Learning Red Hat Enterprise Linux & Fedora, Fourth Edition

Boot Parameters

Boot parameters are specified using a three-part directive that includes the name of the parameter and an optional list of options, which consists of an equal sign (=) followed by a comma-separated list of option values

No spaces may appear in the directive. As an example, the following directive specifies the identity of the Linux root partition:

root=/dev/hda1

The installation program generally refers to partitions by using labels, so that you can boot a system even if you move the partitions around. A root directive referring to a label looks like this:

root=LABEL=/usr

You can specify multiple directives by separating them with a space. For example, the following specifies the identity of the Linux root partition and that the root partition is initially mounted read-only, so that a thorough check of its filesystem can be performed:

root=/dev/hda1 ro

Most directives are interpreted by the kernel, though GRUB is also capable of processing directives. If you specify a directive that neither the kernel nor GRUB understands (assuming you’re using GRUB), a directive that includes an equal sign is passed to the init process as an environment variable. You learned about environment variables in Chapter 12. A nonkernel directive that doesn’t include an equal sign is passed to the init process. An example of this usage is specifying the directive single, which causes init to start your system in single-user mode:

root=/dev/hda1 ro single

General Boot Arguments

Table C-2 describes ...