monitor(8)
NAME
monitor, edparams - load and start Minix, modify boot parameters
SYNOPSIS
/boot
edparams device [command ...]
boot.com virdisk [command ...]
DESCRIPTION
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 interface to configure Minix and to boot other
operating systems.
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 main, which by default starts a simple menu.
The environment can be manipulated at boot time from the monitor prompt,
but may also be edited using edparams on a given device. 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.
The DOS version of the monitor, usually named boot.com under DOS, boots
Minix from a "DOS virtual disk". Boot.com is a simple COM program that
interprets a 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 boot command, it can only load Minix. The monitor grabs as much
free memory as it can for Minix to work in, as the memory variable shows.
Further details on how to run Minix under DOS, Windows 95, or even
Windows NT are written down in dosminix(8).
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:
name = [device] value
Set environment variable.
Changes the value of name to value. The optional word device marks
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:
rootdev
This is the device used as your root device. It is by default
set to ram, which means that the device specified by
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 ramsize.
ramimagedev
Describes the device to use to initialize the RAM disk if
rootdev is set to ram. It's by default set to bootdev, a
special name for the device the monitor booted from.
ramsize
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
ramsize if possible.
processor
Set by default to 86, 186, 286, 386, 486, ... depending on the
hardware you have. You can set it to a smaller value to test
your kernel in a more limited environment.
bus
The type of system bus, either xt, at or mca. This answers
basic questions like: "How many interrupt controllers and how
to initialize?" Or: "Does the keyboard have LEDs?"
memory
List of memory free for use by Minix. It is a comma separated
list of base:size pairs denoting the byte offsets and sizes of
free memory in hexadecimal. 800:925E0,100000:F00000 is a
typical example of about 585K starting at 2K, and 15M starting
at 1M. (The first 2K are BIOS parameters and the 53K under the
640K boundary is the monitor itself.) The very last number you
can play with if you know what you are doing. Either increase
it if the monitor has it wrong, or decrease it to test if Minix
still runs with less memory then normal.
video
Describes capabilities of the VDU: mda, cga, ega or vga.
chrome
Either color or mono.
c0
By default at (AT compatibles), bios (XT or PS/2), or dosfile
(running under DOS). The c0 variable binds a driver to the
first controller, i.e. the /dev/c0* devices. The monitor sets
c0 to a suitable default, so that most machines can find their
disk.
console
If set to a hexadecimal value it makes the monitor set the BIOS
video mode to this value when Minix is started. This allows
the use of video modes with more rows or colums than the
standard 80x25 mode. You can use any text mode in the 00-FF
range, and VESA extended modes in the 100-FFF range. Most text
modes use a 9x16 font with 400 scanlines on screen, so you see
400/16 = 25 lines. The text mode can be modified by adding
special flags to the console setting. Add 2000 to switch to
480 scan lines, adding 20% more lines to the screen. Add 4000
to select a 9x14 font, so 28 or 34 lines are shown. Add 8000
instead to select an 8x8 font showing 50 or 60 lines. Each
setting has drawbacks. Using 480 scanlines implies a 60 Hz
refresh, so the screen may flicker. The 8x8 font looks
squashed. More letters on screen require more memory, so there
is less for virtual consoles. Interesting modes to try are
4003 (80x28), 2003 (80x30), 6003 (80x34), 8003 (80x50), A003
(80x60), 109 (132x25), 10A (132x43), 10B (132x50), 10C
(132x60). The 109 VESA mode is often available, and can be
modified like mode 3. Use mode 7 instead of 3 for monochrome.
Which modes and flags work can only be found out by experiment.
More parameters may follow the mode number that are of interest
to the console driver, see boot(8).
dosfile-d0
Set by the DOS version of the monitor to the name of the
virtual disk, i.e. the virdisk argument as shown above. The
"dosfile" driver will use this as the name of the file to use
as a disk.
Two variables are only used by the monitor, even though they are
passed to the kernel too:
image
The name of the file containing the kernel image, by default
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 /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:
A '/' or '_' is changed to a space.
The first letter is changed from lowercase to uppercase.
An 'r' if followed by a digit changes to " revision ".
label
If set then only processes marked with this label or without a
label are loaded from the image.
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.
name() command
Define function.
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.
ram() { rootdev=ram; boot }
will allow you to run Minix with the root device on RAM for a
change, if you normally use a real device as root. There are three
predefined functions, leader, with default value an echo command
that shows the monitor's startup banner, main, with default value
menu, and trailer, with default value a command that clears the
screen. The monitor executes leader;main at startup to show the
banner message and a menu. The trailer function is executed just
before Minix is started. These three functions can be redefined as
you please.
name(key) command
Define kernel selecting function.
The menu command uses functions like these to add menu entries to
select a different kernel from a boot disk. Installboot -boot
produces these functions when the images are labeled. The label AT
would give:
AT(a) {label=AT;image=42:626;echo AT kernel selected;menu}
With the menu option:
a Select AT kernel
Typing a will then execute the AT function above.
name(key,text) command
User defined menu option.
This variant may be used to make any menu entry you like:
dos(d,Boot MS-DOS) boot d0p0
Text may be anything, even parentheses if they match.
name
Call function.
If name is a user defined function then its value is expanded and
executed in place of 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 chmem(1) to increase it's heap.
boot [-opts]
boot device
Boot Minix or another O.S.
Without an argument, boot will load and execute the Minix image
named by the image variable. With options the variable bootopts is
first set to -opts before Minix is started, and unset when Minix
returns. With a device argument, boot loads the boot sector of
device into memory and jumps to it, starting another operating
system. You would normally use partitions on the first hard disk
for this command (d0p[0-3]), using d0 will also work (choosing the
active partition). One can also boot devices on the second hard
disk (d1, d1p[0-3]) if the bootstrap writer did not hardwire the
disk number to disk 0.
Some Operating Systems can only be booted from the active partition,
if you use a '*', e.g. boot *d0p2, then partition 2 is first made
active. You'll then need to use
installboot -m /dev/c0d0 /usr/mdec/jumpboot keys
with keys chosen so that Minix is booted at startup. (See
installboot(8).)
ctty n
Copies output to and takes input from serial line n (0-3) at 9600
baud, 8 bits, no parity. This allows you to control a Minix system
remotely through an RS-232 connection.
delay [msec]
Delay (500 msec default).
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 delay to make the monitor pause for a specified
number of milliseconds.
echo word ...
Print these words.
Used to display messages, like the startup banner. Echo normally
prints the words with spaces in between and a newline at the end.
Echo understands special '\' escape sequences as follows:
\ (At the end) Don't print a newline.
\n Print a newline.
\v Print the monitor's version numbers.
\c Clear the screen.
\w Wait until a RETURN is typed
\\ Print a backslash.
ls [directory]
List contents of a directory.
Useful when looking for kernel images.
menu
Menu driven startup.
This command allows you to execute functions defined with a key. If
no menu functions have been defined then menu will use this one
hidden built-in function:
*(=,Start Minix) boot
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.
Menu entries are shown in the same order as set shows them. If you
don't like the order then you have to unset the functions and retype
them in the proper order.
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.
save
Save environment.
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.
set
Show environment.
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.
trap msec function
Schedule function.
Schedules a function to be executed after msec milliseconds. Only
the monitor mode cannot be interrupted, a scheduled trap is killed
when the prompt is printed. Example:
main() {trap 10000 boot; menu}
This gives you 10 seconds to choose a menu option before Minix is
booted.
unset name ...
Unset environment variables.
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.
exit
Exit the monitor.
Reboot the machine, exit to Minix or exit to DOS as appropriate.
off
Turn the PC off.
If the PC supports power management then turn it off, otherwise
print some error messages and do nothing.
{ command; ... }
Bundle commands.
Treat a number of commands as a single command. Used for function
definitions when a function body must contain more than one command.
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 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', 'c0d1p0', 'c1d0p2s0', and even
the obsolete 'hd2a' to what it itself thinks the numbers should be.
The special name bootdev is translated to the name of the device booted
from, like 'fd0', or 'c0d0p1s0', and then searched for in /dev. Bootdev
can only be translated to a device for the first controller, and only if
the disks on that controller are numbered without "gaps". (The master
device on the second IDE channel is always d2 on Minix. The BIOS will
call it disk 0, 1, or 2 depending on the number of disks on the first IDE
channel.)
Controller numbers are meaningless to the BIOS, so everything is assumed
to be attached to controller 0. You can omit c0 for device names, and it
is best to always omit c0 for the boot command, and to always use the
full name for variables passed to Minix.
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:
0x0001 Call kernel in 386 mode.
0x0002 Do not make space for the bss areas of processes other than the
kernel.
0x0004 Use the stack size set by chmem(1).
0x0008 Load MM, FS, etc. into extended memory.
0x0010 No need to patch process sizes into the kernel.
0x0020 The kernel can return to the monitor on halt or reboot.
0x0040 Offer generic BIOS support instead of just INT 13 (disk I/O).
0x0080 Pass memory lists for free and used memory (processes).
0x0100 Kernel returns monitor code on shutdown in boot parameters
array.
SEE ALSO
controller(4), installboot(8), usage(8), boot(8), dosminix(8).
BUGS
The delay command will hang forever on the original IBM PC (not the XT!).
Not that it matters, as everything takes forever on that box.
By redefining leader one can easily hide the identity of this program.
ACKNOWLEDGMENTS
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 Sun ROM boot monitor, which is also true.
AUTHOR
Kees J. Bot (kjb@cs.vu.nl)