Creating a Boot Disk

When you're logged in as root, you might want to take a few minutes to create a fresh boot disk or copy the boot disk you already have.

There are a number of reasons you should make a boot disk. It can help you recover from a system failure, it can help you test a new kernel you've downloaded and compiled, and it can help you share your computer with more than one operating system.

You were given the opportunity to make a boot disk when you installed Red Hat Linux. If you chose not to make a boot disk at installation, here's your chance to start from scratch.

To create a boot disk:

Go to a shell prompt and make sure you're logged in as root. At the shell prompt, if you see something like [newuser@localhost newuser]$, for example, type:

[newuser@localhost newuser]$ su -
Password: yourrootpassword
[root@localhost newuser]# 

Put a standard diskette in the floppy drive.

	Naming The Floppy Drive
	In Linux, the floppy drive is referred to as /dev/fd0.

If you have previously used the diskette, remember that you will lose everything on the diskette!

At the prompt, type:

uname -r

Your kernel version will be displayed. The kernel is the heart of any Linux system. Your kernel version will be something similar to:

2.4.x-yy

There will be several numbers after 2.4, for example: 2.4.1).

Now that you've found the kernel version, you can tell the mkbootdisk command which kernel to copy to your diskette.

Type the following command:

mkbootdisk --device /dev/fd0 2.4.x-yy

If you don't tell mkbootdisk where to copy the kernel, it will default to copying to the diskette in /dev/fd0.

Press [Enter]. When the light on your floppy drive goes off, remove and label the disk.

	Clearing The Screen
	If your screen becomes crowded, you can always start with a clean slate by typing clear at the prompt.

The su and su - Commands

The command su means substitute users, and it lets you temporarily log in as another user. When you type su all by itself and press [Enter], you become root (also called the superuser) while still inside your login shell. Typing su - makes you become root with root's login shell — that is, it's as if you had logged in as root. What's the difference? There are some commands which can be performed only if you've logged in as root; so typing su - allows you to perform these commands without logging out and logging back in.