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LILO - Generic Boot Loader for Linux ("LInux LOader") by Werner Almesberger

Version 21-4 (release) -- John Coffman

Minor changes suggested by Werner to show that this release is derived
from the source code to his version 21. Added VERSION_MAJOR and
VERSION_MINOR to replace VERSION. The file VERSION is replaced by

The first and second stage loaders have been modified so that ONLY
'lba32' will use EDD packet calls. 'linear' will now always ask the
BIOS for the disk geometry, and then use C:H:S addressing.

Version 22 (beta) -- John Coffman

This version was created to allow booting on disks larger than 8.4Gb using
the Enhanced BIOS call (int 0x13, AH=0x42) and the packet-call interface.
These calls are supported on post-1998 systems, and through software BIOS
extensions such as EZ-DRIVE(tm).

My primary objective in making these changes to LILO, is not to break any-
thing. Hence, the 32-bit direct addressing of sectors is supported by a
new keyword in the 'lilo.conf' file: "lba32". This keyword is mutually
exclusive with the keyword "linear". On the command line, these options
are invoked with the new "-L" switch, or the old "-l" switch, respectively.

Apologies to Werner Almesberger for not communicating these changes/addi-
tions to him directly; but I have not been able to contact him by e-mail
at the address he provided in the latest 'lilo.lsm' file. I do now want
versions of LILO to get out-of-step.

Disk sector addresses are conveyed from the Map Installer (lilo executable)
to the boot loaders, first- and second-stages through a 5 byte structure:

sector [1..63] plus 2 high bits of Cylinder
cylinder [0..1023] low eight bits in this byte
device [0..3] for floppies, [0x80..0x8F] for hard disks
head [0..254] no, the max is 254, not 255
count [1...] number of sectors to transfer

The first two bytes are normally loaded into the CX register, the second
bytes into the DX register, and the last byte into the AL register. This
the call used for the C:H:S addressing scheme of the original IBM-PC BIOS.
LILO checks that the 64Kb DMA boundary is never crossed by a call, and that
the count never exceeds the sector count of one track on the disk.

When 'linear' is specified, a 24-bit, 0 based addressing scheme is
The low 8 bits are in 'sector'; the middle 8 bits in 'cylinder'; and the
8 bits are in 'head'. To flag this as a 'linear' address, the 'device'
has bit 6 set (mask 0x40 or'ed in). The count field is a maximum of 128,
since anything greater would cross a 64Kb DMA boundary. It is up to the
loader code (second stage only), to check that no track boundary is

The situation is more complicated with 'lba32' addressing. It is flagged
bit 5 of the 'device' byte being set (mask 0x20 or'ed in). The 32-bit
is spread over the 'sector', 'cylinder', 'head', and 'count' fields, from
byte to high byte, respectively. Whenever this full 32-bit address is
specified explicitly, the actual sector count to transfer is implied to be
one (1), and this fact is flagged in the 'device' byte by setting bit 5
(mask 0x10 or'ed in). When a multi-sector transfer is called for, the high
8-bits of the address are NOT specified explicitly, but are assumed to be
the same as the previous transfer, the 'count' of sectors to transfer will
be in the range [2..127], and bit 5 (mask 0x10) of the 'device' byte will

The first-stage loader uses single sector transfers only, so it uses a
simplified disk read routine, always assumes a sector transfer count of 1,
and always assumes that the full 32-bit address of the sector is specified
when 'lba32' mode is detected in the 'device' byte. However, the second-
stage loader is capable of multi-sector transfers when map-compaction has
been used (-c switch, or 'compact' global option), so it uses the fully
capable read routine to load the -initrd- image, and the -kernel- image.

Both 'linear' and 'lba32' will use the Enhanced BIOS packet calls, if they
are available. Otherwise, the disk address is converted to C:H:S, using
disk geometry returned by (int 0x13, AH=8). If cylinder overflow occurs --
i.e., cylinder > 1023, then error code '9f' is issued.

The BIOS calls used to implement large disk booting conform to the Enhanced
Disk Drive Specification, version 3.0, rev 0.8, dated March 12, 1998. This
document is available on-line from Phoenix Technologies Ltd., at:

Known bugs:
The chain loader, 'os2_d.b', still will not boot OS2 4.0 from a
partition on my "D:" drive. Boot Manager can, and I am still working on
the problem.

Version 21

Important: The file INCOMPAT contains vital (in)compatibility information
for this release of LILO. Read it before proceeding.

Installing boot loaders is inherently dangerous. Be sure to have some means
to boot your system from a different media if you install LILO on your hard

There is also a LaTeX version of this document in the "doc" directory.
It is much nicer to read than pure ASCII.


Please read the file INCOMPAT for compatibility notes.

The installation procedure is described in the section "Normal first-time
installation". Please read "Booting basics" for the whole story.


If you want to install LILO on your hard disk and if you don't want
to use all its features, you can use the quick installation script.
Read QuickInst for details.

LILO is a versatile boot loader for Linux. It does not depend on a
specific file system, can boot Linux kernel images from floppy disks and
from hard disks and can even act as a "boot manager" for other operating

* PC/MS-DOS, DR DOS, OS/2, Windows 95, Windows NT, 386BSD, SCO UNIX,
Unixware, ...

One of up to sixteen different images can be selected at boot time. Various
parameters, such as the root device, can be set independently for each
kernel. LILO can even be used as the master boot record.

This document introduces the basics of disk organization and booting,
continues with an overview of common boot techniques and finally describes
installation and use of LILO in greater detail. The troubleshooting section
at the end describes diagnostic messages and contains suggestions for most
problems that have been observed in the past.

Please read at least the sections about installation and configuration if
you're already using an older version of LILO. This distribution is
accompanied by a file named INCOMPAT that describes further
incompatibilities to older versions.

For the impatient: there is a quick-installation script to create a simple
but quite usable installation. See section "Quick installation" for

But wait ... here are a few easy rules that will help you to avoid most
problems people experience with LILO:

- _Don't panic._ If something doesn't work, try to find out what is
wrong, try to verify your assumption and only then attempt to fix it.
- Read the documentation. Especially if what the system does doesn't
correspond to what you think it should do.
- Make sure you have an emergency boot disk, that you know how to use it,
and that it is always kept up to date.
- Run /sbin/lilo _whenever_ the kernel or any part of LILO, including its
configuration file, has changed. When in doubt, run it. You can't run
/sbin/lilo too many times.
- If performing a destructive upgrade and/or erasing your Linux
partitions, de-install LILO _before_ that if using it as the MBR.
- Don't trust setup scripts. Always verify the /etc/lilo.conf they create
before booting.
- If using a big disk, be prepared for inconveniences: you may have to
use the LINEAR option.

System overview

LILO is a collection of several programs and other files:

The map installer is the program you run under Linux to put all files
belonging to LILO at the appropriate places and to record information
about the location of data needed at boot time. This program normally
resides in /sbin/lilo. It has to be run to refresh that information
whenever any part of the system that LILO knows about changes, e.g.
after installing a new kernel.
Various files contain data LILO needs at boot time, e.g. the boot
loader. Those files normally reside in /boot. The most important files
are the boot loader (see below) and the map file (/boot/map), where the
map installer records the location of the kernel(s).* Another important
file is the configuration file, which is normally called /etc/lilo.conf
The boot loader is the part of LILO that is loaded by the BIOS and that
loads kernels or the boot sectors of other operating systems. It also
provides a simple command-line interface to interactively select the
item to boot and to add boot options.

* LILO does not know how to read a file system. Instead, the map
installer asks the kernel for the physical location of files (e.g. the
kernel image(s)) and records that information. This allows LILO to work
with most file systems that are supported by Linux.

LILO primarily accesses the following parts of the system:

The root file system partition is important for two reasons: first, LILO
sometimes has to tell the kernel where to look for it. Second, it is
frequently a convenient place for many other items LILO uses, such as
the boot sector, the /boot directory, and the kernels.
The boot sector contains the first part of LILO's boot loader. It loads
the much larger second-stage loader. Both loaders are typically stored
in the file /boot/boot.b
The kernel is loaded and started by the boot loader. Kernels typically
reside in the root directory or in /boot.

Note that many of the files LILO needs at boot time have to be accessible
with the BIOS. This creates certain restrictions, see section "BIOS


The following sections describe how PCs boot in general and what has to be
known when booting Linux and using LILO in particular.

Disk organization

When designing a boot concept, it is important to understand some of the
subtleties of how PCs typically organize disks. The most simple case are
floppy disks. They consist of a boot sector, some administrative data (FAT
or super block, etc.) and the data area. Because that administrative data
is irrelevant as far as booting is concerned, it is regarded as part of the
data area for simplicity.

|Boot sector| |
|-----------+ |
| |
| Data area |
| |
| |

The entire disk appears as one device (e.g. /dev/fd0) on Linux.

The MS-DOS boot sector has the following structure:

0x000 |Jump to the program code|
0x003 | |
| Disk parameters |
| |
0x02C/0x03E | |
| Program code |
| |
| |
0x1FE | Magic number (0xAA55) |

LILO uses a similar boot sector, but it does not contain the disk
parameters part. This is no problem for Minix, Ext2 or similar file
systems, because they don't look at the boot sector, but putting a LILO
boot sector on an MS-DOS file system would make it inaccessible for MS-DOS.

Hard disks are organized in a more complex way than floppy disks. They
contain several data areas called partitions. Up to four so-called primary
partitions can exist on an MS-DOS hard disk. If more partitions are needed,
one primary partition is used as an extended partition that contains
several logical partitions.

The first sector of each hard disk contains a partition table, and an
extended partition and _each_ logical partition contains a partition table

| Partition table /dev/hda |
| +------------------------------------------|
| | Partition 1 /dev/hda1 |
| | |
| |------------------------------------------|
| | Partition 2 /dev/hda2 |
| | |

The entire disk can be accessed as /dev/hda, /dev/hdb, /dev/sda, etc. The
primary partitions are /dev/hda1 ... /dev/hda4.

| Partition table /dev/hda |
| +------------------------------------------|
| | Partition 1 /dev/hda1 |
| | |
| |------------------------------------------|
| | Partition 2 /dev/hda2 |
| | |
| |------------------------------------------|
| | Extended partition /dev/hda3 |
| | +----------------------------------------|
| | | Extended partition table |
| | |----------------------------------------|
| | | Partition 3 /dev/hda5 |
| | | |
| | |----------------------------------------|
| | | Extended partition table |
| | |----------------------------------------|
| | | Partition 4 /dev/hda6 |
| | | |

This hard disk has two primary partitions and an extended partition that
contains two logical partitions. They are accessed as /dev/hda5 ...

Note that the partition tables of logical partitions are not accessible as
the first blocks of some devices, while the main partition table, all boot
sectors and the partition tables of extended partitions are.

Partition tables are stored in partition boot sectors. Normally, only the
partition boot sector of the entire disk is used as a boot sector. It is
also frequently called the master boot record (MBR). Its structure is as

0x000 | |
| Program code |
| |
| |
0x1BE | Partition table |
| |
0x1FE | Magic number (0xAA55) |

The LILO boot sector is designed to be usable as a partition boot sector.
(I.e. there is room for the partition table.) Therefore, the LILO boot
sector can be stored at the following locations:

- boot sector of a Linux floppy disk. (/dev/fd0, ...)
- MBR of the first hard disk. (/dev/hda, /dev/sda, ...)
- boot sector of a primary Linux file system partition on the first hard
disk. (/dev/hda1, ...)
- partition boot sector of an extended partition on the first hard disk.
(/dev/hda1, ...)*

* Most FDISK-type programs don't believe in booting from an extended
partition and refuse to activate it. LILO is accompanied by a simple
program (activate) that doesn't have this restriction. Linux fdisk also
supports activating extended partitions.

It _can't_ be stored at any of the following locations:

- boot sector of a non-Linux floppy disk or primary partition.
- a Linux swap partition.
- boot sector of a logical partition in an extended partition.*
- on the second hard disk. (Unless for backup installations, if the
current first disk will be removed or disabled, or if some other boot
loader is used, that is capable of loading boot sectors from other

* LILO can be forced to put the boot sector on such a partition by using
the -b option or the BOOT variable. However, only few programs that
operate as master boot records support booting from a logical

Although LILO tries to detect attempts to put its boot sector at an invalid
location, you should not rely on that.

Booting basics

When booting from a floppy disk, the first sector of the disk, the
so-called boot sector, is loaded. That boot sector contains a small program
that loads the respective operating system. MS-DOS boot sectors also
contain a data area, where disk and file system parameters (cluster size,
number of sectors, number of heads, etc.) are stored.

When booting from a hard disk, the very first sector of that disk, the
so-called master boot record (MBR) is loaded. This sector contains a loader
program and the partition table of the disk. The loader program usually
loads the boot sector, as if the system was booting from a floppy.

Note that there is no functional difference between the MBR and the boot
sector other than that the MBR contains the partition information but
doesn't contain any file system-specific information (e.g. MS-DOS disk

The first 446 (0x1BE) bytes of the MBR are used by the loader program. They
are followed by the partition table, with a length of 64 (0x40) bytes. The
last two bytes contain a magic number that is sometimes used to verify that
a given sector really is a boot sector.

There is a large number of possible boot configurations. The most common
ones are described in the following sections.

MS-DOS alone
- - - - - -

| Master Boot Record Boot sector Operating system |
| DOS-MBR ------------> MS-DOS ------> COMMAND.COM |

This is what usually happens when MS-DOS boots from a hard disk: the
DOS-MBR determines the active partition and loads the MS-DOS boot sector.
This boot sector loads MS-DOS and finally passes control to COMMAND.COM.
(This is greatly simplified.)

- - - -

| Master Boot Record Boot sector Operating system |
| DOS-MBR ------------> MS-DOS ------> COMMAND.COM |
| ---> LOADLIN ------> Linux |

A typical LOADLIN setup: everything happens like when booting MS-DOS, but
in CONFIG.SYS or AUTOEXEC.BAT, LOADLIN is invoked. Typically, a program
like BOOT.SYS is used to choose among configuration sections in CONFIG.SYS
and AUTOEXEC.BAT. This approach has the pleasant property that no boot
sectors have to be altered.

Please refer to the documentation accompanying the LOADLIN package for
installation instructions and further details.

LILO started by DOS-MBR
- - - - - - - - - - - -

| Master Boot Record Boot sector Operating system |
| DOS-MBR ------------> LILO --------> Linux |
| ---> other OS |

This is a "safe" LILO setup: LILO is booted by the DOS-MBR. No other boot
sectors have to be touched. If the other OS (or one of them, if there are
several other operating systems being used) should be booted without using
LILO, the other partition has to be marked "active" with fdisk or activate.


- install LILO with its boot sector on the Linux partition.
- use fdisk or activate to make that partition active.
- reboot.


- make a different partition active.
- install whatever should replace LILO and/or Linux.

Several alternate branches
- - - - - - - - - - - - -

| Master Boot Record Boot sector Operating system |
| DOS-MBR ------------> MS-DOS ------> COMMAND.COM |
| ---> LOADLIN ------> Linux |
| ---> LILO --------> Linux |
| ---> MS-DOS --- ... |

An extended form of the above setup: the MBR is not changed and both
branches can either boot Linux or MS-DOS. (LILO could also boot other
operating systems.)

LILO started by BOOTACTV*
- - - - - - - - - - - - -

* Other, possibly better known boot switchers, e.g. OS/2 BootManager
operate in a similar way. The installation procedures typically vary.

| Master Boot Record Boot sector Operating system |
| BOOTACTV -----------> LILO --------> Linux |
| ---> other OS |

Here, the MBR is replaced by BOOTACTV (or any other interactive boot
partition selector) and the choice between Linux and the other operating
system(s) can be made at boot time. This approach should be used if LILO
fails to boot the other operating system(s).*

* And the author would like to be notified if booting the other
operating system(s) doesn't work with LILO, but if it works with an
other boot partition selector.


- boot Linux.
- make a backup copy of your MBR on a floppy disk, e.g.
dd if=/dev/hda of=/fd/MBR bs=512 count=1
- install LILO with the boot sector on the Linux partition.
- install BOOTACTV as the MBR, e.g.
dd if=bootactv.bin of=/dev/hda bs=446 count=1
- reboot.


- boot Linux.
- restore the old MBR, e.g.
dd if=/MBR of=/dev/hda bs=446 count=1
or FDISK /MBR under MS-DOS.

If replacing the MBR appears undesirable and if a second Linux partition
exists (e.g. /usr, _not_ a swap partition), BOOTACTV can be merged with the
partition table and stored as the "boot sector" of that partition. Then,
the partition can be marked active to be booted by the DOS-MBR.


# dd if=/dev/hda of=/dev/hda3 bs=512 count=1
# dd if=bootactv.bin of=/dev/hda3 bs=446 count=1

_WARNING:_ Whenever the disk is re-partitioned, the merged boot sector on
that "spare" Linux partition has to be updated too.

LILO alone
- - - - -

| Master Boot Record Operating system |
| LILO ---------------> Linux |
| ---> other OS |

LILO can also take over the entire boot procedure. If installed as the MBR,
LILO is responsible for either booting Linux or any other OS. This approach
has the disadvantage, that the old MBR is overwritten and has to be
restored (either from a backup copy, with FDISK /MBR on recent versions of
MS-DOS or by overwriting it with something like BOOTACTV) if Linux should
ever be removed from the system.

You should verify that LILO is able to boot your other operating system(s)
before relying on this method.


- boot Linux.
- make a backup copy of your MBR on a floppy disk, e.g.
dd if=/dev/hda of=/fd/MBR bs=512 count=1
- install LILO with its boot sector as the MBR.
- reboot.


- boot Linux.
- restore the old MBR, e.g.
dd if=/fd/MBR of=/dev/hda bs=446 count=1

If you've installed LILO as the master boot record, you have to explicitly
specify the boot sector (configuration variable BOOT=...) when updating the
map. Otherwise, it will try to use the boot sector of your current root
partition, which will usually work, but it will probably leave your system

- - -

The following names have been used to describe boot sectors or parts of
operating systems:

"DOS-MBR" is the original MS-DOS MBR. It scans the partition table for a
partition that is marked "active" and loads the boot sector of that
partition. Programs like MS-DOS' FDISK, Linux fdisk or activate
(accompanies LILO) can change the active marker in the partition table.
"MS-DOS" denotes the MS-DOS boot sector that loads the other parts of
the system (IO.SYS, etc.).
"COMMAND.COM" is the standard command interpreter of MS-DOS.
"LOADLIN" is a program that loads a Linux kernel image from an MS-DOS
partition into memory and executes it. It is usually invoked from
CONFIG.SYS and is used in combination with a CONFIG.SYS configuration
switcher, like BOOT.SYS.*
"LILO" can either load a Linux kernel or the boot sector of any other
operating system. It has a first stage boot sector that loads the
remaining parts of LILO from various locations.**
"BOOTACTV" permits interactive selection of the partition from which the
boot sector should be read. If no key is pressed within a given
interval, the partition marked active is booted. BOOTACTV is included
in the pfdisk package. There are also several similar programs, like
PBOOT and OS-BS.***

* LOADLIN is available for anonymous FTP from
BOOT.SYS is available for anonymous FTP from

** LILO can be found in

*** pfdisk is available for anonymous FTP from or
PBOOT can be found in

Choosing the "right" boot concept

Although LILO can be installed in many different ways, the choice is
usually limited by the present setup and therefore, typically only a small
number of configurations which fit naturally into an existing system
remains. The following sections describe various possible cases. See also
section "BIOS restrictions".

The configuration file /etc/lilo.conf for the examples could look like

boot = /dev/hda2
image = /vmlinuz
image = /vmlinuz.old
other = /dev/hda1
table = /dev/hda
label = msdos

It installs a Linux kernel image (/vmlinuz), an alternate Linux kernel
image (/vmlinuz.old) and a chain loader to boot MS-DOS from /dev/hda1. The
option COMPACT on the second line instructs the map installer to optimize

In all examples, the names of the IDE-type hard disk devices (/dev/hda...)
are used. Everything applies to other disk types (e.g. SCSI disks;
/dev/sda...) too.

BIOS restrictions
- - - - - - - - -

Nowadays, an increasing number of systems is equipped with comparably large
disks or even with multiple disks. At the time the disk interface of the
standard PC BIOS has been designed (about 16 years ago), such
configurations were apparently considered to be too unlikely to be worth

The most common BIOS restrictions that affect LILO are the limitation to
two hard disks and the inability to access more than 1024 cylinders per
disk. LILO can detect both conditions, but in order to work around the
underlying problems, manual intervention is necessary.

The drive limit does not exist in every BIOS. Some modern motherboards and
disk controllers are equipped with a BIOS that supports more (typically
four) disk drives. When attempting to access the third, fourth, etc. drive,
LILO prints a warning message but continues. Unless the BIOS really
supports more than two drives, the system will _not_ be able to boot in
that case.*

* However, if only "unimportant" parts of the system are located on the
"high" drives, some functionality may be available.

The cylinder limit is a very common problem with IDE disks. There, the
number of cylinders may already exceed 1024 if the drive has a capacity of
more than 504 MB. Many SCSI driver BIOSes present the disk geometry in a
way that makes the limit occur near 1 GB. Modern disk controllers may even
push the limit up to about 8 GB. All cylinders beyond the 1024th are
inaccessible for the BIOS. LILO detects this problem and aborts the
installation (unless the LINEAR option is used, see section "Global

Note that large partitions that only partially extend into the "forbidden
zone" are still in jeopardy even if they appear to work at first, because
the file system does not know about the restrictions and may allocate disk
space from the area beyond the 1024th cylinder when installing new kernels.
LILO therefore prints a warning message but continues as long as no
imminent danger exists.

There are four approaches of how such problems can be solved:

- use of a different partition which is on an accessible disk and which
does not exceed the 1024 cylinder limit. If there is only a DOS
partition which fulfills all the criteria, that partition can be used
to store the relevant files. (See section "/boot on a DOS partition".)
- rearranging partitions and disks. This is typically a destructive
operation, so extra care should be taken to make good backups.
- if the system is running DOS or Windows 95, LOADLIN can be used instead
of LILO.
- if all else fails, installation of a more capable BIOS, a different
controller or a different disk configuration.

LILO depends on the BIOS to load the following items:

- /boot/boot.b
- /boot/map (created when running /sbin/lilo)
- all kernels
- the boot sectors of all other operating systems it boots
- the startup message, if one has been defined

Normally, this implies that the Linux root file system should be in the
"safe" area. However, it is already sufficient to put all kernels into
/boot and to either mount a "good" partition on /boot or to let /boot be a
symbolic link pointing to or into such a partition.

See also /usr/src/linux/Documentation/ide.txt (or
/usr/src/linux/drivers/block/README.ide in older kernels) for a detailed
description of problems with large disks.

One disk, Linux on a primary partition
- - - - - - - - - - - - - - - - - - -

If at least one primary partition of the first hard disk is used as a Linux
file system (/, /usr, etc. but _not_ as a swap partition), the LILO boot
sector should be stored on that partition and it should be booted by the
original master boot record or by a program like BOOTACTV.

| MBR /dev/hda |
| +------------------------|
| | MS-DOS /dev/hda1 |
| |------------------------|
--> | | Linux / /dev/hda2 |

In this example, the BOOT variable could be omitted, because the boot
sector is on the root partition.

One disk, Linux on a logical partition
- - - - - - - - - - - - - - - - - - -

If no primary partition is available for Linux, but at least one logical
partition of an extended partition on the first hard disk contains a Linux
file system, the LILO boot sector should be stored in the partition sector
of the extended partition and it should be booted by the original master
boot record or by a program like BOOTACTV.

| MBR /dev/hda |
| +------------------------|
| | MS-DOS /dev/hda1 |
| |------------------------|
--> | | Extended /dev/hda2 |
| | +----------------------|
| | | Linux /dev/hda5 |
| | |----------------------|
| | | ... /dev/hda6 |

Because many disk partitioning programs refuse to make an extended
partition (in our example /dev/hda2) active, you might have to use
activate, which comes with the LILO distribution.

OS/2 BootManager should be able to boot LILO boot sectors from logical
partitions. The installation on the extended partition itself is not
necessary in this case.

Two disks, Linux (at least partially) on the first disk
- - - - - - - - - - - - - - - - - - - - - - - - - - - -

This case is equivalent to the configurations where only one disk is in the
system. The Linux boot sector resides on the first hard disk and the second
disk is used later in the boot process.

Only the location of the boot sector matters - everything else
(/boot/boot.b, /boot/map, the root file system, a swap partition, other
Linux file systems, etc.) can be located anywhere on the second disk,
provided that the constraints described in section "BIOS restrictions" are

Two disks, Linux on second disk, first disk has an extended partition
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

If there is no Linux partition on the first disk, but there is an extended
partition, the LILO boot sector can be stored in the partition sector of
the extended partition and it should be booted by the original master boot
record or by a program like BOOTACTV.

+--------------------------+ +--------------------------+
| MBR /dev/hda | | MBR /dev/hdb |
| +------------------------| | +------------------------|
| | MS-DOS /dev/hda1 | | | Linux /dev/hdb1 |
| |------------------------| | |------------------------|
--> | | Extended /dev/hda2 | | | ... /dev/hdb2 |
| | +----------------------| | | |
| | | ... /dev/hda5 | | | |
| | |----------------------| | | |
| | | ... /dev/hda6 | | | |
+--------------------------+ +--------------------------+

The program activate, that accompanies LILO, may have to be used to set the
active marker on an extended partition, because MS-DOS' FDISK and some
older version of Linux fdisk refuse to do that. (Which is generally a good

Two disks, Linux on second disk, first disk has no extended partition
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

If there is neither a Linux partition nor an extended partition on the
first disk, then there's only one place left, where a LILO boot sector
could be stored: the master boot record.

In this configuration, LILO is responsible for booting all other operating
systems too.

+--------------------------+ +--------------------------+
--> | MBR /dev/hda | | MBR /dev/hdb |
| +------------------------| | +------------------------|
| | MS-DOS /dev/hda1 | | | Linux /dev/hdb1 |
| |------------------------| | |------------------------|
| | ... /dev/hda2 | | | ... /dev/hdb2 |
+--------------------------+ +--------------------------+

You should back up your old MBR before installing LILO and verify that LILO
is able to boot your other operating system(s) before relying on this

The line boot = /dev/hda2 in /etc/lilo.conf would have to be changed to
boot = /dev/hda in this example.

More than two disks
- - - - - - - - - -

On systems with more than two disks, typically only the first two can be
accessed. The configuration choices are therefore the same as with two

When attempting to access one of the extra disks, LILO displays a warning
message ( Warning: BIOS drive 0x may not be accessible ) but does
not abort. This is done in order to allow the lucky few whose BIOS (or
controller-BIOS) does support more than two drives to make use of this
feature. By all others, this warning should be considered a fatal error.

Note that the two disks restriction is only imposed by the BIOS. Linux
normally has no problems using all disks once it is booted.

/boot on a DOS partition
- - - - - - - - - - - -

Recent kernels support all the functions LILO needs to map files also on
MS-DOS (or UMSDOS) file systems. Since DOS partitions tend to occupy
exactly the places where BIOS restrictions (see section "BIOS
restrictions") are invisible, they're an ideal location for /boot if the
native Linux file systems can't be used because of BIOS problems.

In order to accomplish this, the DOS partition is mounted read-write, a
directory (e.g. /dos/linux) is created, all files from /boot are moved to
that directory, /boot is replaced by a symbolic link to it, the kernels are
also moved to the new directory, their new location is recorded in
/etc/lilo.conf, and finally /sbin/lilo is run.

From then on, new kernels must always be copied into that directory on the
DOS partition before running /sbin/lilo, e.g. when recompiling a kernel,
the standard procedure changes from

# make zlilo


# make zImage
# mv /dos/linux/vmlinuz /dos/linux/vmlinuz.old
# mv arch/i386/boot/zImage /dos/linux/vmlinuz
# /sbin/lilo

_WARNING:_ De-fragmenting such a DOS partition is likely to make Linux or
even the whole system unbootable. Therefore, the DOS partition should
either not be de-fragmented, or a Linux boot disk should be prepared (and
tested) to bring up Linux and to run /sbin/lilo after the

* Setting the "system" attribute from DOS on the critical files (e.g.
everything in C:\LINUX) may help to protect them from being rearranged.
However, the boot floppy should still be ready, just in case.

The boot prompt

Immediately after it's loaded, LILO checks whether one of the following is

- any of the [Shift], [Control] or [Alt] keys is pressed.
- [CapsLock] or [ScrollLock] is set.

If this is the case, LILO displays the boot: prompt and waits for the name
of a boot image (i.e. Linux kernel or other operating system). Otherwise,
it boots the default boot image* or - if a delay has been specified - waits
for one of the listed activities until that amount of time has passed.

* The default boot image is either the first boot image, the image
specified with the DEFAULT variable, or the image that has been
selected at the boot prompt.

At the boot prompt, the name of the image to boot can be entered. Typing
errors can be corrected with [BackSpace], [Delete], [Ctrl U] and [Ctrl X].
A list of known images can be obtained by pressing [?] or [Tab].

If [Enter] is pressed and no file name has been entered, the default image
is booted.

Boot command-line options

LILO is also able to pass command-line options to the kernel. Command-line
options are words that follow the name of the boot image and that are
separated by spaces.


boot: linux single root=200

This document only gives an overview of boot options. Please consult Paul
Gortmaker's BootPrompt-HOWTO for a more complete and more up to date list.
You can get it from or from one
of the many mirror sites.

Standard options
- - - - - - - -

Recent kernels recognize a large number of options, among them are debug ,
no387 , no-hlt , ramdisk= , reserve=,,... ,
root= , ro , and rw . All current init programs also recognize
the option single . The options lock and vga are processed by the boot
loader itself. Boot command-line options are always case-sensitive.

single boots the system in single-user mode. This bypasses most system
initialization procedures and directly starts a root shell on the console.
Multi-user mode can typically be entered by exiting the single-user shell
or by rebooting.

root= changes the root device. This overrides settings that may
have been made in the boot image and on the LILO command line. is
either the hexadecimal device number or the full path name of the device,
e.g. /dev/hda3.*

* The device names are hard-coded in the kernel. Therefore, only the
"standard" names are supported and some less common devices may not be
recognized. In those cases, only numbers can be used.

reserve=,,... reserves IO port regions. This can be used to
prevent device drivers from auto-probing addresses where other devices are
located, which get confused by the probing.

ro instructs the kernel to mount the root file system read-only. rw
mounts it read-write. If neither ro nor rw is specified, the setting
from the boot image is used.

no-hlt avoids executing a HLT instructions whenever the system is idle.
HLT normally significantly reduces power consumption and therefore also
heat dissipation of the CPU, but may not work properly with some clone
CPUs. no387 disables using the hardware FPU even if one is present.

debug enables more verbose console logging.

Recent kernels also accept the options init= and noinitrd . init
specifies the name of the init program to execute. Therefore, if single
mode cannot be entered because init is mis-configured, one may still be
able to reach a shell using init=/bin/sh. noinitrd disables automatic
loading of the initial RAM disk. Instead, its content is then available on

vga= alters the VGA mode set at startup. The values normal ,
extended , ask or a decimal number are recognized. (See also "Booting
kernel images from a file".)

kbd=,... preloads a sequence of keystrokes in the BIOS keyboard
buffer. The keystrokes have to be entered as 16 bit hexadecimal numbers,
with the upper byte containing the scan code and the lower byte containing
the ASCII code. Note that most programs only use the ASCII code, so the
scan code can frequently be omitted. Scan code tables can be found in many
books on PC hardware. Note that scan codes depend on the keyboard layout.

Finally, lock stores the current command-line as the default
command-line, so that LILO boots the same image with the same options
(including lock ) when invoked the next time.

Device-specific options
- - - - - - - - - - - -

There is also a plethora of options to specify certain characteristics
(e.g. IO and memory addresses) of devices. Some common ones are ether ,
floppy , hd , bmouse , and sound . The usage of these options is
=,... . Please consult the corresponding FAQs and HOWTOs
for details. For an overview of all available options, consult the file
init/main.c in the kernel source tree.

Other options
- - - - - - -

Options of the type = which are neither standard options
nor device-specific options, cause the respective variables to be set in
the environment passed to init. The case of the variable name is preserved,
i.e. it isn't automatically converted to upper case.

Note that environment variables passed to init are typically available in
system initialization scripts (e.g. /etc/rc.local), but they're not visible
from ordinary login sessions, because the login program removes them from
the user's environment.

Repeating options
- - - - - - - - -

The effect of repeating boot command-line options depends on the options.*
There are three possible behaviours:

* Options are frequently repeated when a string defined with APPEND or
LITERAL is prepended to the parameters typed in by the user. Also, LILO
implicitly prepends the options ramdisk , ro , root , or rw when
RAMDISK, READ-ONLY, READ-WRITE, or ROOT, respectively, are set in the
configuration file. ( lock and vga are handled by a different
internal mechanism.)

Options that only enable or disable a certain functionality can be repeated
any number of times. debug , lock , no-hlt , and no387 fall into this

Other options change a global setting whenever they appear, so only the
value or presence of the last option matters. The antagonists ro and rw
are such options. Also, ramdisk , root , and vga work this way.
Example: ro rw would mount the root file system read-write.

Finally, when reserve and many device-specific options are repeated, each
occurrence has its own meaning, e.g. hd=... hd=... would configure two
hard disks, and reserve=0x300,8 reserve=0x5f0,16 would reserve the ranges
0x300 to 0x307 and 0x5f0 to 0x5ff (which is equivalent to writing
reserve=0x300,8,0x5f0,16 ).

Implicit options
- - - - - - - -

LILO always passes the string BOOT_IMAGE= to the kernel, where
is the name by which the kernel is identified (e.g. the label). This
variable can be used in /etc/rc to select a different behaviour, depending
on the kernel.

When booting automatically, i.e. without human intervention, the word auto
is also passed on the command line. This can be used by init to suppress
interactive prompts in the boot phase.

Boot image selection

The details of selecting the boot image are somewhat complicated. The
following tables illustrate them. First, if neither PROMPT is set nor a
shift key is being pressed:

Externally Command | Auto- Booted image
provided line in | matic
cmd. line* map file** | boot***
No No | Yes Default image
Yes - | Yes Specified by external
| command line
No Yes | Yes Specified by command line
| in map file

* Externally provided command lines could be used to add front-ends to
LILO. They would pass the respective command string to LILO, which
would then interpret it like keyboard input. This feature is currently
not used.

** This command line is set by invoking the map installer with the -R
option, by using the boot command-line option lock , or if a fallback
command line is set (with FALLBACK).

*** I.e. the keyword auto is added.

If PROMPT is not set and a shift key is being pressed:

Input Empty Extern. Cmd.l. | Auto- Booted image
timeout cmd.l. cmd.l. in map | matic
file | boot
No No - - | No Specified by the user
No Yes - - | No Default image
Yes n/a - - | Yes Default image

Finally, if the configuration variable PROMPT is set:

Input Empty Extern. Cmd.l. | Auto- Booted image
timeout cmd.l. cmd.l. in map | matic
file | boot
No No No No | No Specified by the user
No Yes No No | No Default image
Yes n/a No No | Yes Default image
n/a n/a Yes - | Yes Specified by external
| command line
n/a n/a No Yes | Yes Specified by command
| line in map file

Note that LILO pauses for the amount of time specified in DELAY when at the
end of a default command line. The automatic boot can then be interrupted
by pressing a modifier key ([Shift], [Ctrl], etc.).

The default image is the first image in the map file or the image specified
with the DEFAULT variable. However, after an unsuccessful boot attempt, the
respective image becomes the default image.

Map installer

The map installer program /sbin/lilo updates the boot sector and creates
the map file. If the map installer detects an error, it terminates
immediately and does not touch the boot sector and the map file.

Whenever the map installer updates a boot sector, the original boot sector
is copied to /boot/boot., where is the hexadecimal device
number. If such a file already exists, no backup copy is made. Similarly, a
file /boot/part. is created if LILO modifies the partition table.
(See "General per-image options".)

Command-line options

The LILO map installer can be invoked in the following ways:

Show current installation
- - - - - - - - - - - - -

The currently mapped files are listed. With -v , also many parameters are

/sbin/lilo [ -C ] -q [ -m ] [ -v ... ]

Specifies the configuration file that is used by the map installer
(see section "Configuration"). If -C is omitted, /etc/lilo.conf is
Specifies an alternate map file. See also sections "Options
corresponding to configuration variables" and "Global options".
Lists the currently mapped files.
-v ...
Increase verbosity. See also sections "Options corresponding to
configuration variables" and "Global options".

Create or update map
- - - - - - - - - -

A new map is created for the images described in the configuration file
/etc/lilo.conf and they are registered in the boot sector.

/sbin/lilo [ -C ] [ -b ] [ -c ] [ -l ] [ -i
] [ -f ] [ -m ] [ -d ] [ -v
... ] [ -t ] [ -s | -S ] [ -P fix | -P ignore ]
[ -r ]

Specifies the boot device. See also sections "Options corresponding to
configuration variables" and "Global options".
Enables map compaction. See also sections "Options corresponding to
configuration variables" and "Global options".
Specifies an alternate configuration file. See also section "Show
current installation".
Sets the delay before LILO boots the default image. Note that the
delay is specified in _tenths_ of a second. See also sections "Options
corresponding to configuration variables" and "Global options".
Specifies the default image. See also sections "Options corresponding
to configuration variables" and "Global options".
Specifies a disk parameter table file. See also sections "Options
corresponding to configuration variables" and "Global options".
Specifies an alternate boot file. See also sections "Options
corresponding to configuration variables" and "Global options".
Enables linear sector addresses. See also sections "Options
corresponding to configuration variables" and "Global options".
Specifies an alternate map file. See also sections "Options
corresponding to configuration variables" and "Global options".
Specifies how invalid partition table entries should be handled. See
also sections "Options corresponding to configuration variables" and
"Global options".
Chroots to the specified directory before doing anything else. This is
useful when running the map installer while the normal root file system
is mounted somewhere else, e.g. when recovering from an installation
failure with a recovery disk. The -r option is implied if the
environment variable ROOT is set.* The current directory is changed
to the new root directory, so using relative paths may not work.
Specifies an alternate boot sector save file. See also sections
"Options corresponding to configuration variables" and "Global
Like -s , but overwrites old save files.
Test only. This performs the entire installation procedure except
replacing the map file, writing the modified boot sector and fixing
partition tables. This can be used in conjunction with the -v option
to verify that LILO will use sane values.
-v ...
Increase verbosity. See also sections "Options corresponding to
configuration variables" and "Global options".

* E.g. if your root partition is mounted on /mnt, you can update the map
by simply running ROOT=/mnt /mnt/sbin/lilo

Change default command line
- - - - - - - - - - - - - -

Changes LILO's default command line. See also section "Boot image

/sbin/lilo [ -C ] [ -m ] -R [ ... ]

Specifies an alternate configuration file. See also section "Show
current installation".
Specifies an alternate map file. See also sections "Options
corresponding to configuration variables" and "Global options".
Stores the specified words in the map file. The boot loader uses those
words as the default command line when booting the next time. That
command line is removed from the map file by the boot loader by
overwriting the sector immediately after reading it. The first word has
to be the name of a boot image. If -R is not followed by any words,
the current default command line in the map file is erased.* If the
command line isn't valid, the map installer issues an error message and
returns a non-zero exit code.

* -R is typically used in reboot scripts, e.g.
cd /
/sbin/lilo -R "$*" && reboot

Kernel name translation
- - - - - - - - - - - -

Determines the path of the kernel.

/sbin/lilo [ -C ] -I [ ]

Specifies an alternate configuration file. See also section "Show
current installation".
-I [ ]
Translates the specified label name to the path of the corresponding
kernel image and prints that path on standard output. This can be used
to synchronize files that depend on the kernel (e.g. the ps database).
The image name can be obtained from the environment variable
BOOT_IMAGE . An error message is issued and a non-zero exit code is
returned if no matching label name can be found. The existence of the
image file is verified if the option character v is added.

- - - - - - - -

Restores the boot sector that was used before the installation of LILO.
Note that this option only works properly if LILO's directories (e.g.
/boot) have not been touched since the first installation. See also section
"LILO de-installation".

/sbin/lilo [ -C ] [ -s ] -u | -U [

Specifies an alternate configuration file. See also section "Show
current installation".
Specifies an alternate boot sector save file. See also sections
"Options corresponding to configuration variables" and "Global
-u [ ]
Restores the backup copy of the specified boot sector. If no device is
specified, the value of the boot variable is used. If this one is also
unavailable, LILO uses the current root device. The name of the backup
copy is derived from the device name. The -s option or the backup
variable can be used to override this. LILO validates the backup copy
by checking a time stamp.
-U [ ]
Like -u, but does not check the time stamp.

Print version number
- - - - - - - - - -

/sbin/lilo -V

Print the version number and exit.

Options corresponding to configuration variables
- - - - - - - - - - - - - - - - - - - - - - - -

There are also many command-line options that correspond to configuration
variables. See section "Global options" for a description.

Command-line option | Configuration variable
-b | boot=
-c | compact
-d | delay=
-D | default=
-i | install=
-l | linear
-m | map=
-P fix | fix-table
-P ignore | ignore-table
-s | backup=
-S | force-backup=
-v ... | verbose=


The configuration information is stored in the file /etc/lilo.conf and
consists of variable assignments.

- - -

The following syntax rules apply:

- flag variables consist of a single word and are followed by whitespace
or the end of the file.
- string variables consist of the variable name, optional whitespace, an
equal sign, optional whitespace, the value and required whitespace, or
the end of the file.
- a non-empty sequence of blanks, tabs, newlines and comments counts as
- variable names are case-insensitive. Values are usually case-sensitive,
but there are a few exceptions. (See below.)
- tabs and newlines are special characters and may not be part of a
variable name or a value. The use of other control characters and
non-ASCII characters is discouraged.
- blanks and equal signs may only be part of a variable name or a value
if they are escaped by a backslash or if the value is embedded in
double quotes. An equal sign may not be the only character in a name or
- an escaped tab is converted to an escaped blank. An escaped newline is
removed from the input stream. An escaped backslash (i.e. two
backslashes) is converted to a backslash. Inside quoted strings, only
double quotes, backslashes, dollar signs, and newlines can be escaped.
- quoted strings can be continued over several lines by ending each
incomplete line with a backslash. A single space is inserted in the
string for the line end and all spaces or tabs that follow immediately
on the next line.
- environment variables can be used by specifying them in the form
$ or ${}. Dollar signs can be escaped.
- comments begin with a number sign and end with the next newline. All
characters (including backslashes) until the newline are ignored.


boot = $FD
install = $MNT/boot.b
map = $MNT/map
append = "nfsroot=/home/linux-install/root \
image = $MNT/zImage

Global options
- - - - - - -

/etc/lilo.conf begins with a possibly empty global options section. Many
global options can also be set from the command line, but storing permanent
options in the configuration file is more convenient.

The following global options are recognized:

BACKUP= Copy the original boot sector to
(which may also be a device, e.g. /dev/null) instead of
BOOT= Sets the name of the device (e.g. a hard disk
partition) that contains the boot sector. If BOOT is omitted, the boot
sector is read from (and possibly written to) the device that is
currently mounted as root.
CHANGE-RULES Defines partition type numbers. See section "Partition type
change rules" for details.
COMPACT Tries to merge read requests for adjacent sectors into a single
read request. This drastically reduces load time and keeps the map
smaller. Using COMPACT is especially recommended when booting from a
floppy disk. COMPACT may conflict with LINEAR, see section "Other
DEFAULT= Uses the specified image as the default boot image. If
DEFAULT is omitted, the image appearing first in the configuration file
is used.
DELAY= Specifies the number of _tenths_ of a second LILO should
wait before booting the first image. This is useful on systems that
immediately boot from the hard disk after enabling the keyboard. LILO
doesn't wait if DELAY is omitted or if DELAY is set to zero.
DISK= Defines non-standard parameters for the specified
disk. See section "Disk geometry" for details.
FIX-TABLE Allows LILO to adjust 3D addresses in partition tables. Each
partition entry contains a 3D (sector/head/cylinder) and a linear
address of the first and the last sector of the partition. If a
partition is not track-aligned and if certain other operating systems
(e.g. PC/MS-DOS or OS/2) are using the same disk, they may change the
3D address. LILO can store its boot sector only on partitions where
both address types correspond. LILO re-adjusts incorrect 3D start
addresses if FIX-TABLE is set.

_WARNING:_ This does not guarantee that other operating systems may
not attempt to reset the address later. It is also possible that this
change has other, unexpected side-effects. The correct fix is to
re-partition the drive with a program that does align partitions to
tracks. Also, with some disks (e.g. some large EIDE disks with address
translation enabled), under some circumstances, it may even be
unavoidable to have conflicting partition table entries.
FORCE-BACKUP= Like BACKUP, but overwrite an old backup copy
if it exists. BACKUP= is ignored if FORCE-BACKUP appears
in the same configuration file.
IGNORE-TABLE Tells LILO to ignore corrupt partition tables and to put
the boot sector even on partitions that appear to be unsuitable for
INSTALL= Install the specified file as the new boot sector.
If INSTALL is omitted, /boot/boot.b is used as the default.
KEYTABLE= Re-map the keyboard as specified in this file. See
section "Keyboard translation" for details.
LINEAR Generate linear sector addresses instead of sector/head/cylinder
addresses. Linear addresses are translated at run time and do not
depend on disk geometry. Note that boot disks may not be portable if
LINEAR is used, because the BIOS service to determine the disk geometry
does not work reliably for floppy disks. When using LINEAR with large
disks, /sbin/lilo may generate references to inaccessible disk areas
(see section "BIOS restrictions"), because 3D sector addresses are not
known before boot time. LINEAR may conflict with COMPACT, see section
"Other problems".
MAP= Specifies the location of the map file. If MAP is
omitted, a file /boot/map is used.
MESSAGE= Specifies a file containing a message that is
displayed before the boot prompt. No message is displayed while waiting
for a modifier key ([Shift], etc.) after printing "LILO ". In the
message, the FF character ([Ctrl L]) clears the local screen. The
size of the message file is limited to 65535 bytes. The map file has to
be rebuilt if the message file is changed or moved.
NOWARN Disables warnings about possible future dangers.
PROMPT Forces entering the boot prompt without expecting any prior
key-presses. Unattended reboots are impossible if PROMPT is set and
TIMEOUT isn't.
SERIAL= Enables control from a serial line. The specified
serial port is initialized and LILO is accepting input from it and from
the PC's keyboard. Sending a break on the serial line corresponds to
pressing a shift key on the console in order to get LILO's attention.
All boot images should be password-protected if the serial access is
less secure than access to the console, e.g. if the line is connected
to a modem. The parameter string has the following syntax:
The components , and can be omitted. If a
component is omitted, all following components have to be omitted too.
Additionally, the comma has to be omitted if only the port number is

the number of the serial port, zero-based. 0 corresponds to
COM1 alias /dev/ttyS0, etc. All four ports can be used (if
the baud rate of the serial port. The following baud rates are
supported: 110, 300, 1200, 2400, 4800, 9600, 19200, and 38400 bps.
Default is 2400 bps.
the parity used on the serial line. LILO ignores input
parity and strips the 8th bit. The following (upper or lower case)
characters are used to describe the parity: n for no parity, e
for even parity and o for odd parity.
the number of bits in a character. Only 7 and 8 bits are
supported. Default is 8 if parity is "none", 7 if parity is "even"
or "odd".

If SERIAL is set, the value of DELAY is automatically raised to 20.

Example: serial=0,2400n8 initializes COM1 with the default parameters.
TIMEOUT= Sets a timeout (in tenths of a second) for keyboard
input. If no key is pressed for the specified time, the first image is
automatically booted. Similarly, password input is aborted if the user
is idle for too long. The default timeout is infinite.
VERBOSE= Turns on lots of progress reporting. Higher numbers give
more verbose output. If -v is additionally specified on the command
line, is increased accordingly. The following verbosity levels

<0 only warnings and errors are shown
0 prints one line for each added or skipped image
1 mentions names of important files and devices and why they are
accessed. Also displays informational messages for exceptional but
harmless conditions and prints the version number.
2 displays statistics and processing of temporary files and devices
3 displays disk geometry information and partition table change
4 lists sector mappings as they are written into the map file (i.e.
after compaction, in a format suitable to pass it to the BIOS)
5 lists the mapping of each sector (i.e. before compaction, raw)

When using the -q option, the levels have a slightly different

0 displays only image names
1 also displays all global and per-image settings
2 displays the address of the first map sector

Additionally, the kernel configuration parameters APPEND, INITRD, RAMDISK,
READ-ONLY, READ-WRITE, ROOT and VGA, and the general per-image options
in the global options section. They are used as defaults if they aren't
specified in the configuration sections of the respective images. See below
for a description.

The plethora of options may be intimidating at first, but in "normal"
configurations, hardly any options but BOOT, COMPACT, DELAY, ROOT, and VGA
are used.

General per-image options
- - - - - - - - - - - - -

The following options can be specified for all images, independent of their

ALIAS= Specifies a second name for the current entry.
FALLBACK= Specifies a string that is stored as the default
command line if the current image is booted. This is useful when
experimenting with kernels which may crash before allowing interaction
with the system. If using the FALLBACK option, the next reboot (e.g.
triggered by a manual reset or by a watchdog timer) will load a
different (supposedly stable) kernel. The command line by the fallback
mechanism is cleared by removing or changing the default command line
with the -R option, see "Change default command line".
LABEL= By default, LILO uses the main file name (without its path)
of each image specification to identify that image. A different name
can be used by setting the variable LABEL.
LOCK Enables automatic recording of boot command lines as the defaults
for the following boots. This way, LILO "locks" on a choice until it is
manually overridden.
OPTIONAL Omit this image if its main file is not available at map
creation time. This is useful to specify test kernels that are not
always present.
PASSWORD= Ask the user for a password when trying to load this
image. Because the configuration file contains unencrypted passwords
when using this option, it should only be readable for the super-user.
Passwords are always case-sensitive.
RESTRICTED Relaxes the password protection by requiring a password only
if parameters are specified on the command line (e.g. single).
RESTRICTED can only be used together with PASSWORD.
SINGLE-KEY Enables booting the image by hitting a single key, without
the need to press [Enter] afterwards. SINGLE-KEY requires that either
the image's label or its alias (or both) is a single character.
Furthermore, no other image label or alias may start with that
character, e.g. an entry specifying a label linux and an alias l is
not allowed with SINGLE-KEY. Note that you can't specify command-line
parameters for an entry for which only SINGLE-KEYed names exist.

All general per-image options, with the exception of LABEL and ALIAS, can
also be set in the global options section as defaults for all images.


password = Geheim
image = /vmlinuz
label = linux
alias = 1
other = /dev/hda1
label = dos
alias = 2

Per-image options for kernels
- - - - - - - - - - - - - - -

Each (kernel or non-kernel) image description begins with a special
variable (see section "Booting kernel images from a device") which is
followed by optional variables. The following variables can be used for all
image descriptions that describe a Linux kernel:

APPEND= Appends the options specified in to the
parameter line passed to the kernel. This is typically used to specify
parameters of hardware that can't be entirely auto-detected, e.g.
append = "hd=64,32,202"
INITRD= Specifies the file that will be loaded at boot time as the
initial RAM disk.
LITERAL= like APPEND, but removes all other options (e.g.
setting of the root device). Because vital options can be removed
unintentionally with LITERAL, this option cannot be set in the global
options section.
RAMDISK= Specifies the size of the optional RAM disk. A value of
zero indicates that no RAM disk should be created. If this variable is
omitted, the RAM disk size configured into the boot image is used.
READ-ONLY Specifies that the root file system should be mounted
read-only. Typically, the system startup procedure re-mounts the root
file system read-write later (e.g. after fsck'ing it).
READ-WRITE specifies that the root file system should be mounted
ROOT= Specifies the device that should be mounted as root.
If the special name CURRENT is used, the root device is set to the
device on which the root file system is currently mounted. If the root
has been changed with -r , the respective device is used. If the
variable ROOT is omitted, the root device setting contained in the
kernel image is used. It can be changed with the rdev program.
VGA= Specifies the VGA text mode that should be selected when
booting. The following values are recognized (case is ignored):

NORMAL select normal 80x25 text mode.
EXTENDED select 80x50 text mode. The word EXTENDED can be
abbreviated to EXT.
ASK stop and ask for user input (at boot time).
use the corresponding text mode. A list of available modes
can be obtained by booting with vga=ask and pressing [Enter].

If this variable is omitted, the VGA mode setting contained in the
kernel image is used. rdev supports manipulation of the VGA text mode
setting in the kernel image.

All kernel per-image options but LITERAL can also be set in the global
options section as defaults for all kernels.

If one of RAMDISK, READ-ONLY, READ-WRITE, ROOT, or VGA is omitted in the
configuration file and the corresponding value in the kernel image is
changed, LILO or the kernel will use the new value.

It is perfectly valid to use different settings for the same image, because
LILO stores them in the image descriptors and not in the images themselves.


image = /vmlinuz
label = lin-hd
root = /dev/hda2
image = /vmlinuz
label = lin-fd
root = /dev/fd0

Boot image types

LILO can boot the following types of images:

- kernel images from a file.
- kernel images from a block device. (E.g. a floppy disk.)
- the boot sector of some other operating system.

The image type is determined by the name of the initial variable of the
configuration section.

The image files can reside on any media that is accessible at boot time.
There's no need to put them on the root device, although this certainly
doesn't hurt.

Booting kernel images from a file
- - - - - - - - - - - - - - - - -

The image is specified as follows: IMAGE=


image = /linux

See sections "Per-image options for kernels" and "Boot image types" for the
options that can be added in a kernel image section.

Booting kernel images from a device
- - - - - - - - - - - - - - - - - -

The range of sectors that should be mapped has to be specified. Either a
range ( - ) or a start and a distance ( + ) have
to be specified. and are zero-based. If only the start is
specified, only that sector is mapped.

The image is specified as follows: IMAGE= Additionally, the
RANGE variable must be set.


image = /dev/fd0
range = 1+512

All kernel options can also be used when booting the kernel from a device.

Booting a foreign operating system
- - - - - - - - - - - - - - - - -

LILO can even boot other operating systems, i.e. MS-DOS. To boot an other
operating system, the name of a loader program, the device or file that
contains the boot sector and the device that contains the partition table
have to be specified.

The boot sector is merged with the partition table and stored in the map

Currently, the loaders chain.b and os2_d.b exist. chain.b simply starts the
specified boot sector.* os2_d.b it a variant of chain.b that can boot OS/2
from the second hard disk. The MAP-DRIVE option has to be used with os2_d.b
to actually swap the drives.

* The boot sector is loaded by LILO's secondary boot loader before
control is passed to the code of chain.b.

The image is specified as follows: OTHER= or OTHER=

In addition to the options listen in section "Per-image options for
kernels", the following variables are recognized:

CHANGE Change the partition table according to the rules specified in
this CHANGE section. This option is intended for booting systems which
find their partitions by examining the partition table. See section
"Partition type changes" for details.
LOADER= Specifies the chain loader that should be used. If
it is omitted, /boot/chain.b is used.
MAP-DRIVE= Instructs chain.b to installs a resident
driver that re-maps the floppy or hard disk drives. This way, one can
boot any operating system from a hard disk different from the first
one, as long as that operating system uses _only_ the BIOS to access
that hard disk.* This is known to work for PC/MS-DOS.

* So you should be very suspicious if the operating system requires
any specific configuration or even drivers to use the disk it is
booted from. Since there is a general trend to use optimized
drivers to fully exploit the hardware capabilities (e.g.
non-blocking disk access), booting systems from the second disk may
become increasingly difficult.

MAP-DRIVE is followed by the variable TO= which
specifies the drive that should effectively be accessed instead of the
original one. The list of mappings is only searched until the first
match is found. It is therefore possible to "swap" drives, see the
second example below.
TABLE= Specifies the device that contains the partition table.
LILO does not pass partition information to the booted operating system
if this variable is omitted. (Some operating systems have other means
to determine from which partition they have been booted. E.g. MS-DOS
usually stores the geometry of the boot disk or partition in its boot
sector.) Note that /sbin/lilo must be re-run if a partition table
mapped referenced with TABLE is modified.
UNSAFE Do not access the boot sector at map creation time. This disables
some sanity checks, including a partition table check. If the boot
sector is on a fixed-format floppy disk device, using UNSAFE avoids the
need to put a readable disk into the drive when running the map
installer. UNSAFE and TABLE are mutually incompatible.

None of these options can be set in the global options section.


other = /dev/hda2
label = dos
table = /dev/hda

other = /dev/hdb2
label = os2
loader = /boot/os2_d.b
map-drive = 0x80
to = 0x81
map-drive = 0x81
to = 0x80

Disk geometry

For floppies and most hard disks, LILO can obtain the disk geometry
information from the kernel. Unfortunately, there are some exotic disks or
adapters which may either not supply this information or which may even
return incorrect information.

If no geometry information is available, LILO reports either the error
geo_query_dev HDIO_GETGEO (dev 0x)
Device 0x: Got bad geometry //

If incorrect information is returned, booting may fail in several ways,
typically with a partial "LILO" banner message. In this document, that is
called a "geometry mismatch".

The next step should be to attempt setting the LINEAR configuration
variable or the -l command-line option. If this doesn't help, the entire
disk geometry has to be specified explicitly. Note that LINEAR doesn't
always work with floppy disks.

Another common use of disk sections is if an (E)IDE and a SCSI drive are
used in the same system and the BIOS is configured to use the SCSI drive as
the first drive. (Normally, the (E)IDE drive would be the first drive and
the SCSI drive would be the second one.) Since LILO doesn't know how the
BIOS is configured, it needs to be told explicitly about this arrangement.
(See the second example below.)

Obtaining the geometry
- - - - - - - - - - -

The disk geometry parameters can be obtained by booting MS-DOS and running
the program DPARAM.COM with the hexadecimal BIOS code of the drive as its
argument, e.g. dparam 0x80 for the first hard disk. It displays the number
of sectors per track, the number of heads per cylinder and the number of
cylinders. All three numbers are one-based.

Alternatively, the geometry may also be determined by reading the
information presented by the "setup" section of the ROM-BIOS or by using
certain disk utilities under operating systems accessing the disk through
the BIOS.

Specifying the geometry
- - - - - - - - - - - -

Disk geometry parameters are specified in the options section of the
configuration file. Each disk parameter section begins with
DISK=, similar to the way how boot images are specified. It is
suggested to group disk parameter sections together, preferably at the
beginning or the end of the options section.

For each disk, the following variables can be specified:

BIOS= Is the number the BIOS uses to refer to that
device. Normally, it's 0x80 for the first hard disk and 0x81 for
the second hard disk. Note that hexadecimal numbers have to begin with
"0x". If BIOS is omitted, LILO tries to "guess" that number.
HEADS= specify the number of sectors per track and the number of
heads, i.e. the number of tracks per cylinder. Both parameters have to
be either specified together or they have to be entirely omitted. If
omitted, LILO tries to obtain that geometry information from the
CYLINDERS= Specifies the number of cylinders. This value is
only used for sanity checks. If CYLINDERS is omitted, LILO uses the
information obtained from the kernel if geometry information had to be
requested in order to determine some other parameter. Otherwise,* it
just assumes the number of cylinders to be 1024, which is the cylinder
limit imposed by the BIOS.
INACCESSIBLE Marks the device as inaccessible (for the BIOS). This is
useful if some disks on the system can't be read by the BIOS, although
LILO "thinks" they can. If one accidentally tries to use files located
on such disks for booting, the map installer won't notice and the
system becomes unbootable. The most likely use of INACCESSIBLE is to
prevent repetition after experiencing such a situation once. No other
variables may be specified if a device is configured as INACCESSIBLE.

* I.e. if the BIOS device code, the number of sectors, the number of
heads and the partition start are specified. Note that the number of
cylinders may appear to vary if CYLINDERS is absent and only some of
the partition starts are specified.

Additionally, partition subsections can be added with
PARTITION=. Each partition section can contain only one

START= Specifies the zero-based number of the start
sector of that partition. The whole disk always has a partition offset
of zero. The partition offset is only necessary when using devices for
which the kernel does not provide that information, e.g. CD-ROMs.


disk = /dev/sda
bios = 0x80
sectors = 32
heads = 64
cylinders = 632
partition = /dev/sda1
start = 2048
partition = /dev/sda2
start = 204800
partition = /dev/sda3
start = 500000
partition = /dev/sda4
start = 900000

disk = /dev/sda
bios = 0x80
disk = /dev/hda
bios = 0x81

Partition table manipulation

Some non-Linux operating systems obtain information about their partitions
(e.g. their equivalent of the root file system) from the partition table.
If more than one such operating system is installed on a PC, they may have
conflicting interpretations of the content of the partition table. Those
problems can be avoided by changing the partition table, depending on which
operating system is being booted.

Partition table changes are specified in a CHANGE section in the
configuration file section describing the foreign operating system. Note
that CHANGE sections are only accepted if the build-time option

The CHANGE section contains subsections for each partition whose table
entry needs to be modified. Partitions are specified with

Changes are applied in the sequence in which they appear in the
configuration file. Configurations containing changes that are redundant
either by repeating a previous change or by changing its result further are
invalid and refused by the map installer.

Internally, all changes are expressed as rules which specify the location
(disk and offset in the partition table), the value this location must
contain before the change, and the value that has to be stored. As a safety
measure, the rule is ignored if the previous value is found to be

Partition activation
- - - - - - - - - -

This option is intended for booting systems which determine their boot
partition by examining the active flag in the partition table. The flag is
enabled with ACTIVATE and disabled with DEACTIVATE. Note that only the
current partition is affected. LILO does not automatically change the
active flags of other partitions and it also allows more than one partition
to be active at the same time.


other = /dev/sda4
label = sco
partition = /dev/sda4
partition = /dev/sda3

Partition type change rules
- - - - - - - - - - - - - -

Partition type changes are normally a transition between two possible
values, e.g. a typical convention is to set the lowest bit in the upper
nibble of the partition type (i.e. 0x10) in order to "hide", and to clear
it to "unhide" a partition. LILO performs these changes based on a set of
rules. Each rule defines the name of a partition type, its normal value,
and the value when hidden. Those rules are defined in the options section
of the configuration file. The section defining them begins with

The following options and variables can appear in the section:

RESET Removes all previously defined rules. This is needed if a user
doesn't wish to use the pre-defined rules (see below).
TYPE= Adds a rule for the type with the specified name. Type names
are case-insensitive. The values are defined with NORMAL= and
HIDDEN=. Values can be specified as decimal or as hexadecimal
numbers with a leading 0x . If only one of the values is present, the
other value is assumed to be the same number, but with the most
significant bit inverted.

LILO pre-defines rules for the three partition types of DOS partitions. The
following example removes the pre-defined rules and creates them again:

type = DOS12
normal = 0x01
hidden = 0x11
type = DOS16_small
normal = 4 # hidden is 0x14
type = DOS16_big
hidden = 0x16

Partition type changes
- - - - - - - - - - -

Partition type changes are specified in the partition section as
SET=_, where is the name of the partition type, and
is its state, i.e. NORMAL or HIDDEN.


other = /dev/sda3
label = dos
partition = /dev/sda2
set = dos16_big_normal
partition = /dev/sda3
set = DOS16_big_normal

Only one SET variable is allowed per partition section. In the rare event
that more than one SET variable is needed, further partition sections can
be used.

Keyboard translation

The PC keyboard emits so-called scan codes, which are basically key
numbers. The BIOS then translates those scan codes to the character codes
of the characters printed on the key-caps. By default, the BIOS normally
assumes that the keyboard has a US layout. Once an operating system is
loaded, this operating system can use a different mapping.

At boot time, LILO only has access to the basic services provided by the
BIOS and therefore receives the character codes for an US keyboard. It
provides a simple mechanism to re-map the character codes to what is
appropriate for the actual layout.*

* The current mechanism isn't perfect, because it sits on top of the
scan code to character code translation performed by the BIOS. This
means that key combinations that don't produce any useful character on
the US keyboard will be ignored by LILO. The advantage of this approach
is its simplicity.

Compiling keyboard translation tables
- - - - - - - - - - - - - - - - - - -

LILO obtains layout information from the keyboard translation tables Linux
uses for the text console. They are usually stored in
/usr/lib/kbd/keytables. LILO comes with a program that reads
those tables and generates a table suitable for use by the map installer. invokes the program loadkeys to print the tables in a format
that is easy to parse.*

* On some systems, only root can execute loadkeys. It is then necessary
to run as root too. is used as follows: [ -p = ] ...
[][.] ]
[][.] ]

-p =
Specifies corrections ("patches") to the mapping obtained from the
translation table files. E.g. if pressing the upper case "A" should
yield an at sign, -p 65=64 would be used. The -p option can be
repeated any number of times. The codes can also be given as
hexadecimal or as octal numbers if they are prefixed with 0x or 0,
The directory in which the file resides. The default path is
Usually the trailing .map, which is automatically added if
the file name doesn't contain dots.
Is the layout which specifies the translation by the
BIOS. If none is specified, us is assumed.
Is the actual layout of the keyboard. writes the resulting translation table as a binary string to
standard output. Such tables can be stored anywhere with any name, but the
suggested naming convention is /boot/.ktl ("Keyboard Table for Lilo"),
where is the name of the keyboard layout.

Example: de >/boot/de.ktl

Using keyboard translation tables
- - - - - - - - - - - - - - - - -

The keyboard translation table file is specified with the global
configuration option keytable= . The complete name of the file
has to be given.


keytable = /boot/de.klt

Installation and updates


This section describes the installation of LILO. See section "LILO
de-installation" for how to uninstall LILO.

- - - - - - -

The kernel header files have to be in /usr/include/linux and the kernel
usually has to be configured by running make config before LILO can be

/bin/sh has to be a real Bourne shell. bash is sufficiently compatible, but
some ksh clones may cause problems.

A file named INCOMPAT is included in the distribution. It describes
incompatibilities to older versions of LILO and may also contain further
compatibility notes.

Quick installation
- - - - - - - - -

If you want to install LILO on your hard disk and if you don't want to use
all its features, you can use the quick installation script. Read QuickInst
for details.

QuickInst can only be used for first-time installations or to entirely
replace an existing installation, _not_ to update or modify an existing
installation of LILO. Be sure you've extracted LILO into a directory that
doesn't contain any files of other LILO installations.

- - -

Some of the files contained in lilo-21.tar.gz:

This documentation in plain ASCII format. Some sections containing
complex tables are only included in the LaTeX version in doc/user.tex
List of incompatibilities to previous versions of LILO.
Change history.
The version number of the respective release.
Quick installation script.
The LSM ("Linux Software Map") entry of the respective LILO release.
Makefile to generate everything else.
lilo/*.c, lilo/*.h
LILO map installer C source and common header files.
LILO boot loader assembler source.
C source of a simple boot partition setter.
Assembler source of a disk parameter dumper.
Shell script used to create the current LILO distribution.
Perl script to generate keyboard translation tables.
Description of how to generate the documentation.
Makefile used to convert the LaTeX source into either DVI output or
the plain ASCII README file.
LaTeX source of LILO's user's guide (this document).
LaTeX source of LILO's technical overview.
Various xfig pictures used in the technical overview.
Style file to save a few square miles of forest.
Shell script that invokes LaTeX repeatedly until all references have
Perl script to convert the LaTeX source of the user's guide to plain

Files created after make in lilo/ (among others):

Combined boot sector. make install puts this file into /boot
Generic chain loader. make install puts this file into /boot
Chain loader to load OS/2 from the second hard disk. make install
puts this file into /boot
LILO (map) installer. make install puts this file into /sbin
Simple boot partition setter.
MS-DOS executable of the disk parameter dumper.

Normal first-time installation
- - - - - - - - - - - - - - -

First, you have to install the LILO files:

- extract all files from lilo-.tar.gz in a new directory.*
- configure the Makefile (see section "Build-time configuration")
- run make to compile and assemble all parts.
- run make install to copy all LILO files to the directories where
they're installed. /sbin should now contain the file lilo, /usr/sbin
should contain, and /boot should contain boot.b,
chain.b, and os2_d.b.

* E.g. /usr/src/lilo

If you want to use LILO on a non-standard disk, you might have to determine
the parameters of your disk(s) and specify them in the configuration file.
See section "Disk geometry" for details. If you're using such a
non-standard system, the next step is to test LILO with the boot sector on
a floppy disk:

- insert a blank (but low-level formatted) floppy disk into /dev/fd0.
- run echo image= |
/sbin/lilo -C - -b /dev/fd0 -v -v -v
If you've already installed LILO on your system, you might not want to
overwrite your old map file. Use the -m option to specify an
alternate map file name.
- reboot. LILO should now load its boot loaders from the floppy disk and
then continue loading the kernel from the hard disk.

Now, you have to decide, which boot concept you want to use. Let's assume
you have a Linux partition on /dev/hda2 and you want to install your LILO
boot sector there. The DOS-MBR loads the LILO boot sector.

- get a working boot disk, e.g. an install or recovery disk. Verify that
you can boot with this setup and that you can mount your Linux
partition(s) with it.
- if the boot sector you want to overwrite with LILO is of any value
(e.g. it's the MBR or if it contains a boot loader you might want to
use if you encounter problems with LILO), you should mount your boot
disk and make a backup copy of your boot sector to a file on that
floppy, e.g. dd if=/dev/hda of=/fd/boot_sector bs=512 count=1
- create the configuration file /etc/lilo.conf, e.g.

Be sure to use absolute paths for all files. Relative paths may cause
unexpected behaviour when using the -r option.
- now, you can check what LILO would do if you were about to install it
on your hard disk:
/sbin/lilo -v -v -v -t
- if you need some additional boot utility (i.e. BOOTACTV), you should
install that now
- run /sbin/lilo to install LILO on your hard disk
- if you have to change the active partition, use fdisk or activate to do
- reboot

Build-time configuration
- - - - - - - - - - - -

Certain build-time parameters can be configured. They can either be edited
in the top-level Makefile or they can be stored in a file
/etc/lilo.defines. Settings in the Makefile are ignored if that file

The following items can be configured:

BEEP Enables beeping after displaying "LILO". This is useful on
machines which don't beep at the right time when booting and when
working over a serial console. This option is disabled by default.
IGNORECASE Makes image name matching case-insensitive, i.e. "linux"
and "Linux" are identical. This option is enabled by default. Note that
password matching is always case-sensitive.
LARGE_EDBA Loads LILO at a lower address in order to leave more space
for the EBDA (Extended BIOS Data Area). This is necessary on some
recent MP systems. Note that enabling LARGE_EDBA reduces the maximum
size of "small" images (e.g. "Image" or "zImage").
NO1STDIAG Do not generate diagnostics on read errors in the first
stage boot loader. This avoids possibly irritating error codes if the
disk controller has transient read problems. This option is disabled by
NODRAIN The boot loader empties the keyboard buffer when starting,
because it may contain garbage on some systems. Draining the keyboard
buffer can be disabled by setting the NODRAIN option. NODRAIN is
disabled by default.
NOINSTDEF If the option INSTALL is omitted, don't install a new boot
sector, but try to modify the old boot sector instead. This option is
disabled by default.
ONE_SHOT Disables the command-line timeout (configuration variable
TIMEOUT) if any key is pressed. This way, very short timeouts can be
used if PROMPT is set. ONE_SHOT is disabled by default.
READONLY Disallows overwriting the default command line sector of the
map file. This way, command lines set with -R stay in effect until
they are explicitly removed. READONLY also disables LOCK, FALLBACK,
and everything enabled by REWRITE_TABLE . This option is disabled by
REWRITE_TABLE Enables rewriting the partition table at boot time. This
may be necessary to boot certain operating systems who expect the
active flag to be set on their partition or who need changes in
partition types. See also section "Partition table manipulation". This
option is _dangerous_ and it is disabled by default.
USE_TMPDIR Use the directory indicated in the TMPDIR environment
variable when creating temporary device files. If TMPDIR is not set
or if LILO is compiled without USE_TMPDIR , temporary device files are
created in /tmp.* This option is disabled by default.
VARSETUP Enables the use of variable-size setup segments. This option
is enabled by default and is only provided to fall back to fixed-size
setup segments in the unlikely case of problems when using prehistoric
XL_SECS= Enable support for extra large (non-standard) floppy
disks. The number of sectors is set in the BIOS disk parameter table to
the specified value. Note that this hack may yield incorrect behaviour
on some systems. This option is disabled by default.

* Note that, while honoring TMPDIR is the "right" thing to do, the
fact that LILO has to create temporary device files at all may indicate
that the operating environment is not completely set up, so TMPDIR
may point to an invalid location.

/etc/lilo.defines should be used if one wishes to make permanent
configuration changes. The usual installation procedures don't touch that
file. Example:


After changing the build-time configuration, LILO has to be recompiled with
the following commands:

make spotless

Floppy disk installation
- - - - - - - - - - - -

In some cases*, it may be desirable to install LILO on a floppy disk in a
way that it can boot a kernel without accessing the hard disk.

* E.g. if no hard disk is accessible through the BIOS.

The basic procedure is quite straightforward (see also section "BIOS

- a file system has to be created on the file system
- the kernel and boot.b have to be copied to the floppy disk
- /sbin/lilo has to be run to create the map file

This can be as easy as

/sbin/mke2fs /dev/fd0
[ -d /fd ] || mkdir /fd
mount /dev/fd0 /fd
cp /boot/boot.b /fd
cp /zImage /fd
echo image=/fd/zImage label=linux |
/sbin/lilo -C - -b /dev/fd0 -i /fd/boot.b -c -m /fd/map
umount /fd

The command line of /sbin/lilo is a little tricky. -C - takes the
configuration from standard input (naturally, one could also write the
configuration into a file), -b /dev/fd0 specifies that the boot sector is
written to the floppy disk, -i /fd/boot.b takes the first and second
stage loaders from the floppy, -c speeds up the load process, and -m
/fd/map puts the map file on the floppy too.


LILO is affected by updates of kernels, the whole system and (trivially) of
LILO itself. Typically, only /sbin/lilo has to be run after any of those
updates and everything will be well again (at least as far as LILO is

LILO update
- - - - - -

Before updating to a new version of LILO, you should read at least the file
INCOMPAT which describes incompatibilities with previous releases.

After that, the initial steps are the same as for a first time
installation: extract all files, configure the Makefile, run make to
build the executables and run make install to install the files.

The old versions of boot.b, chain.b, etc. are automatically renamed to
boot.old, chain.old, etc. This is done to ensure that you can boot even if
the installation procedure does not finish. boot.old, chain.old, etc. can
be deleted after the map file is rebuilt.

Because the locations of boot.b, chain.b, etc. have changed and because the
map file format may be different too, you have to update the boot sector
and the map file. Run /sbin/lilo to do this.

Kernel update
- - - - - - -

Whenever any of the kernel files that are accessed by LILO is moved or
overwritten, the map has to be re-built.* Run /sbin/lilo to do this.

* It is advisable to keep a second, stable, kernel image that can be
booted if you forget to update the map after a change to your usual
kernel image.

The kernel has a make target "zlilo" that copies the kernel to /vmlinuz and
runs /sbin/lilo.

System upgrade
- - - - - - -

Normally, system upgrades (i.e. installation or removal of packages,
possibly replacement of a large part of the installed binaries) do not
affect LILO. Of course, if a new kernel is installed in the process, the
normal kernel update procedure has to be followed (see section "Kernel
update"). Also, if kernels are removed or added, it may be necessary to
update the configuration file.

If LILO is updated by this system upgrade, /sbin/lilo should be run before
booting the upgraded system. It is generally a good idea not to rely on the
upgrade procedure to perform this essential step automatically.

However, system upgrades which involve removal and re-creation of entire
partitions (e.g. /, /usr, etc.) are different. First, they should be
avoided, because they bear a high risk of losing other critical files, e.g.
the /etc/XF86Config you've spent the last week fiddling with. If an upgrade
really has to be performed in such a brute-force way, this is equal with
total removal of LILO, followed by a new installation. Therefore, the
procedures described in the sections "LILO de-installation" and "LILO
update" have to be performed. If you've forgotten to make a backup copy of
/etc/lilo.conf before the destructive upgrade, you might also have to go
through section "Normal first-time installation" again.

LILO de-installation

In order to stop LILO from being invoked when the system boots, its boot
sector has to be either removed or disabled. All other files belonging to
LILO can be deleted _after_ removing the boot sector, if desired.*

* Backup copies of old boot sectors may be needed when removing the boot
sector. They are stored in /boot.

Again, _when removing Linux, LILO must be de-installed before (!) its files
(/boot, etc.) are deleted._ This is especially important if LILO is
operating as the MBR.

LILO 14 (and newer) can be de-installed with lilo -u. If LILO 14 or newer
is currently installed, but the first version of LILO installed was older
than 14, lilo -U may work. When using -U, the warning at the end of this
section applies.

If LILO's boot sector has been installed on a primary partition and is
booted by the "standard" MBR or some partition switcher program, it can be
disabled by making a different partition active. MS-DOS' FDISK, Linux fdisk
or LILO's activate can do that.

If LILO's boot sector is the master boot record (MBR) of a disk, it has to
be replaced with a different MBR, typically MS-DOS' "standard" MBR. When
using MS-DOS 5.0 or above, the MS-DOS MBR can be restored with FDISK /MBR.
This only alters the boot loader code, not the partition table.

LILO automatically makes backup copies when it overwrites boot sectors.
They are named /boot/boot., with corresponding to the device
number, e.g. 0300 is /dev/hda, 0800 is /dev/sda, etc. Those backups can
be used to restore the old MBR if no easier method is available. The
commands are
dd if=/boot/boot.0300 of=/dev/hda bs=446 count=1 or
dd if=/boot/boot.0800 of=/dev/sda bs=446 count=1

_WARNING:_ Some Linux distributions install boot. files from the
system where the distribution was created. Using those files may yield
unpredictable results. Therefore, the file creation date should be
carefully checked.

Installation of other operating systems

Some other operating systems (e.g. MS-DOS 6.0) appear to modify the MBR in
their install procedures. It is therefore possible that LILO will stop to
work after such an installation and Linux has to be booted from floppy
disk. The original state can be restored by either re-running /sbin/lilo
(if LILO is installed as the MBR) or by making LILO's partition active (if
it's installed on a primary partition).

It is generally a good idea to install LILO after the other operating
systems have been installed. E.g. OS/2 is said to cause trouble when
attempting to add it to an existing Linux system. (However, booting from
floppy and running /sbin/lilo should get around most interferences.)

Typically, the new operating system then has to be added to LILO's
configuration (and /sbin/lilo has to be re-run) in order to boot it.

See also section "Other problems" for a list of known problems with some
other operating systems.


All parts of LILO display some messages that can be used to diagnose

Map installer warnings and errors

Most messages of the map installer (/sbin/lilo) should be self-explanatory.
Some messages that indicate common errors are listed below. They are
grouped into fatal errors and warnings (non-fatal errors).

Fatal errors
- - - - - -

Boot sector of doesn't have a boot signature
Boot sector of doesn't have a LILO signature
The sector from which LILO should be uninstalled doesn't appear to be
a LILO boot sector.
Can't put the boot sector on logical partition
An attempt has been made to put LILO's boot sector on the current root
file system partition which is on a logical partition. This usually
doesn't have the desired effect, because common MBRs can only boot
primary partitions. This check can be bypassed by explicitly specifying
the boot partition with the -b option or by setting the configuration
variable BOOT.
Checksum error
The descriptor table of the map file has an invalid checksum. Refresh
the map file _immediately_ !
Device 0x: Configured as inaccessible.
There is a DISK section entry indicating that the device is
inaccessible from the BIOS. You should check carefully that all files
LILO tries to access when booting are on the right device.
Device 0x: Got bad geometry //
The device driver for your SCSI controller does not support geometry
detection. You have to specify the geometry explicitly (see section
"Disk geometry").
Device 0x: Invalid partition table, entry
The 3D and linear addresses of the first sector of the specified
partition don't correspond. This is typically caused by partitioning a
disk with a program that doesn't align partitions to tracks and later
using PC/MS-DOS or OS/2 on that disk. LILO can attempt to correct the
problem, see "General per-image options".
Device 0x: Partition type 0x does not seem suitable for
a LILO boot sector
The location where the LILO boot sector should be placed does not seem
to be suitable for that. (See also also section "Disk organization").
You should either adjust the partition type to reflect the actual use
or put the boot sector on a different partition. This consistency check
only yields a warning (i.e. LILO continues) if the option IGNORE-TABLE
is set.
is not a valid partition device
The specified device is either not a device at all, a whole disk, or a
partition on a different disk than the one in whose section its entry
is not a whole disk device
Only the geometry of whole disks (e.g. /dev/hda, /dev/sdb, etc.) can
be redefined when using DISK sections.
DISKTAB and DISK are mutually exclusive
You cannot use a disktab file and disk geometry definitions in the
configuration file at the same time. Maybe /etc/disktab was
accidentally used, because that's the default for
backward-compatibility. You should delete /etc/disktab after completing
the transition to DISK sections.
Duplicate entry in partition table
A partition table entry appears twice. The partition table has to be
fixed with fdisk.
Duplicate geometry definition for
A disk or partition geometry definition entry for the same device
appears twice in the configuration file. Note that you mustn't write a
partition section for the whole disk - its start sector is always the
first sector of the disk.
First sector of doesn't have a valid boot signature
The first sector of the specified device does not appear to be a valid
boot sector. You might have confused the device name.*
geo_comp_addr: Cylinder beyond end of media ()
A file block appears to be located beyond the last cylinder of the
disk. This probably indicates an error in the disk geometry
specification (see section "Disk geometry") or a file system
geo_comp_addr: Cylinder number is too big ( > 1023)
Blocks of a file are located beyond the 1024th cylinder of a hard
disk. LILO can't access such files, because the BIOS limits cylinder
numbers to the range 0...1023. Try moving the file to a different
place, preferably a partition that is entirely within the first 1024
cylinders of the disk.
Hole found in map file ()
The map installer is confused about the disk organization. Please
report this error.
doesn't have a valid LILO signature
The specified item has been located, but is not part of LILO.
has an invalid stage code ()
The specified item has probably been corrupted. Try re-building LILO.
is version . Expecting version .
The specified entity is either too old or too new. Make sure all parts
of LILO (map installer, boot loaders and chain loaders) are from the
same distribution. **
Kernel is too big
The kernel image (without the setup code) is bigger than 512 kbytes
(or 448 kbytes, if built with LARGE_EDBA ). LILO would overwrite
itself when trying to load such a kernel. This limitation only applies
to old kernels which are loaded below 0x10000 (e.g. "Image" or
"zImage"). Try building the kernel with "bzImage". If this is
undesirable for some reason, try removing some unused drivers and
compiling the kernel again. This error may also occur if the kernel
image is damaged or if it contains trailing "junk", e.g. as the result
of copying an entire boot floppy to the hard disk.
LOCK and FALLBACK are mutually exclusive
Since LOCK and FALLBACK both change the default command line, they
can't be reasonably used together.
Map is not a regular file.
This is probably the result of an attempt to omit writing a map file,
e.g. with -m /dev/null . The -t option should be used to accomplish
Must specify SECTORS and HEADS together
It is assumed that disks with a "strange" number of sectors will also
have a "strange" number of heads. Therefore, it's all or nothing.
No geometry variables allowed if INACCESSIBLE
If a device is configured as INACCESSIBLE (see section "Specifying the
geometry"), its DISK section must not contain any geometry variables.
No image is defined
The command line specified either with the -R option or with
FALLBACK does not contain the name of a valid image. Note that optional
images which have not been included in the map file are not considered
as valid.
Partition entry not found
The partition from which an other operating system should be booted
isn't listed in the specified partition table. This either means that
an incorrect partition table has been specified or that you're trying
to boot from a logical partition. The latter usually doesn't work. You
can bypass this check by omitting the partition table specification
(e.g. omitting the variable TABLE).
Single-key clash: "" vs. ""
The specified image labels or aliases conflict because one of them is
a single character and has the SINGLE-KEY option set, and the other
name begins with that character.
Sorry, don't know how to handle device
LILO uses files that are located on a device for which there is no
easy way to determine the disk geometry. Such devices have to be
explicitly described, see section "Disk geometry".
This LILO is compiled READONLY and doesn't support ...
If LILO is not allowed to write to the disk at boot time (see section
"Build-time configuration"), options like LOCK and FALLBACK are
This LILO is compiled without REWRITE_TABLE and doesn't support ...
If LILO is not allowed to rewrite partition tables at boot time (see
section "Partition table manipulation"), options like ACTIVATE and SET
(in a CHANGE section) are unavailable. You may also get this error if
LILO is compiled with READONLY enabled.
Timestamp in boot sector of differs from date of
The backup copy of the boot sector does not appear to be an ancestor
of the current boot sector. If you are absolutely sure that the boot
sector is indeed correct, you can bypass this check by using -U
instead of -u .
Trying to map files from unnamed device 0x (NFS ?)
This is probably the same problem as described below, only with the
root file system residing on NFS.
Trying to map files from your RAM disk. Please check -r option or ROOT
environment variable.
Most likely, you or some installation script is trying to invoke LILO
in a way that some of the files is has to access reside on the RAM
disk. Normally, the ROOT environment variable should be set to the
mount point of the effective root device if installing LILO with a
different root directory. See also sections "Create or update map" and
"Normal first-time installation".
VGA mode presetting is not supported by your kernel.
Your kernel sources appear to be very old ('93 ?). LILO may work on
your system if you remove the VGA option.
write :
The disk is probably full or mounted read-only.

* Because different partition programs may display the partitions in a
different order, it is possible that what you think is your first
partition isn't /dev/hda1, etc. A good method to verify the content of
a partition is to try to mount it.

** The expected version number may be different from the version number
of the LILO package, because file version numbers are only increased
when the file formats change.

- - - -

Messages labeled with "Warning" can be turned off with the NOWARN option.

FIGETBSZ : < error_reason>
The map installer is unable to determine the block size of a file
system. It assumes a block size of two sectors (1kB).
Ignoring entry ''
The command-line option corresponding to the specified variable is
set. Therefore, the configuration file entry is ignored.
Setting DELAY to 20 (2 seconds)
Because accidentally booting the wrong kernel or operating system may
be very inconvenient on systems that are not run from a local display,
the minimum delay is two seconds if the SERIAL variable is set.
(temp) :
Deleting a temporary file has failed for the specified reason.
Warning: BIOS drive 0x may not be accessible
Because most BIOS versions only support two floppies and two hard
disks, files located on additional disks may be inaccessible. This
warning indicates that some kernels or even the whole system may be
Warning: COMPACT may conflict with LINEAR on some systems
Please see section "Other problems" for a description of this problem.
Warning: should be owned by root
In order to prevent users from compromising system integrity, the
configuration file should be owned by root and write access for all
other users should be disabled.
Warning: should be readable only for root if using
Users should not be allowed to read the configuration file when using
the PASSWORD option, because then, it contains unencrypted passwords.
Warning: should be writable only for root
See " Warning: should be owned by root ".
Warning: device 0x exceeds 1024 cylinder limit
A disk or partition exceeds the 1024 cylinder limit imposed by the
BIOS. This may result in a fatal error in the current installation run
or in later installation runs. See " geo_comp_addr: Cylinder number is
too big ( > 1023) " for details.
Warning: is not on the first disk
The specified partition is probably not on the first disk. LILO's boot
sector can only be booted from the first disk unless some special boot
manager is used.
WARNING: The system is unbootable !
One of the last installation steps has failed. This warning is
typically followed by a fatal error describing the problem.

Boot loader messages

The boot loader generates three types of messages: progress and error
messages while it is loading, messages indicating disk access errors, and
error messages in response to invalid command-line input. Since messages of
the latter type are usually self-explanatory, only the two other categories
are explained.

LILO start message
- - - - - - - - -

When LILO loads itself, it displays the word "LILO". Each letter is printed
before or after performing some specific action. If LILO fails at some
point, the letters printed so far can be used to identify the problem. This
is described in more detail in the technical overview.

Note that some hex digits may be inserted after the first "L" if a
transient disk problem occurs. Unless LILO stops at that point, generating
an endless stream of error codes, such hex digits do not indicate a severe

() No part of LILO has been loaded. LILO either isn't installed
or the partition on which its boot sector is located isn't active.
L ... The first stage boot loader has been loaded and started,
but it can't load the second stage boot loader. The two-digit error
codes indicate the type of problem. (See also section "Disk error
codes".) This condition usually indicates a media failure or a geometry
mismatch (e.g. bad disk parameters, see section "Disk geometry").
LI The first stage boot loader was able to load the second stage boot
loader, but has failed to execute it. This can either be caused by a
geometry mismatch or by moving /boot/boot.b without running the map
LIL The second stage boot loader has been started, but it can't load
the descriptor table from the map file. This is typically caused by a
media failure or by a geometry mismatch.
LIL? The second stage boot loader has been loaded at an incorrect
address. This is typically caused by a subtle geometry mismatch or by
moving /boot/boot.b without running the map installer.
LIL- The descriptor table is corrupt. This can either be caused by a
geometry mismatch or by moving /boot/map without running the map
LILO All parts of LILO have been successfully loaded.

Disk error codes
- - - - - - - -

If the BIOS signals an error when LILO is trying to load a boot image, the
respective error code is displayed. The following BIOS error codes are

0x00 "Internal error". This code is generated by the sector read
routine of the LILO boot loader whenever an internal inconsistency is
detected. This might be caused by corrupt files. Try re-building the
map file. Another possible cause for this error are attempts to access
cylinders beyond 1024 while using the LINEAR option. See section "BIOS
restrictions" for more details and for how to solve the problem.
0x01 "Illegal command". This shouldn't happen, but if it does, it may
indicate an attempt to access a disk which is not supported by the
BIOS. See also "Warning: BIOS drive 0x may not be accessible"
in section "Warnings".
0x02 "Address mark not found". This usually indicates a media problem.
Try again several times.
0x03 "Write-protected disk". This should only occur on write
0x04 "Sector not found". This typically indicates a geometry mismatch.
If you're booting a raw-written disk image, verify whether it was
created for disks with the same geometry as the one you're using. If
you're booting from a SCSI disk or a large IDE disk, you should check,
whether LILO has obtained correct geometry data from the kernel or
whether the geometry definition corresponds to the real disk geometry.
(See section "Disk geometry".) Removing COMPACT may help too. So may
adding LINEAR.
0x06 "Change line active". This should be a transient error. Try
booting a second time.
0x07 "Invalid initialization". The BIOS failed to properly initialize
the disk controller. You should control the BIOS setup parameters. A
warm boot might help too.
0x08 "DMA overrun". This shouldn't happen. Try booting again.
0x09 "DMA attempt across 64k boundary". This shouldn't happen. Try
omitting the COMPACT option.
0x0C "Invalid media". This shouldn't happen and might be caused by a
media error. Try booting again.
0x10 "CRC error". A media error has been detected. Try booting several
times, running the map installer a second time (to put the map file at
some other physical location or to write "good data" over the bad
spot), mapping out the bad sectors/tracks and, if all else fails,
replacing the media.
0x11 "ECC correction successful". A read error occurred, but was
corrected. LILO does not recognize this condition and aborts the load
process anyway. A second load attempt should succeed.
0x20 "Controller error". This shouldn't happen.
0x40 "Seek failure". This might be a media problem. Try booting again.
0x80 "Disk timeout". The disk or the drive isn't ready. Either the
media is bad or the disk isn't spinning. If you're booting from a
floppy, you might not have closed the drive door. Otherwise, trying to
boot again might help.
0xBB "BIOS error". This shouldn't happen. Try booting again. If the
problem persists, removing the COMPACT option or adding/removing LINEAR
might help.

If the error occurred during a write operation, the error code (two hex
digits) is prefixed with a "W". Although write errors don't affect the boot
process, they might indicate a severe problem, because they usually imply
that LILO has tried to write to an invalid location. If spurious write
errors occur on a system, it might be a good idea to configure LILO to run
read-only (see section "Build-time configuration").

Generally, invalid geometry and attempts to use more than two disks without
a very modern BIOS may yield misleading error codes. Please check carefully
if /sbin/lilo doesn't emit any warnings. Then try using the LINEAR option
(see section "Global options").

Other problems

This section contains a collection of less common problems that have been
observed. See also section "Installation of other operating systems" for
general remarks on using LILO with other operating systems. Some of the
problems are obscure and so are the work-arounds.

- If LILO doesn't go away even if you erase its files, format your Linux
partition, etc., you've probably installed LILO as your MBR and you've
forgotten to deinstall it before deleting its files. See section "LILO
de-installation" for what you can do now.
- For yet unknown reasons, LILO may fail on some systems with AMI BIOS if
the "Hard Disk Type 47 RAM area" is set to "0:300" instead of "DOS 1K".
- Some disk controller BIOSes perform disk geometry/address translations
that are incompatible with the way the device's geometry is seen from
Linux, i.e. without going through the BIOS. Particularly, large IDE
disks and some PCI SCSI controllers appear to have this problem. In
such cases, either the translated geometry has to be specified in a
DISK section or the sector address translation can be deferred by using
the LINEAR option. In a setup where floppies are not normally used for
booting, the LINEAR approach should be preferred, because this avoids
the risk of specifying incorrect numbers.
- OS/2 is said to be bootable from a logical partition with LILO acting
as the primary boot selector if LILO is installed on the MBR, the OS/2
BootManager is on an active primary partition and LILO boots
BootManager. Putting LILO on an extended partition instead is said to
crash the OS/2 FDISK in this scenario.

Note that booting LILO from BootManager (so BootManager is the primary
selector) or booting OS/2 directly from a primary partition (without
BootManager) should generally work. See also section "Installation of
other operating systems".
- Windows NT is reported to be bootable with LILO when LILO acts as the
MBR and the Windows NT boot loader is on the DOS partition. However,
NT's disk manager complains about LILO's MBR when trying to edit the
partition table.
- Some PC UNIX systems (SCO and Unixware have been reported to exhibit
this problem) depend on their partition being active. See section
"Partition table manipulation" for how this can be accomplished.
- Future Domain TMC-1680 adapters with the BIOS versions 3.4 and 3.5
assign BIOS device numbers in the wrong order, e.g. on a two-disk
system, /dev/sda becomes 0x81 and /dev/sdb becomes 0x80 . This can
be fixed with the following DISK section:
disk=/dev/sda bios=0x81 disk=/dev/sdb bios=0x80
Note that this is only valid for a two-disk system. In three-disk
systems, /dev/sdc would become 0x80 , etc. Also, single-disk systems
don't have this problem (and the "fix" would break them).
- Some BIOSes don't properly recognize disks with an unusual partition
table (e.g. without any partition marked active) and refuse to boot
from them. This can also affect the second hard disk and the problem
may only occur if the system is booted in a particular way (e.g. only
after a cold boot).
- On some systems, using LINEAR and COMPACT together leads to a boot
failure. The exact circumstances under which this happens are still
- If the kernel crashes after booting on a multi-processor system, LILO
may have overwritten data structures set up by the BIOS. Try the option
LARGE_EBDA in this case.