernel
was compiled. Modifies NMBCLUSTERS.
kern.mmxopt Toggles the mmx optimizations for the bcopy/copyin/copyout
routines
kern.vm.kmem.size
Sets the size of kernel memory (bytes). This overrides the
value determined when the kernel was compiled.
kern.maxswzone
Limits the amount of KVM to be used to hold swap meta
information, which directly governs the maximum amount of
swap the system can support. This value is specified in
bytes of KVA space and defaults to around 70MBytes. Care
should be taken to not reduce this value such that the
actual amount of configured swap exceeds 1/2 the kernel-
supported swap. The default 70MB allows the kernel to sup-
port a maximum of (approximately) 14GB of configured swap.
Only mess around with this parameter if you need to greatly
extend the KVM reservation for other resources such as the
buffer cache or NMBCLUSTERS. Modifies VM_SWZONE_SIZE_MAX.
kern.maxbcache
Limits the amount of KVM reserved for use by the buffer
cache, specified in bytes. The default maximum is 200MB.
This parameter is used to prevent the buffer cache from
eating too much KVM in large-memory machine configurations.
Only mess around with this parameter if you need to greatly
extend the KVM reservation for other resources such as the
swap zone or NMBCLUSTERS. Note that the NBUF parameter
will override this limit. Modifies VM_BCACHE_SIZE_MAX.
machdep.disable_mtrrs
Disable the use of i686 MTRRs (x86 only).
net.inet.tcp.tcbhashsize
Overrides the compile-time set value of TCBHASHSIZE or the
preset default of 512. Must be a power of 2.
vfs.root.mountfrom
A semicolon separated list of partitions to try as the ker-
nel root file system. Device format is file system type
and partition, separated by colon. Used with boot-only
partition, which is typically mounted on root file system
as /boot.
- One device example: "hammer:da8s1a"
- Several devices example: "ufs:da0s1a;hammer:ad1s1d"
Each device in the list will be tried in the order speci-
fied until the mount succeeds. If all fail, the mountroot>
prompt is displayed for manual entry.
You may not specify devtab labels here but you can specify
paths available to devfs such as "ham-
mer:serno/L41JYE0G.s1d".
BUILTIN PARSER
When a builtin command is executed, the rest of the line is taken by it
as arguments, and it is processed by a special parser which is not used
for regular Forth commands.
This special parser applies the following rules to the parsed text:
1. All backslash characters are preprocessed.
* \b , \f , \r , \n and \t are processed as in C.
* \s is converted to a space.
* \v is converted to ASCII 11.
* \z is just skipped. Useful for things like ``\0xf\z\0xf''.
* \0xN and \0xNN are replaced by the hex N or NN.
* \NNN is replaced by the octal NNN ASCII character.
* \" , \' and \$ will escape these characters, preventing them
from receiving special treatment in Step 2, described below.
* \\ will be replaced with a single \ .
* In any other occurrence, backslash will just be removed.
2. Every string between non-escaped quotes or double-quotes will be
treated as a single word for the purposes of the remaining steps.
3. Replace any $VARIABLE or ${VARIABLE} with the value of the environ-
ment variable VARIABLE.
4. Space-delimited arguments are passed to the called builtin command.
Spaces can also be escaped through the use of \\ .
An exception to this parsing rule exists, and is described in BUILTINS
AND FORTH.
BUILTINS AND FORTH
All builtin words are state-smart, immediate words. If interpreted, they
behave exactly as described previously. If they are compiled, though,
they extract their arguments from the stack instead of the command line.
If compiled, the builtin words expect to find, at execution time, the
following parameters on the stack:
addrN lenN ... addr2 len2 addr1 len1 N
where addrX lenX are strings which will compose the command line that
will be parsed into the builtin's arguments. Internally, these strings
are concatenated in from 1 to N, with a space put between each one.
If no arguments are passed, a 0 must be passed, even if the builtin
accepts no arguments.
While this behavior has benefits, it has its trade-offs. If the execu-
tion token of a builtin is acquired (through ' or [']), and then passed
to catch or execute, the builtin behavior will depend on the system state
at the time catch or execute is processed ! This is particularly annoying
for programs that want or need to handle exceptions. In this case, the
use of a proxy is recommended. For example:
: (boot) boot ;
FICL
FICL is a Forth interpreter written in C, in the form of a forth virtual
machine library that can be called by C functions and vice versa.
In loader, each line read interactively is then fed to FICL, which may
call loader back to execute the builtin words. The builtin include will
also feed FICL, one line at a time.
The words available to FICL can be classified into four groups. The ANS
Forth standard words, extra FICL words, extra DragonFly words, and the
builtin commands; the latter were already described. The ANS Forth stan-
dard words are listed in the STANDARDS section. The words falling in the
two other groups are described in the following subsections.
FICL EXTRA WORDS
.env
.ver
-roll
2constant
>name
body>
compare This is the STRING word set's compare.
compile-only
endif
forget-wid
parse-word
sliteral This is the STRING word set's sliteral.
wid-set-super
w@
w!
x.
empty
cell-
-rot
DRAGONFLY EXTRA WORDS
$ (--) Evaluates the remainder of the input buffer, after having
printed it first.
% (--) Evaluates the remainder of the input buffer under a catch
exception guard.
.# Works like . but without outputting a trailing space.
fclose (fd --)
Closes a file.
fkey (fd -- char)
Reads a single character from a file.
fload (fd --)
Processes a file fd.
fopen (addr len mode -- fd)
Opens a file. Returns a file descriptor, or -1 in case of
failure. The mode parameter selects whether the file is to be
opened for read access, write access, or both. The constants
O_RDONLY, O_WRONLY, and O_RDWR are defined in support.4th,
indicating read only, write only, and read-write access,
respectively.
fread (fd addr len -- len')
Tries to read len bytes from file fd into buffer addr. Returns
the actual number of bytes read, or -1 in case of error or end
of file.
heap? (-- cells)
Return the space remaining in the dictionary heap, in cells.
This is not related to the heap used by dynamic memory alloca-
tion words.
inb (port -- char)
Reads a byte from a port.
key (-- char)
Reads a single character from the console.
key? (-- flag)
Returns true if there is a character available to be read from
the console.
ms (u --)
Waits u microseconds.
outb (port char --)
Writes a byte to a port.
seconds (-- u)
Returns the number of seconds since midnight.
tib> (-- addr len)
Returns the remainder of the input buffer as a string on the
stack.
trace! (flag --)
Activates or deactivates tracing. Does not work with catch.
DRAGONFLY DEFINED ENVIRONMENTAL QUERIES
arch-i386
TRUE if the architecture is IA32.
DragonFly_version
DragonFly version at compile time.
loader_version
loader version.
SYSTEM DOCUMENTATION
FILES
/boot/loader loader itself.
/boot/boot.4th Additional FICL initialization.
/boot/boot.conf loader bootstrapping script. Deprecated.
/boot/defaults/loader.conf
/boot/loader.conf
/boot/loader.conf.local loader configuration files, as described in
loader.conf(5).
/boot/loader.rc loader bootstrapping script.
/boot/loader.help Loaded by help. Contains the help messages.
EXAMPLES
Boot in single user mode:
boot -s
Load kernel's user configuration file. Notice that a kernel must be
loaded before any other load command is attempted.
load kernel
load -t userconfig_script kernel.conf
Load the kernel, a splash screen, and then autoboot in five seconds.
load kernel
load splash_bmp
load -t splash_image_data chuckrulez.bmp
autoboot 5
Set the disk unit of the root device to 2, and then boot. This would be
needed in a system with two IDE disks, with the second IDE disk hardwired
to ad2 instead of ad1.
set root_disk_unit=2
boot kernel
ERRORS
The following values are thrown by loader:
100 Any type of error in the processing of a builtin.
-1 Abort executed.
-2 Abort" executed.
-56 Quit executed.
-256 Out of interpreting text.
-257 Need more text to succeed -- will finish on next run.
-258 Bye executed.
-259 Unspecified error.
SEE ALSO
libstand(3), loader.conf(5), tuning(7), boot(8), btxld(8), sysctl(8)
STANDARDS
For the purposes of ANS Forth compliance, loader is an ANS Forth System
with Environmental Restrictions, Providing .(, :noname, ?do, parse, pick,
roll, refill, to, value, \, false, true, <>, 0<>, compile, , erase, nip,
tuck and marker from the Core Extensions word set, Providing the Excep-
tion Extensions word set, Providing the Locals Extensions word set, Pro-
viding the Memory-Allocation Extensions word set, Providing .s, bye, for-
get, see, words, [if], [else] and [then] from the Programming-Tools
extension word set, Providing the Search-Order extensions word set.
HISTORY
The loader first appeared in FreeBSD 3.1.
AUTHORS
The loader was written by Michael Smith <msmith@FreeBSD.org>.
FICL was written by John Sadler <john_sadler@alum.mit.edu>.
BUGS
The expect and accept words will read from the input buffer instead of
the console. The latter will be fixed, but the former will not.
DragonFly 2.7 July 4, 2010 DragonFly 2.7