Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Guida di Installazione Scaricare il pdf (Pagina 81)

Chapter 4. GRUB 81

4.2.3. GRUB’s Root Filesystem

Some users are confused by the use of the term "root ﬁlesystem" with GRUB. It is important to

remember that GRUB’s root ﬁlesystem has nothing to do with the Linux root ﬁlesystem.

The GRUB root ﬁlesystem is the root partition for a particular device. GRUB uses this information to

mount the device and load ﬁles from it, among other things.

With Red Hat Linux, once GRUB has loaded its root partition that contains the Linux kernel, the

kernel command can be executed with the location of the kernel ﬁle as an option. Once the Linux

kernel boots, it sets its own root ﬁlesystem, and that is the one most people associate with Linux. The

original GRUB root ﬁlesystem and its mounts are forgotten. They only existed to boot the kernel ﬁle.

Refer to the root and kernel commands in Section 4.4 for more information.

4.3. Interfaces

GRUB features three powerful interfaces that provide different levels of functionality. Each of these

interfaces allows users to boot operating systems, and even move between interfaces within the GRUB

environment.

4.3.1. Menu Interface

If GRUB was automatically conﬁgured by the Red Hat Linux installation program, this is the inter-

face shown by default. A menu of operating systems or kernels preconﬁgured with their own boot

commands exists in this interface as a list, by name, after the system ﬁrst starts. Use the arrow keys

to select an option other than the default selection and press the [Enter] key to boot it. Alternatively, a

timeout period may have been set, so that GRUB will start loading the default option.

From the menu interface, press the [e] key to edit the commands in the highlighted menu entry or the

[c] key to load a command line interface.

4.3.2. Menu Entry Editor Interface

To access the menu entry editor, press the [e] key from the boot loader menu. The GRUB commands

for that entry are displayed here, and users may alter these command lines before booting the operating

system by adding ([o] after the current line; [O] before it), editing ([e]), or deleting ([d]) them.

After all changes are made, hit the [b] key to execute the commands and boot the operating system.

The [Esc] key discards any changes and reloads the standard menu interface. The [c] key will load the

command line interface.

Tip

For information about changing runlevels with GRUB using the menu entry editor, refer to Section

3.2.3.

4.3.3. Command Line Interface

The command line is the most basic GRUB interface, but it is also the one that grants the most control.

The command line makes it possible to type any relevant GRUB commands followed by the [Enter]

key to execute them. This interface features some advanced shell-like features, including [Tab] key

completion, based on context, and [Ctrl] key combinations when typing commands, such as [Ctrl]-[a]

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Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Guida di Installazione Pagina 81