monitor.8

操作系统设计与实现源码

.TH MONITOR 8
.SH NAME
monitor, edparams \- load and start Minix, modify boot parameters
.SH SYNOPSIS
.B edparams
.I device
.RB [ command " ...]"
.br
.B boot.com
.I virdisk
.SH DESCRIPTION
.de SP
.if t .sp 0.4
.if n .sp
..
This text describes the Boot Monitor, a boot time interactive program designed
not only to load and start Minix, its most important task, but to also
provide an easy to use interface to configure Minix and to boot other
operating systems.
.PP
The monitor is controlled with an environment that is modeled after the
Bourne shell.  This environment is filled at startup with default values
that depend on the machine the monitor is running on and the environment
settings saved into the boot parameters sector (the second sector on a
device).  When the environment is loaded, the monitor executes the function
named
.BR main ,
which by default starts a simple menu.
.PP
The environment can be manipulated at boot time from the monitor prompt,
but may also be edited using
.B edparams
on a given device.
.B Edparams
simulates the monitor as much as it can, echoing commands it can't execute
between brackets.  It can also be used in Makefiles and scripts by giving
it commands as arguments.
.PP
The MS-DOS version of the monitor, usually named
.B boot.com
under DOS, boots Minix from a "DOS virtual disk".  (See below.)
.SH COMMANDS
The monitor is best described by the commands you can type to the '>'
prompt.  This is known as the "monitor mode".  You can enter this mode by
hitting the Escape key.  These are the monitor commands:
.PP
\fIname\fP = [\fBdevice\fP] \fIvalue\fP
.SP
.RS
Set environment variable.
.br
Changes the value of
.I name
to
.IR value .
The optional word
.B device
marks
.I name
as being subject to device translation.  (See the section on devices.)  These
(name, value) pairs are passed to the kernel who uses them to configure
itself.  These variables are passed by default:
.SP
.B rootdev
.RS
This is the device used as your root device.  It is by default set to
.BR ram,
which means that the device specified by
.B ramimagedev
will be loaded into the RAM disk and used as root.  If you change this
variable then a physical device will be used as root, and the RAM disk will
be uninitialized and have the size specified by
.BR ramsize .
.RE
.SP
.B ramimagedev
.RS
Describes the device to use to initialize the RAM disk if
.B rootdev
is set to
.BR ram .
It's by default set to
.BR bootdev ,
a special name for the device the monitor booted from.
.RE
.SP
.B ramsize
.RS
The size of the RAM disk.  If the RAM disk is used for the root file system
then the root file system is stretched out to
.B ramsize
if possible.
.RE
.SP
.B processor
.RS
Set by default to
.BR 86 ,
.BR 186 ,
.BR 286 ,
.BR 386 ,
.BR 486 ", ..."
depending on the hardware you have.  You can set it to a smaller value to
test your kernel in a more limited environment.
.RE
.SP
.B bus
.RS
The type of system bus, either
.BR xt ,
.BR at
or
.BR mca .
This answers basic questions like: "How many interrupt controllers and how
to initialize?"  Or: "Does the keyboard have LEDs?"
.RE
.SP
.B memsize
.RS
Kilobytes of conventional memory.  This is the amount of RAM within the
first megabyte.
.RE
.SP
.B emssize
.RS
Kilobytes of extended memory.
.RE
.SP
.B video
.RS
Describes capabilities of the VDU:
.BR mda ,
.BR cga ,
.B ega
or
.BR vga .
.RE
.SP
.B chrome
.RS
Either
.B color
or
.BR mono .
.RE
.SP
.B console
.RS
If set to a hexadecimal value makes the monitor set the BIOS video mode to
this value.  This allows the use of video modes with more rows or colums
than the standard 80x25 mode.  The kernel must of course be able to handle
a nonstandard mode.  More parameters may follow the mode number.
.B Warning:
Not all monitors can handle all of the modes, some may generate frequencies
that can damage your monitor.  Read the manual of card and monitor for
details.
.RE
.SP
Two variables are only used by the monitor, even though they are passed to the
kernel too:
.SP
.B image
.RS
The name of the file containing the kernel image, by default
.BR minix .
If it refers to a directory however then the newest file inside the
directory is chosen to be the kernel image.  The names inside
.B /minix/
are best set to the Minix version you are using, which looks good when the
monitor prints its name.  Rules for pretty printing image names:
.RS
.SP
A '/' or '_' is changed to a space.
.SP
The first letter is changed from lowercase to uppercase.
.SP
An 'r' if followed by a digit changes to " revision ".
.RE
.RE
.SP
.B label
.RS
If set then only processes marked with this label or without a label are
loaded from the image.
.RE
.SP
.B Installboot \-boot
will create functions to select images and labels.  These functions will set
label and image and echo what you selected.  The two numbers separated by a
colon used as an image name tell the starting sector and sector count of the
image on disk.
.RE
.SP
\fIname\fP() { ... }
.RS
Define function.
.br
Functions may be used to bundle a set of commands, so that you can easily
boot Minix with a different set of parameters then normal.  E.g.
.SP
.RS
ram() { rootdev=ram; boot }
.RE
.SP
will allow you to run Minix with the root device on RAM for a change, if
you normally use a real device as root.  The only pre-set function is
.B main
with default value
.BR menu ,
which is the default command executed by the monitor.  You can use newlines
after the ')' token, the monitor will then use a '+' prompt and ask for the
rest.
.RE
.SP
\fIname\fP(\fIkey\fP) { ... }
.RS
Define kernel selecting function.
.br
The menu command uses functions like these to add menu entries to select
a different kernel from a boot disk.
.B Installboot \-boot
produces these functions when the images are labeled.  The label
.B AT
would give:
.SP
.RS
AT(a) {label=AT;image=42:626;echo AT kernel selected;menu}
.RE
.SP
With the menu option:
.SP
.RS
a	Select AT kernel
.RE
.SP
Typing
.B a
will then execute the
.B AT
function above.
.RE
.SP
\fIname\fP(\fIkey\fP,\fItext\fP) { ... }
.RS
User defined menu option.
.br
This variant may be used to make any menu entry you like:
.SP
.RS
dos(d,Boot MS-DOS) { boot hd1 }
.RE
.SP
.I Text
may be anything, even parentheses if they match.
.RE
.SP
.I name
.RS
Call function.
.br
If
.I name
is a user defined function then its value is expanded and executed in place of
.IR name .
Try a recursive one like 'rec() {rec;xx}' one day.  You can see the monitor
run out of space with nice messages about using
.BR chmem (1)
to increase it's heap.
.RE
.SP
\fBboot\fP [\fB\-\fP\fIopts\fP]
.br
\fBboot\fP \fIdevice\fP
.RS
Boot Minix or another O.S.
.br
Without an argument,
.B boot
will load and execute the Minix image named by the
.B image
variable.  With options the variable
.B bootopts
is first set to
.BI \- opts
before Minix is started, and unset when Minix returns.  With a
.I device
argument,
.B boot
loads the boot sector of
.I device
into memory and jumps to it, starting another operating system.  You would
normally use partitions on the first hard disk for this command (hd[1\-4]),
using hd0 will also work (choosing the active partition).  One can also boot
devices on the second hard disk (hd[5\-9]) if the bootstrap writer did not
hardwire the disk number to disk 0.
.br
Some Operating Systems can only be booted from the active partition, if
you use a '*', e.g.
.BR "boot *hd3" ,
then partition 3 is first made active.  You'll then need to use
.B installboot \-master
with a fix key to forcefully boot the Minix partition at startup.
.RE
.SP
\fBdelay\fP [\fImsec\fP]
.RS
Delay (500 msec default).
.br
Fast booting speed was one of the objectives when this program was created,
so a hard disk boot usually takes only a fraction of a second.  If you need
some time (to hit Escape, or stare at the numbers) you can use
.B delay
to make the monitor pause for a specified amount of time.  To specify a delay
just before Minix is started, you can set the variable
.B delay
to a number of milliseconds.  Example:
.SP
.RS
main() {delay 250; delay=500; boot}
.RE
.SP
Look at this carefully, 'delay 250' means: "wait 1/4 sec now!",
while 'delay=500' means: "wait 1/2 sec after loading Minix".
.SP
If you use
.B delay=swap
then the monitor will wait until you have inserted a root diskette and typed
RETURN.
.RE
.SP
\fBecho\fP \fIword\fP ...
.RS
Print these words.
.br
Used to tell you that you just selected image X.
.RE
.SP
\fBls\fP [\fIdirectory\fP]
.RS
List contents of a directory.
.br
Useful when looking for kernel images.
.RE
.SP
.B menu
.RS
Menu driven startup.
.br
This command allows you to execute functions defined with a
.IR key .
If no menu functions have been defined then
.B menu
will use this one hidden built-in function:
.SP
.RS
*(=,Start Minix) { boot }
.SP
.RE
Kernel selecting functions only add new options to this set, but if you
define a two argument function yourself then the above one is no longer
shown, allowing you to customize the menu completely.  Your first
function definition should therefore be one that starts Minix.
.SP
Menu entries are shown in the same order as
.B set
shows them.  If you don't like the order then you have to unset the
functions and retype them in the proper order.
.SP
If you type a key then a scheduled trap is killed and the appropriate menu
function is executed.  If you need more time to choose then hit the
spacebar.  A key not on the menu also kills a trap, but does nothing more.
.RE
.SP
.B save
.RS
Save environment.
.br
This will save all the environment variables and functions with nondefault
values to the parameter sector (the second sector on the boot device), so
they are automatically set the next time you boot the monitor.
.RE
.SP
.B set
.RS
Show environment.
.br
Show the current values of the environment variables and functions.  Default
values are shown between parentheses to distinguish them from values that
were explicitly set.
.RE
.SP
\fBtrap\fP \fImsec\fP \fIcommand\fP
.RS
Schedule command.
.br
Schedules a command to be executed after
.I msec
milliseconds.  Only the monitor mode cannot be interrupted, a scheduled trap
is killed when the prompt is printed.  Example:
.SP
.RS
main() {trap 10000 boot; menu}
.RE
.SP
This gives you 10 seconds to choose a menu option before Minix is booted.
.RE
.SP
\fBunset\fP \fIname\fP ...
.RS
Unset environment variables.
.br
Removes the named variables and functions from the environment, and sets
special variables back to their default values.  This is also the only way
to remove the "device name translation" property from a variable.
.RE
.SP
\fBexit\fP
.RS
Exit the monitor
.br
Reboot the machine, exit to Minix or exit to DOS as appropriate.
.RE
.SH DEVICES
The Minix kernel can't do anything with device names, so they have to be
translated to device numbers before they are passed to the kernel.  This
number is found under the st_rdev field (see
.BR stat (2))
of the file on the boot file system.  The monitor will look for the device
file with the working directory set to '/dev'.  If it can't find the device
name then it will translate names like 'ram', 'fd1', 'hd6', 'hd3a', and 'sd2'
to what it itself thinks the numbers should be.
.PP
The special name
.B bootdev
is translated to the name of the device booted from, like 'fd0', or 'hd3', and
then searched for in /dev.
.B Bootdev
can't be translated to a device other then the fd or hd devices, so SCSI
devices for instance must be named explicitly.
.SH EXTENSIONS
A few extensions have been made to this program for kernel hackers.  They
may be triggered by setting bits in the flags word in the kernel startup
code (the mpx file.)  The flag bits are:
.TP 10
0x0001
Call kernel in 386 mode.
.TP
0x0002
Do not make space for the bss areas of processes other then the kernel.
.TP
0x0004
Use the stack size set by
.BR chmem (1).
.TP
0x0008
Load MM, FS, etc. into extended memory.
.TP
0x0010
No need to patch process sizes into the kernel.
.TP
0x0020
The kernel can return to the monitor on halt or reboot.
.SH "MS-DOS MONITOR"
Minix-vmd has a version of the monitor that runs under MS-DOS to boot
a "DOS virtual disk".  It is a simple COM program that interprets an MS-DOS
file as a disk, loads a Minix kernel from the active partition in the same
way as the BIOS based monitor, and executes it to start Minix.  All the
monitor commands function in the same way, except for the
.B boot
command, it can only load Minix.  The memory that MS-DOS has in use is copied
out of the way when Minix takes control, and is put back in place when Minix
exits.  This memory shuffling also happens when the BIOS disk driver makes
BIOS calls, slowing things to a crawl.  It is better to use a Minix driver.
The MS-DOS monitor does not work if there is a memory manager active that
runs in 386 protected mode, like EMM386.
.SH "SEE ALSO"
.BR chmem (1),
.BR stat (2),
.BR installboot (8),
.BR usage (8),
.BR boot (8).
.SH BUGS
The
.B delay
command will hang forever on the original IBM PC (not the XT!).  Not that it
matters, as everything takes forever on that box.
.PP
Reading the first sector to boot a floppy (e.g.
.BR "boot fd1" ),
is done using whatever floppy parameters boot currently has available.  This
will probably always work.
.PP
The two forms of
.B delay
are a crock.
.PP
The word
.B emssize
comes from EMS, that has to do with expanded memory, not extended memory.
.SH ACKNOWLEDGMENTS
Guy Helmer, for the floppy sensing code that somehow disappeared into the
boot block.
.PP
Earl Chew, for the inspiration his ShoeLace package provided, unless he wants
to file a "look and feel" suit against me, then I will say I modeled it after
the SunOS ROM boot monitor, which is also true.
.SH AUTHOR
Kees J. Bot ([e-mail])