"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     ftp://tsx-11.mit.edu/pub/linux/dos_utils/lodlin<n>.tar.gz     ftp://sunsite.unc.edu/pub/Linux/system/boot/dualboot/lodlin<n>.tgz     BOOT.SYS is available for anonymous FTP from     ftp://ftp.funet.fi/pub/Linux/tools/boot142.zip  **  LILO can be found in     ftp://tsx-11.mit.edu/pub/linux/packages/lilo/lilo-<n>.tar.gz     ftp://sunsite.unc.edu/pub/Linux/system/boot/lilo/lilo-<n>.tar.gz     ftp://lrcftp.epfl.ch/pub/linux/local/lilo/lilo-<n>.tar.gz  ***  pfdisk is available for anonymous FTP from     ftp://sunsite.unc.edu/pub/Linux/utils/disk-management/pfdisk.tar.Z or     ftp://ftp.funet.fi/pub/Linux/tools/pfdisk.tar.Z     PBOOT can be found in     ftp://ftp.funet.fi/pub/Linux/tools/pboot.zipChoosing 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 this:boot = /dev/hda2compactimage = /vmlinuzimage = /vmlinuz.oldother = /dev/hda1  table = /dev/hda  label = msdosIt 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 loading.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 supporting.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 options").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 met.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.                 FIRST DISK                     SECOND DISK        +--------------------------+    +--------------------------+        | 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 idea.)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.                 FIRST DISK                     SECOND DISK        +--------------------------+    +--------------------------+    --> | 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 approach.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 disks.When attempting to access one of the extra disks, LILO displays a warning message ( Warning: BIOS drive 0x<number> 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 zliloto# make zImage# mv /dos/linux/vmlinuz /dos/linux/vmlinuz.old# mv arch/i386/boot/zImage /dos/linux/vmlinuz# /sbin/lilo