installboot(8)
NAME
installboot - make a device bootable
SYNOPSIS
installboot -i(mage) image [label:]kernel mm fs ... init
installboot -(e)x(tract) image
installboot -d(evice) device bootblock boot [[label:]image ...]
installboot -b(oot) device bootblock boot [label:]image ...
installboot -m(aster) [fix] device masterboot
DESCRIPTION
Installboot may be used to make a device bootable by constructing a
kernel image and installing bootstrap code into the boot block of a Minix
file system. To understand how this can be done one first has to know
what happens when a PC is booted.
When the power is turned on the typical PC will try to read the first
sector from the first floppy disk or from the first hard disk into memory
and execute it. The code obtained from the hard disk (from the so-called
master boot sector) will immediately replace itself by the code found in
the first sector of the active partition. Thus the PC is now executing
the bootstrap code found in the first sector of /dev/fd0, /dev/hd1,
/dev/hd2, /dev/hd3, or /dev/hd4. The bootstrap will locate the operating
system on the device it itself was loaded from, load it, and execute it.
To make a Minix file system /dev/fd0 mounted on /mnt bootable, enter the
following:
cp /usr/mdec/boot /mnt/boot
installboot -i /mnt/minix kernel mm fs init
installboot -d /dev/fd0 /usr/mdec/bootblock boot
The "boot" program in the example is named the "boot monitor". It is
loaded by the bootblock code placed in the boot sector of /dev/fd0 and it
will take care of loading the kernel image "minix" from the root
directory of the file system. See monitor(8) for a description of the
boot monitor. Note that boot is a name in the file system on /dev/fd0 in
this example, the same file as /mnt/boot. Making /mnt/minix is normally
not necessary, there is usually a kernel image in the tools directory.
OPTIONS
-i(mage) image [label:]kernel mm fs ... init
The -image option (or the -i shorthand) combines the executable
files needed to run Minix in one file. Only the names and a few
zero bytes are inserted into the image. The name is for
identification and the zeros are used to pad separate pieces to
sector boundaries for fast loading.
An executable may be prefixed by a label. The monitor may be
instructed to load processes by label. So more than one kernel
process may be included in the image, each with a different
winchester driver for instance. So if you have compiled two
different kernels with an AT or XT driver then
installboot -i image AT:at_kernel XT:xt_kernel mm fs init
will make an image with two different labeled kernels and one
unlabeled set of the other binaries.
-(e)x(tract) image
Extract the binaries from image under the names stored in the image.
(The name includes the optional label.)
-d(evice) device bootblock boot [[label:]image ...]
Installs bootblock in the boot sector of device together with the
disk addresses to boot. These disk addresses are needed to load
boot from the file system at boot time. The argument boot is first
searched in the file system on device. If it is not found then it
is read as a normal file and added at the end of the file system.
The file system should be smaller than the device it is on to allow
this. Any extra images are also added to the end as described under
-boot. (Make sure you understand all this.)
The device need not be mounted when installboot is run, nor does it
matter if it is.
Installboot needs to be run again if boot is rewritten, because it
will then occupy a new place on the disk.
Old boot parameters are kept if there are no images added.
-b(oot) device bootblock boot [label:]image ...
This option fills a blank floppy in device with boot code and kernel
images. This "boot disk" does not have a root file system, only the
boot monitor and Minix kernels. The boot parameters sector is
filled with code that enables menu options for selecting an image.
After loading an image, the monitor will ask you to insert a root
file system diskette before starting Minix.
The labels used on the images should match those on the executables
used inside the image. You can put a comma separated list of labels
on an image for each label used within the image. For the image
created earlier one would create a boot floppy like this:
installboot -b /dev/fd0 bootblock boot AT,XT:image
If a label-list is omitted on an image, then that image will be
selected by default. (Like in the normal one image, no labels
case.)
Note that -device and -boot together allow you to make a boot floppy
with or without a root file system. With the boot code in the file
system, attached to the end of it, or after the boot block. And
with one or more kernel images in the file system or at the end of
the device. Somewhat confusing.
-m(aster) [fix] device masterboot
This option installs the masterboot program into the boot sector of
the given device. If another device is given instead of masterboot
then its bootstrap code is copied to device. The master bootstrap
on a hard disk boots the active partition on that disk at boot time.
The MS-DOS fdisk command normally puts a master bootstrap on the
hard disk. Minix has two bootstraps that can be used as a master
bootstrap. A fairly normal one named masterboot that works as
follows:
If the ALT key is held down while booting then '/dev/hd?'
appears and you are expected to type a number key (0 - 9) to
select the device to boot.
If fix (a small number) is given then the bootstrap is locked
into booting the /dev/hdfix disk or primary partition. This is
needed if 'boot *hdN' is used from the monitor to boot an O.S.
that needs the active flag set.
If installed on a Minix floppy then it will try to boot the
next floppy or the first hard disk. Ideal for floppies with
just data on it, they will no longer obstruct the boot process
if left in the drive. Also a very useful trick to boot from
floppy drive 1.
If installed on a hard disk then the active partition is
selected and booted as usual, unless none of the partitions is
marked active, then it will boot the next disk. The latter is
useful if you want to boot an operating system from the second
disk by default.
The second bootstrap is named extboot. It has only one function, to
boot the logical partition named by fix. Fix is not optional for
extboot and must be a number-letter pair, like 2c for /dev/hd2c.
Extboot or masterboot with a fix key need not be installed in the
hard disk master bootstrap per se if you don't want to mess with the
DOS master bootstrap, or if you want keep the active flag
functioning. An extended partition or a non-root Minix partition
are better candidates. It seems logical to put extboot in the
extended partition boot block.
A backup copy of the current master bootstrap (including the
partition table) can be made with:
dd if=device of=backup-file count=1
A simple 'cat backup-file > device' will put it back. You can also
use fdisk /mbr under MS-DOS 5.0 (or newer) to restore the master
bootstrap.
FILES
/usr/mdec/bootblock Minix bootstrap for the Minix root device. To
be placed in the boot sector.
/usr/mdec/boot Minix Boot Monitor. Can usually be found in the
root directory of a bootable device.
/usr/mdec/masterboot Master bootstrap. Can be placed in the first
sector of a disk to select the active partition.
In a Minix primary partition it selects the
active subpartition.
/usr/mdec/extboot Extended partition bootstrap.
SEE ALSO
part(8), monitor(8).
DIAGNOSTICS
Boot doesn't fit on device
If there is no space on the device to add the boot code. This
usually means that there is no boot code in the file system you use
installboot -device on.
Image doesn't fit on device
If the device is too small for all the images you try to put on it.
BUGS
It has four more options than the SunOS installboot program it is modeled
after.
The bootblock code has been crunched to such ugliness that you can use it
to scare little kids out of your garden.
AUTHOR
Kees J. Bot (kjb@cs.vu.nl)