install-mbr - install a Master Boot Record manager
installs and configures a Master Boot Record manager on a
device. The behaviour of the boot manager is determined by the options given
on the command line. <target
> is the path specifying the device
(or file) that the boot manager should be installed onto.
When the MBR is first loaded it waits for a configurable length of time (1
second by default), monitoring the keyboard for key presses. The types of key
which cause the MBR to be interrupted can be configured through the -i option
If the MBR is interrupted, it will display its prompt. Otherwise it will load
the first sector of the default partition and execute it. If a disk error
occurs or the boot signature is missing, the prompt will be displayed.
The boot prompt looks something like this:
This is the list of valid keys which may be pressed followed by a colon. Numeric
keys indicate primary partitions on the disk beginning with partition 1 and
'F' indicates the floppy disk. Extended partitions cannot be booted. The 'A'
means that 'advanced' mode may be entered, in which case any partition may be
booted. The only other valid key which may be pressed is RETURN, which
continues booting with the default partition.
The prompt for advanced mode looks like this and works just the same as the
The list of valid partitions and the default partition can be configured through
the -e and -p options to install-mbr.
These options change the way the installation program operates.
- --force, -f
- This option currently overrides a check to make sure the
specified target is valid.
<path>, -I <path>
This option may be used to install code other
than that which is built in to install-mbr. It is mainly useful for
testing, but may be used to install older versions of the MBR.
- --keep, -k
- This option instructs the installer to modify the
parameters stored in the MBR without updating the code.
- --list, -l
- This option may be used to view the parameters being
installed in the MBR. It implies the --no-act and --keep
flags unless an option other than --offset, --verbose or
--list is given. This allows the contents of the MBR to be
- --no-act, -n
- This option ensures that the target is not modified, as it
is opened in read-only mode.
<offset>, -o <offset>
This option may be used to install the MBR
somewhere other than the start of the target. The offset specifies the number
of bytes from the start of the target at which the MBR should be installed.
For example, an offset of 128 may be used for DOSEMU disk images.
This option specifies the status of the Y2K
bug fix parameter. When set, an alternative MBR is installed that fixes a Y2K
bug in some BIOSes that causes them to always boot up the machine with the
year ranging from 94 to 99. This MBR stores the current month and year and
sets the year based on this when the computer is booted. It also increases the
year automatically when the current month is lower than the month of the last
boot. The initial year and month are set based on the current system time
converted to UTC or the local time as specified by the argument. If the
argument is not specified, the default is read from /etc/default/rcS. Due to
space limitations, the alternative version of the MBR does not display the
word MBR as it boots. If the argument is =off or - the Y2K bug
fix is disabled. WARNING: The Y2K bug fix will work fine until you want
to set the date backwards. When you do want to do this, you will need to
reinstall the MBR. You cannot just set the date in the BIOS (since the whole
point of this option is that the year provided by the BIOS is ignored).
<path>, -P <path>
This option may be used to copy parameters
from somewhere other than the target. The path specifies a location where a
version of this MBR has been installed and parameters are read from there. It
could be used to copy parameters from one disk to another disk.
- --reset, -r
- This option is used to reset the boot parameters to the
state found in the code being installed (or code which would be installed
if --keep were not specified).
<path>, -T <path>
The master boot record currently uses the
partition table in the sector which contains it to locate boot sectors (This
behaviour may change with future versions of the MBR, in which case the option
may be withdrawn). The --table option is used to copy a partition table
from another location to the target location. Any data stored on the target
disk may be lost (as the partition table is overwritten), so this option
should be used with extreme caution. As the partition table is copied, any
changes made to the original partition table will not be noticed. This option
is only provided to make installation to floppy easy.
- --verbose, -v
- When invoked with this option, install-mbr will
display some information about what it is doing.
- --version, -V
- This option will cause install-mbr to display it's
version number and exit.
- --help, -h
- This option will cause install-mbr to display a help
message and exit.
These options change the parameters stored within the Master Boot Record.
<drive>, -d <drive>
This option instructs the MBR to boot a drive
other than the first hard disk. It may be specified in decimal or hexadecimal
if prefixed with 0x. Hard disks are numbered starting from 128 (0x80).
<option>, -e <option>
This option sets the list of boot sectors
which may be loaded (or advanced mode). A boot sector may be loaded from one
of the first 4 partitions of the disk, or from the first floppy drive. Use
> to add a boot sector to the list or
> to remove a boot sector from the list.
Use --enable =
> to set the list to
> may contain:
- 1, 2, 3, 4
- The specified partition number.
- The first floppy disk.
- Advanced mode (not a boot sector).
<mode>, -i <mode>
This option sets the list of events which will
cause the MBR to display it's prompt. Use -i +<event> to add an event to
the list or -i -<event> to remove an event from the list. Values of
- A shift or control key is pressed.
- A non shift-like key is pressed
- The prompt is always displayed.
- Never display the prompt (unless an error occurs).
<partn>, --partition <partn>
This specifies the default boot sector to
load. Valid values of <partn
- 1, 2, 3, 4
- The specified partition number.
- The first floppy disk.
- The partition marked with the bootable flag in the
<timeout>, --timeout <timeout>
This option changes the time which the MBR
waits for before booting the default partition to the value specified in 1/18
seconds (approx). The maximum timeout that can be specified is 65534 which is
about an hour.
install-mbr /dev/fd0 -T /dev/hda
Install the default MBR image on /dev/fd0
, taking the partition table
install-mbr -kr /dev/hda
Reset the parameters on /dev/hda
without installing any new code.
install-mbr -I my-mbr -T /dev/hda -P my-parameters /dev/fd0
Install to /dev/fd0
, taking code from my-mbr
, partition table from
and parameters from my-parameters.
install-mbr -l -o 128 hdimage
List the parameters stored at offset 128 in hdimage
(may be a DOSEMU
install-mbr -d 0x81 -T /dev/hdb /dev/fd0
Install on /dev/fd0
to boot from BIOS drive 129 (0x81) with partition
table copied from /dev/hdb
install-mbr -e 13 /dev/hda
install-mbr -e 2 -e =13 /dev/hda
install-mbr -e1 -e3 /dev/hda
Enable booting from partitions 1 and 3 on /dev/hda
. Other locations are
install-mbr -e +f-a -i sk /dev/hda
Enabled booting from the floppy drive, and disable advanced mode. Display the
prompt if any shift, control or non shift-like key is pressed. Other settings
- Cannot handle MBR version n (backwards compatible to
This error means that the version of MBR which is being installed is not
known about by this installer. Such files cannot have their parameters
read or written. If such a newer version is installed, it can be
downgraded by specifying the --reset option (without specifying
The operation of --list
may be confusing.
was written for the Debian project by Neil Turton