Linux in a Nutshell, Fifth Edition

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Chapter 4: Boot Methods

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

rw Mount the root filesystem read/write. If neither ro nor rw is specified, the

default value (usually rw) stored in the kernel image is used.

single

Start Linux in single-user mode. This option is used for system administra-

tion and recovery. It gives you a root prompt as soon as the system boots,

with minimal initialization. No other logins are allowed.

initrd: Using a RAM Disk

Modern Linux distributions use a modular kernel, which allows modules to be

added without requiring that the kernel be rebuilt. If your root filesystem is on a

device whose driver is a module (as is frequently true of SCSI disks), you can use

the initrd facility, which provides a two-stage boot process, to first set up a

temporary root filesystem in a RAM disk containing the modules you need to add

(e.g., the SCSI driver) and then load the modules and mount the real root file-

system. The RAM disk containing the temporary filesystem is the special device

file /dev/initrd.

Similarly, you need to use a RAM disk if your root partition uses the ext3 file-

system and ext3 was not compiled into the kernel image. In that case, the ext3

module must be loaded with initrd.

Before you can use initrd, both RAM disk support (CONFIG_BLK_DEV_

RAM=y) and initial RAM disk support (CONFIG_BLK_DEV_INITRD=y ...