# Boot Loader Installation

In order to boot your Red Hat Linux system without a boot disk, you usually need to install a boot loader. You can choose to install either GRUB (selected by default) or LILO.

New to Red Hat Linux 7.2, GRUB is a software boot loader that can be used to start Red Hat Linux on your computer. It can also start other operating systems, such as Windows 9`x`. Here, you will be asked how (or whether) you want to configure a boot loader and which one (GRUB or LILO).

Choose which boot loader you want to install. If you would rather use the legacy boot loader, LILO, make sure it is selected instead of GRUB.

If you choose not to install a boot loader, make sure you create a boot disk at the end of this installation or have another way to boot (such as a third party boot loader) your Red Hat Linux system.

Figure 3-9. Boot Loader Installation

Now that you have chosen to install a boot loader (GRUB or LILO), you must determine where it will be installed. You may install your boot loader in one of two places:

The master boot record (MBR)

  The recommended place to install a boot loader, unless the MBR already starts another operating system loader, such as System Commander or OS/2's Boot Manager. The MBR is a special area on your hard drive that is automatically loaded by your computer's BIOS, and is the earliest point at which the boot loader can take control of the boot process. If you install it in the MBR, when your machine boots, GRUB (or LILO) will present a boot prompt. You can then boot Red Hat Linux or any other operating system that you have configured the boot loader to boot.

The first sector of your root partition

  Recommended if you are already using another boot loader on your system (such as OS/2's Boot Manager). In this case, your other boot loader will take control first. You can then configure that boot loader to start GRUB (or LILO), which will then boot Red Hat Linux.

Select where you would like GRUB (or LILO) to be installed on your system. If your system will use only Red Hat Linux, you should choose the MBR. For systems with Windows 95/98, you should also install the boot loader to the MBR so that it can boot both operating systems.

| Caution
| If you choose not to install GRUB or LILO for any reason, you will not be able to boot your Red Hat Linux system directly, and you will need to use another boot method (such as a boot diskette). Use this option only if you are sure you have another way of booting your Red Hat Linux system!

If you wish to add default options to GRUB or LILO's boot command, enter them into the Kernel parameters field. Any options you enter will be passed to the Linux kernel every time it boots.

The Force use of LBA32 (not normally required) option allows you to exceed the 1024 cylinder limit for the `/boot` partition. If you have a system which supports the LBA32 extension for booting operating systems above the 1024 cylinder limit, you want to place your `/boot` partition above this limit, and the installation program has not already detected this extension from your BIOS, you should select this option.

Every bootable partition is listed, including partitions used by other operating systems. The partition holding your Red Hat Linux system's root filesystem will have a Boot label of `linux`. Other partitions may also have boot labels. If you would like to add boot labels for other partitions (or change an existing boot label), click once on the partition to select it. Once selected, you can change the boot label.

| Note
| The Boot label column lists what you must enter at the boot prompt in order to boot the desired operating system. However, if you forget the boot labels defined on your system, you can always press [Tab] at the prompt to display a list of defined boot labels.

## Rescue Mode

If you need to use rescue mode, there are several options available to you.

- Using the CD-ROM to boot, type `linux rescue` at the `boot:` prompt.

- Using the network boot disk, type `linux rescue` at the `boot:` prompt. You will then be prompted to retrieve the rescue image from the network.

- Using the boot disk included with the Red Hat Linux boxed set, type `linux rescue` at the `boot:` prompt. You then pick an installation method and choose a valid installation tree to load from.

For more information regarding rescue mode, refer to the Official Red Hat Linux Customization Guide.

## Alternative Boot Loaders

If you do not wish to use GRUB or LILO to boot your Red Hat Linux system, you have several alternatives:

Boot disk

  As previously stated, you can use the boot disk created by the installation program (if you elected to create one).

LOADLIN

  You can load Linux from MS-DOS. Unfortunately, it requires a copy of the Linux kernel (and an initial RAM disk, if you have a SCSI adapter) to be available on an MS-DOS partition. The only way to accomplish this is to boot your Red Hat Linux system using some other method (for example, from LILO on a diskette) and then copy the kernel to an MS-DOS partition. LOADLIN is available from ftp://metalab.unc.edu/pub/Linux/system/boot/dualboot/ and associated mirror sites.

SYSLINUX

  SYSLINUX is an MS-DOS program very similar to LOADLIN. It is also available from ftp://metalab.unc.edu/pub/Linux/system/boot/loaders/ and associated mirror sites.

Some commercial boot loaders

  You can load Linux using commercial boot loaders. For example, System Commander and Partition Magic are able to boot Linux (but still require GRUB or LILO to be installed in your Linux root partition).

## SMP Motherboards, GRUB, and LILO

This section is specific to SMP motherboards only. If the installation program detects an SMP motherboard on your system, it will automatically create two `/boot/grub/grub.conf` or `/etc/lilo.conf` entries (depending on the boot loader you installed), rather than the usual single entry.

The two entries in `grub.conf` will be `Red Hat Linux (`kernel version`)` and `Red Hat Linux (`kernel versions`-smp)`. The `Red Hat Linux (`kernel version`-smp)` will boot by default. However, if you have trouble with the SMP kernel, you can elect to boot the `Red Hat Linux (`kernel version`)` entry instead. You will retain all the functionality as before, but you will only be operating with a single processor.

The two entries in `lilo.conf` will be `linux` and `linux-up`. The `linux` will boot by default. However, if you have trouble with the SMP kernel, you can elect to boot the `linux-up` entry instead. You will retain all the functionality as before, but you will only be operating with a single processor.

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