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GRUB is a boot loader for Linux and other
operating systems that’s growing increasingly popular. It’s even
becoming the standard for numerous distributions.

Unlike LILO, the other popular boot loader,
GRUB is extremely flexible. GRUB allows you to manipulate boot
commands during the booting process, which can be quite a help
during troubleshooting.

When you start the computer and the GRUB boot
manager appears, you can halt the loading of the default boot
stanza by pressing [Esc]. Then highlight any stanza, and enter E to edit it.

GRUB will offer a list of options for the
specific stanza, taken straight from the /boot/grub/menu.lst file.
For example, you may see something like the following:

root (hd0,0)
kernel /vmlinuz ro root=/dev/hdc5 vga=788 noapic acpi=ht
initrd /initrd.img

Use the cursor to highlight each line, and
enter E to edit the

The advantages are obvious: If you install a
kernel that hangs, you can edit the file and provide the name of an
alternate kernel, or alternate options for the kernel, without
first rebooting and modifying a configuration file, which you would
have to do if using LILO.

Once you’ve edited the file to suit your needs,
enter B to boot the
entry. If you change your mind about editing a particular entry,
press [Esc] to return to the main menu.