How to Run Multiple Operating Systems


Running multiple operating systems on one computer couples the

strengths and capabilities of those OS’s while

requiring that you only buy one computer. Who

hasn’t been running one OS and wished that they could run a program that only runs under another? Who hasn’t experienced an OS problem and

wished they

could boot into another system to resolve it?


computer refurbishing, running multiple OS’s allows you to

combine the strengths of an existing Windows install with those of open

source. Case in point: Windows XP is aging but still has

active forums,

tons of how-to websites, great ease-of-use, thousands of applications,

and drivers for every device. Keeping it retains the original

software license, the installed applications, and the existing drivers.

(Past articles have described how to secure and

performance tune mature Windows systems.)

Add a Linux distribution and you gain all the

benefits of open source software — a free and currently supported operating


a state-of-the-art OS that runs on older hardware

than Windows 7 or Vista, security without anti-malware overhead, and

tons of free applications. A well-chosen distro greatly

expands the capabilities of an aging Windows computer.

Here are the ways to run multiple operating systems on a single system …

Live CDs and Live DVDs

Live CDs and Live DVDs allow you to easily boot and run alternate

operating systems. Just download a bootable OS image, burn it to disk,

set your computer to boot from the optical disc drive, and you’re


and running.

One big benefit to Live CDs is that you’re guaranteed a

malware-free OS. Some experts

now recommend

against doing your banking and finances online, or they say you should

not use Windows if you do. Live CDs offer higher security for online

banking. Every time you boot from the Live CD you initialize a

fresh uncontaminated system, because the read-only disc can not be

altered by malware. (Of course the original Live CD has to be virus-free but I have yet to hear of such contamination.)

You don’t have to alter anything on your existing hard disks to run a


CD. No fiddling with partitions. You don’t even have to mount your internal disk.

Live CDs are a risk-free way to try out and play with as

many different OS’s as you’re willing to burn CDs for.

Whether you’ll be happy with the performance of running an OS from CD

or DVD depends on the speed of your optical drive and the OS you run.

Most people are satisfied using current optical drives, even for

full-sized Linux distributions that continually access the disc while

running. If you’re refurbishing an old computer

and frequently run live CDs, check the speed of your

optical drive and get a newer one if you need to. Drive speed has

dramatically increased over the past


Another trick is to use a distro that runs entirely from memory and

never accesses the CD/DVD or hard disk after booting. Puppy Linux, for

example, runs entirely in memory

on systems having just 256 M or more. It performs well even on

older computers. After booting you can use the CD drive for purposes

other than running the OS. The only small drawback is the startup time it

takes for the CD or DVD to initially load the OS into memory.

Live USBs

Live USBs are a

variant on the Live CD/DVD concept. In this case you use a USB memory

stick, flash drive, or USB external disk drive to boot and run the

operating system.

Like live CD and DVDs, live USBs are portable. You can boot an

OS once this way to try it out, or you can work this way

regularly. USBs offer writeable, persistent storage. Memory sticks have

no moving parts so

they have better access times than optical discs.

The big

downside to USBs is that many older systems won’t boot from

them. This is a BIOS

limitation. Circumvent it by using a boot

manager that boots the computer from a device your BIOS supports, then

immediately switches

control to the USB device. PLoP is one free boot manager. Another potential downside to USB booting is shortened lifespans

for USB memory, due to its constant use as the OS resident media.

Virtual Machines

Desktop virtualization

has matured in the past five years. Hardware

technologies like Intel’s VT-x

and AMD’s AMD-V

underlie and improve it. These were introduced in 2005 and 2006, respectively.

This chart lists

and compares platform virtualization software. Oracle VM VirtualBox

is probably the most popular free offering for personal use. Once owned

by Sun

Microsystems, the product was taken over by Oracle with their

acquisition of Sun in January 2010.

VirtualBox installs under an

existing host operating system,

then creates one or more virtual

machines in which various guest

operating systems

run. The possible host includes most popular operating systems, such as


7, Vista, Windows XP, Linux, Mac OS X, Solaris, and some BSD versions.


include all

the host systems plus even some lesser known contenders, like Haiku,

OS/2 Warp, Syllable, SkyOS, ReactOS, and the rest of the Windows and

BSD versions.

VirtualBox offers all the advantages of platform

virtualization. These include

the abilities to:

  • Securely run more than one OS at a time
  • Flip between the systems as you like
  • Start, stop, and pause the systems independently
  • Communicate between systems through several mechanisms
  • Dynamically allocate and switch processor and memory resources

    among the systems

  • Make an image of a current system state for backup/restore by taking a snapshot

VirtualBox does not require CPU-based virtualization support (VT-x

or AMD-V). But it does require the cumulative resources to run all the

OS’s you want to at one time. Thus it may not be an option for

some refurbished computers. If your computer supports it,

virtualization is a great way to go. Get

started with VirtualBox with tutorials from here

and here. Visit the official VirtualBox website here.

Co-Installing to Disk

If virtualization and Live CDs don’t appeal, you can

always go the traditional route and install more than one operating

system to disk.

Assuming the computer already runs Windows and you want

to co-install a Linux distro, the typical procedure is:

  1. Boot the Live Linux CD for the product you want to install
  2. Shrink the Windows partition to create sufficient space for the

    Linux install

  3. Create a new Linux partition in the newly-released space
  4. Optionally create a swap partition for Linux virtual memory
  5. Install Linux into the new Linux partition
  6. Install a tool like GRUB or LILO to display an OS selection menu

    upon system start-up

  7. Reboot and verify the OS selection menu and the new Linux install

Let’s walk through the steps.

First you boot a Live CD or DVD for the Linux you want to

install. This allows you to test and ensure the distro drives all your

computer’s devices and works the way you want — before you install anything. It also creates a

working environment from which you can perform

the subsequent steps. Most distros provide the partition

management and boot control tools you’ll need. Ubuntu and Puppy

Linux, for

example, both offer Live CDs that bundle the GParted partition

manager and the GRUB boot-selection


Assuming the computer came with a single disk with Windows installed,

you’ll probably need to shrink the Windows partition to make room for

Linux. How much space Linux requires depends on the distribution. A

small Linux like Puppy installs easily in a gigabyte or even

500 megabytes, while a full-sized Linux like Ubuntu typically requires

anywhere from three to eight gigabytes.

Beyond the operating system partition, you may also want to create a swap partition.

Linux uses this disk space for extra memory (or virtual memory)

if real memory runs out. Do you need a swap partition? Think of it this

way. What is the maximum size of memory you’ll require for the Linux

operating system plus the maximum number of applications you’ll have

open at one time? If this amount is greater than the size of real

memory, you need a swap partition to make up the difference.

Since users run different distros and use their computers in

different ways, it’s not possible to devise an all purpose

rule-of-thumb for sizing swap space. Running typical home and office applications, for

example, I never use the swap if the computer has at least 1 gigabyte

of RAM. Specialized applications change this recommendation. For

example, when I do database testing and research, even computers with

several gigabytes need swap space.


next step to installing Linux on a Windows computer is to ensure you

have some free disk space on which to install Linux. You may have to

reduce the size of the Windows partition on a single-disk Windows

system because, by default, many

vendors still pre-install Windows

to consume the entire disk.

It’s wise to run a Windows Disk Check prior to shrinking the Windows

partition to ensure file system integrity. Then use the GParted Linux tool to shrink the Windows partition.

You do not need to run the

Windows defragmentation utility prior to this operation — contrary to

what you might read elsewhere on the web. GParted successfully shrinks NTFS partitions regardless of whether they have been defragmented.

At this point you have a target partition ready into which to

install Linux, and optionally, a swap partition. Now you can install

Linux. Most

Live Linuxes have an “install icon” on their desktop that you click to

start the


process. Although I’ve discussed getting the partitions ready prior to

running this install tool, many Linuxes (such as Ubuntu),

bundle the

partition management tool as a step within their standard install


In other words, you can either manually do the partition management in

advance, or do it while you run the Linux distro installer.

Here’s an example of GParted in action. This screenshot shows what you

can do with multiple operating systems even on an old refurbished test machine with two tiny 40G disks. This

system has four operating systems

installed on its primary drive. This includes a 13.67 gigabyte NTFS

partition with the original

Windows XP SP3 install. Then there are Linux partitions for Ubuntu,

Puppy, and Vector Linux. The

single Swap partition of about 510 M


whichever Linux runs. A second 40G disk drive (not shown), contains

three more Linux distros, three backup partitions, and a BSD variant. Quite a lot of action for an old computer!

GParted Sample Screen

An Example GParted Screen

The first line in the above display is a FAT32 partition on which all


data resides. Storing user data apart from any of the

operating system partitions is wise because it segregates data from the

operating systems. This makes it easy to identify and back up user

data. Moreover, the user data remains

unaffected regardless of what changes you make to any of the

operating systems or their partitions. Should an “OS disaster” occur

it’s unlikely that data on its own partition will be affected.


is unfortunate that many

consumer computers by default still store user data on a single

Windows partition that consumes the entire disk. This practice is a

hold-over from the days when

disks were smaller and it doesn’t leverage the advantages of


larger disks. With big SATA drives it makes

much more sense to segregate data and OS partitions. I know some people

who even separate out certain kinds of data files into their own

partitions. For example, you might have a “multimedia partition” for

photographs, music, or videos. This makes it easy to separately manage

large data

files. Or segregate your work from your play by creating an “office

partition” for office suite documents. Easy partitioning makes it

possible to organize your system in the way that works best for you.

When adding Linux to a Windows computer, you’ll install a boot manager,

such as GRUB or LILO.

In Ubuntu and Puppy,

this is an option in the last step in the install process. GRUB takes

over the master

boot record or

MBR on the computer’s disk and inserts code that displays a menu

to select any of

the resident operating systems when you start the computer.

Don’t worry

about your existing Windows being bootable. GRUB is very good at automatically

detecting any operating systems already on your hard disk. It generates

the necessary code to make them boot-time selections. So GRUB will find

Windows and automatically place it in your new boot-time OS selection


When the install is complete, reboot your computer and you’ll see GRUB’s menu with options to enter either

Windows or Linux. Try both out to ensure everything works

ok, and you’re done. Voila! Multiple OS’s on your computer.

Once you’ve gotten everything working, you might want to make

the boot-time OS selection menu more readable. If you used GRUB,

just edit the

file menu.lst in the /boot/grub folder. (Save the original menu.lst

file first as a backup!) If your Linux distro uses the newer GRUB 2,

well, there are many advantages to this new boot loader, but easy

changes to the boot menu is not among them. See this excellent tutorial

for help. It’s too bad that GRUB 2 is a step backwards for ease of use,

especially since it would have been easy for the product to use a menu.lst file if present and convert it to the required internal code.


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