Running Linux, Fourth Edition

System Startup and Initialization

In this section, we’re going to talk about exactly what happens when the system boots. Understanding this process and the files involved is important for performing various kinds of system configuration.

Kernel Boot Messages

The first step is booting the kernel. As described in the previous section, this can be done from floppy or hard drive. As the kernel loads into memory, it will print messages to the system console, but usually also saves them in the system log files as well. As root, you can always check the file /var/log/messages (which contains kernel messages emitted during runtime as well). The command dmesg prints out the last lines of the kernel message ring buffer; directly after booting, naturally, you will get the boot messages.

In the following few paragraphs, we’ll go through a couple of the more interesting messages and explain what they mean. These messages are all printed by the kernel itself, as each device driver is initialized. The exact messages printed depend on what drivers are compiled into your kernel and what hardware you have on your system. You are likely to have more, fewer or different messages; we’ll concentrate here on the messages that are quite common.

The line:

Linux version 2.4.10-64GB-SMP (root@SMP_X86.suse.de) \
(gcc version 2.95.3 20010315) #1 SMP Fri Sep 28 17:26:36 GMT 2001

tells you the version number of the kernel, on which machine, when, and with which compiler it was built.

Next, the kernel reports which ...