Selecting a Boot Loader

The next item you can change is the configuration of the boot loader. A boot loader is central to the deployment of Linux as it controls the booting of operating systems on the PC. To customize the boot loader that is used by your SUSE installation, you must click the Booting heading in YaST's Expert Installation Settings panel, or click the Change button and select Booting from the pop-up menu. Doing either of these displays the pane shown in Figure 1-20, YaST's Boot Loader Settings screen.

Boot loader settings

Boot loader settings

Linux systems typically use one of two boot loaders, LILO (Linux Loader) or GRUB (Grand Unified Boot Loader). Both are very powerful and flexible, and are controlled by easily edited configuration files (/etc/lilo.conf and /boot/grub/menu.lst, respectively). The key difference between the two boot loaders is how they interact with these configuration files. If you use LILO and update its configuration file, you must rerun the lilo command to update the system boot information that is stored on your disk. GRUB automatically rereads its configuration file whenever you boot your system and therefore does not require that you update any other system boot information. GRUB is the default boot loader on SUSE systems, and unless you have special reasons to do so, you will probably not want to change this.

YaST will already have configured your boot loader, depending on your system configuration. This includes any Windows installations that have been found: they will automatically be included in the boot menu.

Two types of configuration changes are possible here: the type of boot loader and its location (see Figure 1-21) and the details of each boot entry in the Section Management tab.

FIGURE 1-21

Boot loader configuration open5U5E 11.0

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Recent versions of openSUSE use generic boot code in the Master Boot Record and then install the boot loader by default to the boot record of the /boot partition. This requires the partition to be marked as bootable in the partition table. If you wish instead to install the boot loader to the MBR, you can select that option here.

In the Section Management tab you can edit the details of each boot entry. In particular, if you know that your hardware requires a special kernel parameter at boot time such as acpi = off, you can add it here.

In general, you should not change the location of the boot loader unless you are setting up a complex multiboot system, but it is possible that you might want to change details of the kernel line in the boot entry if you know what you are doing.

1 j ,'■ - - - Two common kernel parameters that we have come across in recent years are noht

' - ~ ■"■> ■ and noacpi. Both of these parameters are relevant to modern machines. The first, noht, will turn off Linux's support of the Intel processor's hyperthreading feature. In certain processor-bound workloads, it is better to turn off hyperthreading to improve performance. The second, noacpi, turns off Linux's ACPI infrastructure. ACPI is the Advanced Configuration and Power Interface and is a standardized way for an operating system to control machine power, BIOS settings, and so on. In some rare situations, ACPI actually stops Linux from booting on certain machines. Using the boot loader configuration to set these parameters enables you to control this before a system is installed.

When you make any changes on the Boot Loader setup screen, click the Finish button to return to the standard YaST installer screen.

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