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Überhacker II, Chapter 3: How to Get Many Operating Systems on One PC

In this chapter you will learn about:

· The BIOS
· Hard drives
· How to install more than one IDE hard drive on a computer
· File systems
· The expensive but easy way
· The Partition Commander/System Commander Way
· The SuSE Solution for Linux plus Windows XP and 2000 all on the same drive
· How to make a triple boot disk the harder way
· How to create a triple boot system without boot magic or system commander
· Become a computer recycling center
· Run virtual machines at the same time on one computer

Why put a whole bunch of operating systems on one PC? I do it to be able to reconfigure my network by rebooting its computers to the operating systems needed for the experiments of the day.

Once upon a time this wasn't easy. Hard drives were small. The BIOS (Basic Input/Output System) that is the heart of any PC used to be designed for one, and only one operating system and only tiny hard drives. Today's PCs make it super easy.

Word of warning: in this chapter you may want to do things to the inside of your computer. Don't forget to use a grounding strap and TURN THE COMPUTER OFF. Also, some computers (those that can be turned on from across a LAN) leave power on to the motherboard even when power is "off." So unless you are certain your computer has no power to the motherboard, unplug it from the power source.

Also, you may murder your operating system.

This chapter is not for sissies.


The most important part of your multiboot computer may be its BIOS. It is usually kept in a PROM, EPROM, EEPROM or Flash ROM. The BIOS configuration information is kept on a CMOS chip kept powered up by a tiny battery. The BIOS is what tells your computer on startup how to recognize and integrate all the components of the system. For multiboot computers, the significant part of this task is how it recognizes the floppy, CD/DVD whatever drives (most BIOSes just call them cdroms), IDE (Integrated Drive Electronics) and SCSI (Small Computer Systems Interface) hard drives, and how it chooses from which one to boot the operating system.

Some BIOSes are too primitive to easily boot more than two or three operating systems. Some, on older computers, won't even allow you to install many operating systems unless you engage in extreme measures. Here's to tell how good the BIOS is.

On bootup, the first thing you should see and remember is the type of BIOS your computer runs. Next, look on the screen for instructions on what key to hit (usually "delete") to get into the BIOS setup. According to Tom Massey, "It can be an F key, a combination of Ctrl, Alt, etc. Best to watch carefully what's displayed on your monitor during bootup. Older machines may not display the info you need to get into BIOS setup, so you may have to do some tricky web searching, post to newsgroups and so on."

On the settings for your hard drives, check to see if they let you specify LBA (logical block addressing) or autodetect. If so, you are in luck. This means you can use hard drives larger than 2.1 gigs. If not, and if you can't upgrade your BIOS to handle LBA, forget about putting three operating systems on one hard drive. You won't have enough space to do anything worthwhile, and you are stuck with an ancient drive that is literally dying to crash. However, that doesn't mean your wimpy old computer is ready for the recycle bin.

Mike Orton has a solution:

The Big bear group, a small computer firm in Wales, UK, e-mail: thebeargroup@firenet.uk.com, sells RAID cards for 13 UK pounds. These will enable you to add up to four 120 Gig IDEs to a 486, using its BIOS to run the HD's. It can be configured to run like this, not as a proper RAID card. However I don't know how well it works with several O/S on it…of course the 486 will be too slow for any MS system above Windoze 3.x But it is another option if your BIOS won't run a large HD. There must be sources in the USA and Europe.

Tom Massey has another solution: "Linux doesn't rely on the BIOS to talk to hard drives. Stick the latest version of LILO on your MBR (master boot record) and disk size isn't a problem."

However, Tanvir Ahmed says, "LILO is getting archaic. Redhat does not support it anymore. GRUB seems to be the future and a hacker favorite."

Regardless of whether your BIOS handles LBA, it is worth it to get online and look up the web site of the manufacturer of your BIOS. You may be in for a pleasant surprise. You may find that the manufacturer will make it easy for you to upgrade your BIOS to handle even larger hard drives. Now you will know whether that tempting 100 Gig hard drive will be compatible with your computer.

Next, before you do anything else, look to see if your BIOS offers virus protection. BIOS virus protection will cause your computer to raise a fuss if the master boot record of any of your disks is about to be modified. You are going to have to modify your master boot record - many times - which will be much easier if your BIOS isn't fighting you. If it is there, be sure to disable virus protection.

If at all possible, get a computer that has a BIOS that will let you boot from the drive of your choice. While LILO can be helpful, if you are building a system that uses other means to boot, this will make life much easier.

The ability to set the devices from which it can boot and the order in which it looks for a bootable device is often under a heading such as "BIOS features setup." You need to be able to boot from the CD or DVD drive. A boot option of "cdrom" will enable boot from a CD-ROM, CD-R, CD-RW or DVD drive. Installation of most operating systems requires boot from "cdrom." You can sometimes get around this by creating a boot floppy, but it is painful.

If you have a choice, use a computer whose BIOS lets you choose which IDE hard drive you boot by device name: IDE0, IDE1, IDE2, IDE3. Choices of C, D, E, or F are a bad idea. If you partition a hard drive, your operating system will have different drive letter designations than your BIOS uses. This can create confusion when you want to specify a boot disk.

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