Appendix G. Configuring a Dual-Boot System

Sharing a computer between two operating systems requires dual booting. You can use either operating system on the computer, but not both at once. Each operating system boots from and uses its own hard drives or disk partitions.

This chapter explains how to configure your system to boot into both Red Hat Linux and another operating system. For clarity, we will assume that the other operating system is Microsoft Windows^TM. But the general procedures are similar for other operating systems.

	Note
	If Red Hat Linux will coexist on your system with OS/2, you must create your disk partitions with the OS/2 partitioning software — otherwise, OS/2 may not recognize the disk partitions. During the installation, do not create any new partitions, but do set the proper partition types for your Linux partitions using fdisk.

If you do not have any operating systems installed on your computer, install Windows first and then install Red Hat Linux.

If you are installing Windows 9x or Windows ME, you can not define partitions during the Windows installation. Install Windows, and then refer to the section called Partitioning with FIPS for instructions on using fips to repartition your hard drive and create free space for Linux.
If you are installing Windows NT or Windows 2000, you can create partitions of a specific size for Windows. Leave enough free space (space that is not partitioned or formatted) on the hard drive to install Linux.

	Tip
	While partitioning your hard drive, keep in mind that the BIOS in some systems cannot access more than the first 1024 cylinders on a hard drive. If this is the case, leave enough room for the `/boot` Linux partition on the first 1024 cylinders of your hard drive to boot Linux. The other Linux partitions can be after cylinder 1024.

Refer to the section called Step 3 - Do You Have Enough Disk Space? in Chapter 1 to determine how much disk space to leave. After installing Windows, refer to the section called Installing Red Hat Linux in a Dual-Boot Environment.

If the computer you want to install Red Hat Linux on is currently running Windows (or some other operating system), you have an important decision to make. Your choices are:

Do you want Red Hat Linux to be the only operating system on your computer, despite the fact that you already have Windows on your computer? If yes, you do not have to configure a dual-boot system. Backup any information that you want to save and start the installation. During the installation, if you choose to have the installation program automatically partition your system on the Disk Partitioning Setup screen, choose Remove all partitions on this system. If you choose manual partitioning with Disk Druid or fdisk, delete all the existing DOS (Windows) partitions and then create your Linux partitions.
Do you want to install Red Hat Linux and then have the option of booting either Red Hat Linux or your other operating system? A Red Hat Linux installation can be performed so that Red Hat Linux is installed on your system, but the other operating system is not affected. Since you already have Windows installed, you need to allocate disk space for Linux. Refer to the section called Allocating Disk Space for Linux, and then refer to the section called Installing Red Hat Linux in a Dual-Boot Environment.

Allocating Disk Space for Linux

	Warning
	Remember to back up all important information before reconfiguring your hard drive. Be sure to create a boot disk for both operating systems in case the boot loader fails to recognize either of them.

If you already have Windows installed on your system, you need free hard drive space on which to install Red Hat Linux. Your choices are as follows:

Add a new hard drive.
Use an existing hard drive or partition.
Create a new partition.

For all three options, be aware that the BIOS in some older systems cannot access more than the first 1024 cylinders on a hard drive. If this is the case, the /boot Linux partition must be located on the first 1024 cylinders of your hard drive to boot Linux.

Add a New Hard Drive

The simplest way to make room for Red Hat Linux is to add a new hard drive to the computer and then install Red Hat Linux on that drive. For example, if you add a second IDE hard drive to the computer, the Red Hat Linux installation program will recognize it as hdb and the existing drive (the one used by Windows) as hda. (For SCSI hard drives, the newly installed hard drive would be recognized as sdb and the other hard drive as sda.)

If you choose to install a new hard drive for Linux, all you need to do is start the Red Hat Linux installation program. After starting the Red Hat Linux installation program, just make sure you tell it to install Linux on the newly installed hard drive (such as hdb or sdb) rather than the hard drive used by Windows.

Use an Existing Hard Drive or Partition

Another way to make room for Linux is to use a hard drive or disk partition that is currently being used by Windows. For example, suppose that Windows Explorer shows two hard drives, C: and D:. This could indicate either that the computer has two hard drives, or a single hard drive with two partitions. In either case (assuming the hard drive is large enough), you can install Red Hat Linux on the hard drive or disk partition that Windows recognizes as D:.

This choice is available to you only if the computer has two or more hard drives or disk partitions.

	Note
	Windows uses letters to refer to removable drives (for example, a ZIP drive) and network storage (virtual drives) as well as for local hard drive space; you cannot install Linux on a removable or network drive.

If a local Windows partition is available in which you want to install Linux, complete the following steps:

Copy all data you want to save from the selected hard drive or partition (D: in this example) to another location.
Start the Red Hat Linux installation program and tell it to install Linux in the designated drive or partition — in this example, in the hard drive or partition that Windows designates as D:. Note that Linux distinguishes between hard drives and disk partitions. Thus:
- If C: and D: on this computer refer to two separate hard drives, the installation program will recognize them as hda and hdb (IDE) or sda and sdb (SCSI). Tell the installation program to install on hdb or sdb.
- If C: and D: refer to partitions on a single drive, the installation program will recognize them as hda1 and hda2 (or sda1 and sda2). During the partitioning phase of the Red Hat Linux installation, delete the second partition (hda2 or sda2), then partition the unallocated free space for Linux. You do not have to delete the second partition prior to starting the Red Hat Linux installation.

Create a New Partition

The third way to make room for Linux is to create a new partition for Red Hat Linux on the hard drive being used by the other operating system. If Windows Explorer shows only one hard drive (C:), and you do not want to add a new hard drive, you must partition the drive. After partitioning, Windows Explorer will see a smaller C: drive; and, when you run the Red Hat Linux installation program, you can partition the remainder of the drive for Linux.

You can use a destructive partitioning program, such as fdisk, to divide the hard drive, but doing so will require you to re-install Windows. (This is probably not your best option.)

A number of non-destructive third-party partitioning programs are available for the Windows operating system. If you choose to use one of these, consult their documentation.

For instructions on how to partition with FIPS, a program that is on the Red Hat Linux CD-ROM, refer to the section called Partitioning with FIPS.