Red Hat ENTERPRISE LINUX 5 - VIRTUAL SERVER ADMINISTRATION, Руководство по установке

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Chapter 9. The GRUB Boot Loader
98
Menu Interface
This is the default interface shown when GRUB is configured by the installation program. A menu
of operating systems or preconfigured kernels are displayed as a list, ordered by name. Use the
arrow keys to select an operating system or kernel version and press the
Enter
key to boot it. If
you do nothing on this screen, then after the time out period expires GRUB will load the default
option.
Press the
e
key to enter the entry editor interface or the
c
key to load a command line interface.
Refer to
Section 9.7, “GRUB Menu Configuration File”
for more information on configuring this
interface.
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 a command line (
o
inserts a new line after the current line
and
O
inserts a new line before it), editing one (
e
), or deleting one (
d
).
After all changes are made, the
b
key executes the commands and boots the operating system.
The
Esc
key discards any changes and reloads the standard menu interface. The
c
key loads the
command line interface.
Note
For information about changing runlevels using the GRUB menu entry editor, refer to
Section 9.8, “Changing Runlevels at Boot Time”
.
Command Line Interface
The command line interface 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
to move to the beginning of a line and
Ctrl
+
e
to move to the end of
a line. In addition, the arrow,
Home
,
End
, and
Delete
keys work as they do in the
bash
shell.
Refer to
Section 9.6, “GRUB Commands”
for a list of common commands.
9.5.1. Interfaces Load Order
When GRUB loads its second stage boot loader, it first searches for its configuration file. Once found,
the menu interface bypass screen is displayed. If a key is pressed within three seconds, GRUB builds
a menu list and displays the menu interface. If no key is pressed, the default kernel entry in the GRUB
menu is used.
If the configuration file cannot be found, or if the configuration file is unreadable, GRUB loads the
command line interface, allowing the user to type commands to complete the boot process.
If the configuration file is not valid, GRUB prints out the error and asks for input. This helps the user
see precisely where the problem occurred. Pressing any key reloads the menu interface, where it is
then possible to edit the menu option and correct the problem based on the error reported by GRUB. If
the correction fails, GRUB reports an error and reloads the menu interface.