Running Linux, Third 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, such as (not necessarily the same, and not necessarily in the same order):

Console: 16 point font, 480 scans Console: colour VGA+ 80x30, 1 virtual console (max 63) pcibios_init : BIOS32 Service Directory structure at 0x000fb1d0 pcibios_init : BIOS32 Service Directory entry at 0xfb5a0 pcibios_init : PCI BIOS revision 2.00 entry at 0xfb5d0 Probing PCI hardware. Calibrating delay loop.. ok - 36.04 BogoMIPS Memory: 14984k/16384k available (552k kernel code, 384k reserved,\ 464k data) Swansea University Computer Society NET3.035 for Linux 2.0 NET3: Unix domain sockets 0.13 for Linux NET3.035. Swansea University Computer Society TCP/IP for NET3.034 IP Protocols: ICMP, UDP, TCP VFS: Diskquotas version dquot_5.6.0 ...