mirror of https://github.com/tLDP/LDP
413 lines
18 KiB
Plaintext
413 lines
18 KiB
Plaintext
<!doctype linuxdoc system>
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<article>
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<title> Managing Multiple Operating Systems HOWTO
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</title>
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<author> Robert W. Schultz
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</author>
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<date> v0.4, 17 Feb 2000
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</date>
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<abstract>This HOWTO covers the procedures for using removable hard disks
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to install and manage multiple alternative operating systems while leaving
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a single fixed disk to permanently house and protect the primary operating
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system. It is very scalable and offers a good degree of protection to
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and a stable disk environment for the primary operating system.
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</abstract>
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<toc>
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<sect>Introduction
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<sect1> Copyright
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<p>
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Copyright (c) 2000 by Robert W. Schultz.
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<!-- license.H begin -->
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Please freely copy and distribute (sell or give away) this document in
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any format. It's requested that corrections and/or comments be forwarded to
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the document maintainer. You may create a derivative work and distribute
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it provided that you:
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1.Send your derivative work (in the most suitable format such as sgml)
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to the LDP (Linux Documentation Project) or the like for posting on the
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Internet. If not the LDP, then let the LDP know where it is available.
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2.License the derivative work with this same license or use GPL. Include
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a copyright notice and at least a pointer to the license used.
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3.Give due credit to previous authors and major contributors.
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If you're considering making a derived work other than a translation,
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it's requested that you discuss your plans with the current maintainer.
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<!-- copyright.H end -->
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<sect1> New Versions of this HOWTO
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<p> New versions of the Managing Multiple Operating Systems HOWTO will
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be available to browse and/or download at LDP mirror sites. For a list
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of mirror sites see:
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<url url="http://metalab.unc.edu/LDP/mirrors.html">.
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Various formats are available. If you only want to quickly check the
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date of the latest version look at
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<url url="http://www.linuxdoc.org/HOWTO/MultiOS-HOWTO.html">
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and compare it to this version: v0.4, 17 February 2000
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<sect1>Feedback
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<p> Please send any questions, comments, or suggestions to <tt><htmlurl
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url="mailto:rwschul@smart.net"> (Robert W. Schultz)</tt>. I am very
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willing to help others with problems directly relating to this HOWTO
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and will entertain any suggestions for changes/modifications and/or
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improvements. However, having set up my system to my satisfaction,
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this HOWTO won't be significantly improved without reader input.
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<sect> Purpose and goals:
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<p>The purpose of this HOWTO is to describe a methodology for managing
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multiple operating systems on a single computer system. It is intended
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for Linux users who have a basic familiarity with both Linux and LILO
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installations. Nothing here is terribly complex however, considering
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the amount of time it takes to install some operating systems it can be
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relatively time consuming.
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<p>It is different from other methods in that it doesn't require multiple
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operating systems on the boot disk. Instead it uses a fixed internal disk
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containing a single primary operating system and a selection of removable
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disks with one or more operating systems installed on each of them.
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If you absolutely have to have two, three, or four different operating
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systems on a single disk and are trying to get them to behave with each
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other, this HOWTO is not for you.
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<p>Its specific goals are:
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<p>* - A primary/operational disk that once configured and installed
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is rarely changed. This includes not having to repartition or
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otherwise modify the disk it resides on.
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<p>* - Easy selection of multiple alternative operating systems at boot
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time without having to go through more than one or two menu selections.
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<p>* - No need to modify the BIOS, LILO, or any other configuration to
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access an O/S once it is installed.
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<p>* - Easy addition/removal of operating systems depending on
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requirements at the moment.
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<p>* - Inexpensive and scalable to allow for an increasing number of
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operating systems and versions as time goes on.
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<p>I think I succeeded admirably in the first three of these requirements.
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You can form your own opinions on the last two.
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<sect> Background: <p>Even though Linux is becoming much more user
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friendly and widely accepted, most of us still need access to other
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operating systems. I use Linux about 75% of the time but I still
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need access to Win 9x for those few applications that I haven't found
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acceptable alternatives for in Linux. My wife uses MS Office at work and
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wants to have access to it at home. Other people want to have access to
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alternative O/S just for fun, training, or to keep current in their job.
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<p>I tend to treat new O/S's as you would a game; I actually don't do
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anything productive with them but installing and learning how to control
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them is just as challenging and interesting to me as Quake or SimCity.
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Further, being a Computer Scientist, it keeps me current on evolving
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technology and has helped me solve a multitude of problems at work.
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At any rate, for new Linux users, computer professionals, and those just
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trying to migrate from one operating system to another, I believe using
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multiple operating systems is the norm rather than the exception.
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<sect> System requirements:
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<p>BIOS - Any bios that allows automatic identification of disk drive
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geometry and allows you to select the sequence of devices to boot from
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should work. I successfully built systems based on both PhoenixBIOS
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4.0 and AMI Plug and Play Flash BIOS.
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<p>DISKS - One fixed internal disk dedicated to Linux. (first disk)
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One Removable drive enclosure, with any number of drives. (second disk)
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<p>Since a lot of this HOWTO has to do with disks, from now on I will
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generally use the terms "first disk" and "second disk". The first disk is the
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one initially accessed when the machine is turned on, commonly known as the
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boot disk. It has LILO installed in the MBR and is dedicated to a single
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operating system, specifically Linux. The second disk is a removable disk
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that contains one or more alternative operating systems which may or may not
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have a boot loader in the MBR or elsewhere.
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<p>There are no other hardware/firmware requirements. Any other
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requirements would be dictated by the specific O/S. For instance, even
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though you could install it, Solaris 7 is not going to run well on an
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old 90MHz machine! The configuration and methodology described here
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should however work equally well regardless of the CPU speed or other
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installed peripherals.
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<p>Operating Systems - I have tested this process with Linux (Redhat
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and Suse), Solaris 7, BeOS, Win 98 and even MSDOS 6.22. I see no reason
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why it wouldn't work with Win 95, O/S 2, or FreeBSD. I am not familiar
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with Windows NT or 2000 so I don't know how they would react to this
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kind of setup.
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<p>Boot loader - I used LILO on the first disk and BeOS bootman on the
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second disks. I used LILO on the first disk because it was the only
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boot loader that allowed me to select the MBR on the second disk as an
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acceptable boot partition. Any relatively robust boot loader should
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work on the second disk.
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<sect> How it works (a scenario):
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<p>Prior to ignition, I insert a disk, preloaded with an operating system
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in the removable drive. When I turn on the machine, I am presented at the
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LILO prompt (by pressing <tab>) with "Linux" and "Disk2" as options.
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Linux is the default and would automatically boot if I did nothing.
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When selected, Disk2 either boots directly into the single O/S stored on
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the second disk or presents me with a second boot menu if there is more
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than one O/S on that disk. If I power down, replace the second disk with
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another and power back up, I still get the initial Linux/Disk 2 menu and,
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if I select Disk2, a new menu appropriate to the newly inserted disk.
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Once installed, I never have to modify the LILO configuration on the
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first disk, I never have to change BIOS setting to boot from the second
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disk and I never have to go through more than two menu selections to
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get my selected O/S up and running.
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<sect> The installation:
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<p>There are three distinct parts to the installation, first building
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the primary O/S on its own dedicated drive. Second, building a second
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disk with whatever alternative O/S you selected. Finally, reconfiguring
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the BIOS and LILO to support both disks.
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<sect1> Installing the primary operating system
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<p>Installation of the primary/operational O/S is fairly straight forward.
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Treat the system as if it were a single drive system dedicated to Linux.
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Refer to the documentation that came with your distribution or see
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<url url="http://www.linuxdoc.org/HOWTO/Installation-HOWTO.html">
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for details on installing Linux.
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<p> Because this is ultimately a multiple disk installation, there a few
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steps that need to be taken to trick the install routines into thinking
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that it is, during the installation process, a single disk system.
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<p> First, Remove the removable Hard Drive and make sure the remaining
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drive is identified in the BIOS as the secondary boot device (after the
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floppy). The operating system install program should only see one disk,
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the one you are going to install to. That way, there is no question
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as to where it will be installed. Also, it will install everything
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appropriate to a single disk system.
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<p>When asked, tell the install program to use the entire disk for
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your operating system. I accepted the default RedHat partitioning and
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installed the generic LILO on the MBR.
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<p> Once the installation is complete, shutdown and reboot to confirm
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that your system works properly. At this point you should have a fully
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functional machine that boots directly into Linux.
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<sect1> Installing alternative operating systems
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<p> Now that you have a fully functional system, you can move on to
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building a second disk with your alternative operating systems.
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<p>Select an operating system or two for installation on the second disk.
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I decided on, for no good reason, Windows 98 and BeOS for my initial
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test case. I partitioned an 8GB drive into two 4GB primary partitions
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and installed Windows 98 in the first partition and BeOS in the second.
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<p>Do the same things with this install that you did with the first.
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Disable the first disk in the BIOS so that this installer will not
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even see it. This is very important. If you can physically remove or
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disconnect the first disk, do it! This will protect your primary system
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from any errors on your part or overly greedy operating systems that
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want to take over all the disks they see during the second installation.
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If at some time in the future you decide to create another removable
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disk make sure and repeat this step.
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<p>Once this is done install your chosen operating systems as if you
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were installing them on a single drive system.
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<p> If you are only installing one operating system on the second disk,
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just plug in the installation disk and let it do its thing. Windows 95
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or 98 or just about any other operating system, including a second Linux
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should install just fine this way. Allow Windows 9x to write to the MBR. If installing Linux, select MBR as the location to install LILO.
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<p> I decided to install two operating systems on the second disk so
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that I could confirm the functionality of cascading boot loaders.
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<p>I first installed Windows 98 because it automatically overwrites the
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MBR and would have overwritten any boot loader code I eventually placed
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there. Next, I installed BeOS in the second partition and ran bootman,
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the BeOS boot loader. With it I built a boot menu for the second disk
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and intentionally overwrote the Windows 98 MBR.
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<p>Bootman was not essential, I could have used any MBR based boot
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loader but it was available and it works quite will.
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<p>Reboot frequently to make sure that everything works properly as
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a single disk system. I rebooted after each O/S installation to make
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sure it worked properly and also to make sure that the boot loader menu
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worked properly.
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<sect1> Final BIOS and LILO configuration:
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<p>Next, reconfigure the BIOS so that it again recognizes the first disk
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(physically reconnect it if you disconnected it earlier) as the boot
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disk and so that it also recognizes the second disk. How to do this is
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very system specific and dependent on your BIOS and whether you have a
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SCSI/IDE or IDE/IDE setup. I haven't tried a SCSI/SCSI setup because
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SCSI disks and removable frames are significantly more expensive than
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IDE disks and frames. I wanted performance for my primary O/S but could
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accept cheap on the other ones.
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<p>Make sure and set the second disk type to "Auto" or "Automatic".
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This will force the BIOS to dynamically determine the disk type at
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boot time. I have been able to successfully use an ancient 512MB
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disk, a 4GB, an 8GB, and even a 100MB IDE Zip disk as the second disk.
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All recognized automatically by the BIOS.
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<p>Reboot the system and get back to Linux. At this point, even though
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there are at least two operating systems installed, this LILO only knows
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about the original Linux and should boot to it automatically. Watch the
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boot process and you should see a message about automatically identifying
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a disk. Once booted, check dmesg to make sure Linux recognized the
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second disk.
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<p>Once this is done, you need to reconfigure LILO on the first disk
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to make it aware of the second disk. Here are two different lilo.conf
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files, one for a SCSI/IDE and another for an IDE/IDE system. Each has
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some strengths and weaknesses...
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<verb>
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# lilo.conf file for an internal SCSI disk and a removable disk
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# configured as a master on the primary IDE connection
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disk = /dev/sda # These four lines are necessary
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bios = 0x80 # to get the SCSI disk re-mapped as
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disk = /dev/hda # the primary drive even though it
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bios = 0x81 # is selected in the BIOS as the
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# boot device. This might be a BIOS
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# specific problem.
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# Without them you get the following errors from LILO:
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#
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# LILO version 21, Copyright 1992-1998 Werner Almesberger
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#
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# ading boot sector from /dev/sda
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# Warning: /dev/sda is not on the first disk
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# And LILO either hangs at LI or repeats endless "01 "'s across the screen
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boot=/dev/sda
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map=/boot/map
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install=/boot/boot.b
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prompt
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timeout=50
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image=/boot/vmlinuz-2.2.12-20smp
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label=Linux
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root=/dev/sda1
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initrd=/boot/initrd-2.2.12-20smp.img
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read-only
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other = /dev/hda
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# other = /dev/hda is the key element. Instead of redirecting lilo to
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# a specific partition, it redirects it to the MBR on the second disk.
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# that way, LILO doesn't have to know anything about the second disk and
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# we can replace it with another because LILO always goes to the same place
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# regardless of which specific disk is installed. LILO was the only boot
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# loader I found that would do this.
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label = Disk2
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map-drive = 0x80
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to = 0x81
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map-drive = 0x81
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to = 0x80
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# The map-drive lines are necessary to make the second disk think it is
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# actually the boot disk.
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# lilo.conf file for a system with two IDE drives. Both are masters,
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# /dev/hda on the primary connector and /dev/hdc on the secondary.
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# /dev/hdb is a CDROM slave on the primary IDE connector.
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# disk = /dev/hda # These lines are not necessary for the
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# bios = 0x80 # IDE/IDE installation because the BIOS
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# disk = /dev/hdc # already knows what order they are in
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# bios = 0x81
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boot=/dev/hda
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map=/boot/map
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install=/boot/boot.b
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prompt
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timeout=50
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image=/boot/vmlinuz-2.2.5-15
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label=linux
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root=/dev/hda4
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read-only
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other = /dev/hdc
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# other = /dev/hdc is again the key. This just redirects LILO to the
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# MBR of the second disk. Whatever is there gets control.
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label = Disk2
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map-drive = 0x80
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to = 0x81
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map-drive = 0x81
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to = 0x80
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</verb>
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<p>The /dev, boot, map and image entries are system specific and yours
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will probably be different that mine. The entries in your initial
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/etc/lilo.conf file should give you an accurate guide for your system.
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I copied the "Linux" entry from the original install generated lilo.conf
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file directly into the new lilo.conf. This should allow you to boot into
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"Linux" and modify your lilo.conf even if the "Disk2" entry fails totally.
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<p>Finally, run lilo -vvv to make sure it agrees with everything you
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are trying to do.
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<sect> Cost and gotcha's:
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<sect1> Cost:
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<p>I found a Frame and 1 drawer removable drive mount for $20.00.
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It is the "SNT MOBILE RACK". Disks didn't cost me anything because I
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had several old or small IDE drives around from upgrades etc. Even if
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you have to buy them, 2GB IDE drives are cheap.
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<sect1> Gotcha's
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<p>1. Once you decide whether your removable drive is going to be a
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master or slave, make sure and jumper it properly before securing it
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in its case. If you forget this step it can take quit a while to trace
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booting problems back to an improper jumper setting.
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<p>2. Make sure that O/S installation routines can ONLY see the drive
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they are installing to. RedHat refused to let me install LILO to the
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SCSI MBR if it could see the IDE drive. So, to install to an internal
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SCSI drive, I had to physically remove the IDE. To install to the IDE,
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I had to disable SCSI support in the BIOS.
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<p>3. If an O/S installation routine tells you it is going to repartition
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ALL your drives and overwrite EVERYTHING believe it.
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<p>4. It is very easy to install an IDE cable backwards.
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<p>5. I only tested an IDE master/master set up. I am not sure how a
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master/slave would work.
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<p>6. Installing the removable disk frame does require opening up the
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computer case. If you are uncomfortable with this get a friend to help.
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<p>7. If you set the removable disk to a specific disk type in the BIOS
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it will work fine until you replace it with another disk of a different
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type. Then you will get errors or warnings and the system might not boot.
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<p>8. Plan everything in advance.
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<p>9. With a quick change to the BIOS, the second disk becomes your
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boot disk. This means that you can have a fully functional O/S available
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as your emergency/recovery disk.
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</article>
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