Section 32.3. Objective 3: Troubleshooting Boot Loaders

32.3. Objective 3: Troubleshooting Boot Loaders

In this section we cover the problems you might come across in the boot stages. Both LILO and GRUB are covered, because you'll need both for the test.

One of the most common installation problems outside of hardware support relates to LILO, the LInux LOader. Occasionally, a disk sector is bad and LILO doesn't install to it properly. Other times, it doesn't work because it was misconfigured.

One of the best ways to troubleshoot your LILO problems is to watch the output of LILO itself. Watch for your LILO prompt. If you don't see any part of the LILO prompt, LILO didn't load. Otherwise, the characters in the prompt tell you how far LILO got:

L

The first-stage boot loader is loaded and started.

LI

The second-stage boot loader is loaded.

LIL

The second-stage boot loader is started.

LIL?

The second-stage boot loader was loaded at an incorrect address.

LIL-

The descriptor table is corrupt.

LILO

All of LILO has been loaded correctly.

A very common problem LILO users run into is forgetting to rerun /sbin/lilo whenever a change is made to /etc/lilo.conf. This problem, along with the cryptic error messages of LILO, was a major factor in the design of GRUB.

GRUB, the GRand Unified Bootloader, is a user-friendly replacement for LILO. GRUB boots in three stages: Stage 1, Stage 1.5, and Stage 2.

Stage 1 errors are typically errors in reading Stage 1.5 or Stage 2 from the disk. Pressing Ctrl-Alt-Del will reboot the system.

A Stage 2 error prints an error message and continues or waits for the user to fix the problem. There are 34 error messages, listed in detail in Chapter 14 of the GRUB manual, which can be found at http://www.gnu.org/software/grub/manual/html_node/Stage2-errors.html#Stage2-errors.

A Stage 1.5 error prints an error number corresponding to one of the 34 error messages from Stage 2.