682 lines
26 KiB
Text
682 lines
26 KiB
Text
<!-- $Id: article.sgml,v 1.4 1998-11-30 23:14:55 billf Exp $ -->
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<!DOCTYPE BOOK PUBLIC "-//Davenport//DTD DocBook V3.0//EN">
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<book>
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<bookinfo>
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<bookbiblio>
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<title>Installing and Using FreeBSD With Other Operating Systems</title>
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<authorgroup>
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<author>
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<firstname>Jay</firstname>
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<surname>Richmond</surname>
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<affiliation>
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<address>
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<email>jayrich@sysc.com</email>
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</address>
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</affiliation>
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</author>
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</authorgroup>
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<pubdate>6 August 1996</pubdate>
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<abstract><para>This document discusses how to make FreeBSD coexist
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nicely with other popular operating systems such as Linux, MS-DOS,
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OS/2, and Windows 95. Special thanks to: Annelise Anderson
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<email>andrsn@stanford.edu</email>, Randall Hopper
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<email>rhh@ct.picker.com</email>, and Jordan K. Hubbard
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<email>jkh@time.cdrom.com</email></para></abstract>
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</bookbiblio>
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</bookinfo>
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<chapter>
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<title>Overview</title>
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<para>Most people can't fit these operating systems together
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comfortably without having a larger hard disk, so special
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information on large EIDE drives is included. Because there are so
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many combinations of possible operating systems and hard disk
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configurations, the <xref linkend="ch5"> section may be of the most use
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to you. It contains descriptions of specific working computer setups
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that use multiple operating systems.</para>
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<para>This document assumes that you have already made room on your
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hard disk for an additional operating system. Any time you
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repartition your hard drive, you run the risk of destroying the data
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on the original partitions. However, if your hard drive is completely
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occupied by DOS, you might find the FIPS utility (included on the
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FreeBSD CD-ROM in the <filename>\TOOLS</filename> directory or via
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<ulink URL="ftp://ftp.freebsd.org/pub/FreeBSD/tools">ftp</ulink>)
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useful. It lets you repartition your hard disk without destroying the
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data already on it. There is also a commercial program available
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called Partition Magic, which lets you size and delete partitions
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without consequence.</para>
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</chapter>
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<chapter id="ch2">
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<title>Overview of Boot Managers</title>
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<para>These are just brief descriptions of some of the different boot
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managers you may encounter. Depending on your computer setup, you may
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find it useful to use more than one of them on the same
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system.</para>
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<variablelist>
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<varlistentry>
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<term>Boot Easy</term>
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<listitem>
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<para>This is the default boot manager used with FreeBSD. It has the
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ability to boot most anything, including BSD, OS/2 (HPFS), Windows 95
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(FAT and FAT32), and Linux. Partitions are selected with the
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function keys.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>OS/2 Boot Manager</term>
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<listitem>
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<para>This will boot FAT, HPFS, FFS (FreeBSD), and EXT2
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(Linux). It will also boot FAT32 partitions. Partitions are
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selected using arrow keys. The OS/2 Boot Manager is the only one to
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use its own separate partition, unlike the others which use the
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master boot record (MBR). Therefore, it must be installed below the
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1024th cylinder to avoid booting problems. It can boot Linux using
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LILO when it is part of the boot sector, not the MBR. Go to <ulink
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URL="http://www.linuxresources.com/LDP/HOWTO/HOWTO-INDEX.html">Linux HOWTOs</ulink>
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on the World Wide Web for more information on booting Linux with
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OS/2's boot manager.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>OS-BS</term>
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<listitem> <para>This is an alternative to Boot Easy. It gives you
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more control over the booting process, with the ability to set the
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default partition to boot and the booting timeout. The beta version
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of this programs allows you to boot by selecting the OS with your
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arrow keys. It is included on the FreeBSD CD in the
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<filename>\TOOLS</filename> directory, and via <ulink
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URL="ftp://ftp.freebsd.org/pub/FreeBSD/tools">ftp</ulink>.</para>
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</listitem> </varlistentry>
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<varlistentry>
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<term>LILO, or LInux LOader</term>
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<listitem>
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<para>This is a limited boot manager. Will boot FreeBSD, though some
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customization work is required in the LILO configuration file.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<note id="fat32"><title>About FAT32</title><para>FAT32 is the replacement to
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the FAT filesystem included in Microsoft's OEM SR2 Beta release,
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which is expected to utilitized on computers pre-loaded with Windows
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95 towards the end of 1996. It converts the normal FAT file system
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and allows you to use smaller cluster sizes for larger hard drives.
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FAT32 also modifies the traditional FAT boot sector and allocation
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table, making it incompatible with some boot managers.</para></note>
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</chapter>
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<chapter id="ch3">
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<title>A Typical Installation</title>
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<para>Let's say I have two large EIDE hard drives, and I want to
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install FreeBSD, Linux, and Windows 95 on them.</para>
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<para>Here's how I might do it using these hard disks:
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<itemizedlist>
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<listitem>
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<para><filename>/dev/wd0</> (first physical hard disk)</para>
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</listitem>
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<listitem>
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<para><filename>/dev/wd1</> (second hard disk)</para>
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</listitem>
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</itemizedlist>
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</para>
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<para>Both disks have 1416 cylinders.</para>
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<procedure>
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<step><para>I boot from a MS-DOS or Windows 95 boot disk that
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contains the <filename>FDISK.EXE</> utility and make a small 50 meg
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primary partition (35-40 for Windows 95, plus a little breathing
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room) on the first disk. Also create a larger partition on the
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second hard disk for my Windows applications and data.</para></step>
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<step><para>I reboot and install Windows 95 (easier said than done)
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on the <filename>C:</> partition.</para> </step>
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<step><para>The next thing I do is install Linux. I'm not sure about
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all the distributions of Linux, but slackware includes LILO (see
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<xref linkend="ch2">). When I am partitioning out my hard disk with
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Linux <command>fdisk</command>, I would put all of Linux on the first
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drive (maybe 300 megs for a nice root partition and some swap
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space).</para></step>
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<step><para>After I install Linux, and are prompted about installing
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LILO, make SURE that I install it on the boot sector of my root
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Linux partition, not in the MBR (master boot record).</para></step>
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<step><para>The remaining hard disk space can go to FreeBSD. I also
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make sure that my FreeBSD root slice does not go beyond the 1024th
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cylinder. (The 1024th cylinder is 528 megs into the disk with our
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hypothetical 720MB disks). I will use the rest of the hard drive
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(about 270 megs) for the <filename>/usr</> and <filename>/</> slices
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if I wish. The rest of the second hard disk (size depends on the
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amount of my Windows application/data partition that I created in
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step 1 can go to the <filename>/usr/src</> slice and swap
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space.</para></step>
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<step><para>When viewed with the Windows 95 <command>fdisk</> utility, my hard drives
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should now look something like this:
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<screen>
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---------------------------------------------------------------------
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Display Partition Information
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Current fixed disk drive: 1
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Partition Status Type Volume_Label Mbytes System Usage
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C: 1 A PRI DOS 50 FAT** 7%
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2 A Non-DOS (Linux) 300 43%
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Total disk space is 696 Mbytes (1 Mbyte = 1048576 bytes)
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Press Esc to continue
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---------------------------------------------------------------------
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Display Partition Information
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Current fixed disk drive: 2
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Partition Status Type Volume_Label Mbytes System Usage
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D: 1 A PRI DOS 420 FAT** 60%
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Total disk space is 696 Mbytes (1 Mbyte = 1048576 bytes)
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Press Esc to continue
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---------------------------------------------------------------------
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</screen>
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** May say FAT16 or FAT32 if you are using the OEM SR2 update.
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See <xref linkend="ch2">).</para></step>
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<step><para>Install FreeBSD. I make sure to boot with my first hard
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disk set at <quote>NORMAL</> in the BIOS. If it is not, I'll have
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the enter my true disk geometry at boot time (to get this, boot
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Windows 95 and consult Microsoft Diagnostics (<filename>MSD.EXE</>),
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or check your BIOS) with the parameter <literal>hd0=1416,16,63</>
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where <replaceable>1416</> is the number of cylinders on my hard
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disk, <replaceable>16</> is the number of heads per track, and
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<replaceable>63</> is the number of sectors per track on the
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drive.</para></step>
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<step><para>When partitioning out the hard disk, I make sure to install
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Boot Easy on the first disk. I don't worry about the second disk,
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nothing is booting off of it.</para></step>
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<step><para>When I reboot, Boot Easy should recognize my three
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bootable partitions as DOS (Windows 95), Linux, and BSD
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(FreeBSD).</para></step>
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</procedure>
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</chapter>
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<chapter id="ch4">
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<title>Special Considerations</title>
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<para>Most operating systems are very picky about where and how they are
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placed on the hard disk. Windows 95 and DOS need to be on the first
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primary partitiin on the first hard disk. OS/2 is the exception. It
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can be installed on the first or second disk in a primary or extended
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partition. If you are not sure, keep the beginning of the bootable
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partitions below the 1024th cylinder.</para>
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<para>If you install Windows 95 on an existing BSD system, it will
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<quote>destroy</> the MBR, and you will have to reinstall your
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previous boot manager. Boot Easy can be reinstalled by using the
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BOOTINST.EXE utility included in the \TOOLS directory on the CD-ROM,
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and via <ulink
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URL="ftp://ftp.freebsd.org/pub/FreeBSD/tools">ftp</ulink>. You can
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also re-start the installation process and go to the partition
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editor. From there, mark the FreeBSD partition as bootable,
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select Boot Manager, and then type W to (W)rite out the information
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to the MBR. You can now reboot, and Boot Easy should then
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recognize Windows 95 as DOS.</para>
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<para>Please keep in mind that OS/2 can read FAT and HPFS partitions,
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but not FFS (FreeBSD) or EXT2 (Linux) partitions. Likewise, Windows
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95 can only read and write to FAT and FAT32 (see <xref
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linkend="ch2">) partitions. FreeBSD can read most file systems, but
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currently cannot read HPFS partitions. Linux can read HPFS
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partitions, but can't write to them. Recent versions of the Linux
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kernel (2.x) can read and write to Windows 95 VFAT partitions (VFAT
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is what gives Windows 95 long file names - it's pretty much the same
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as FAT). Linux can read and write to most file systems. Got that?
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I hope so.</para>
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</chapter>
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<chapter id="ch5">
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<title>Examples</title>
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<para><emphasis>(section needs work, please send your example to
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<email>jayrich@sysc.com</email>)</emphasis>.</para>
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<para>FreeBSD+Win95: If you installed FreeBSD after Windows 95, you
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should see <literal>DOS</> on the Boot Easy menu. This is Windows
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95. If you installed Windows 95 after FreeBSD, read <xref
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linkend="ch4"> above. As long as your hard disk does not have 1024
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cylinders you should not have a problem booting. If one of your
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partitions goes beyond the 1024th cylinder however, and you get
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messages like <errorname>invalid system disk</> under DOS (Windows 95)
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and FreeBSD will not boot, try looking for a setting in your BIOS
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called <quote>> 1024 cylinder support</> or <quote>NORMAL/LBA</>
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mode. DOS may need LBA (Logical Block Addressing) in order to boot
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correctly. If the idea of switching BIOS settings every time you
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boot up doesn't appeal to you, you can boot FreeBSD through DOS via
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the <filename>FBSDBOOT.EXE</> utility on the CD (It should find your
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FreeBSD partition and boot it.)</para>
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<para>FreeBSD+OS/2+Win95: Nothing new here. OS/2's boot manger
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can boot all of these operating systems, so that shouldn't be a
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problem.</para>
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<para>FreeBSD+Linux: You can also use Boot Easy to boot both operating
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systems.</para>
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<para>FreeBSD+Linux+Win95: (see <xref linkend="ch3">)</para>
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</chapter>
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<chapter id="sources">
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<title>Other Sources of Help</title>
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<para>There are many <ulink
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URL="http://www.linuxresources.com/LDP/HOWTO/HOWTO-INDEX.html">Linux HOW-TOs</ulink> that
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deal with multiple operating systems on the same hard disk.</para>
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<para>The <ulink
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URL="http://www.linuxresources.com/LDP/HOWTO/mini/Linux+DOS+Win95+OS2.html">Linux+DOS+Win95+OS2
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mini-HOWTO</ulink> offers help on configuring the OS/2 boot manager, and the
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<ulink
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URL="http://www.linuxresources.com/LDP/HOWTO/mini/Linux+FreeBSD.html">Linux+FreeBSD
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mini-HOWTO</ulink> might be interesting as well. The <ulink
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URL="http://www.in.net/~jkatz/win95/Linux-HOWTO.html">Linux-HOWTO</ulink> is
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also helpful.</para>
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<para>The <ulink
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URL="http://www.dorsai.org/~dcl/publications/NTLDR_Hacking">NT Loader
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Hacking Guide</ulink> provides good information on multibooting
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Windows NT, '95, and DOS with other operating systems.</para>
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<para>And Hale Landis's "How It Works" document pack contains some good info
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on all sorts of disk geometry and booting related topics. Here are a few
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links that might help you find it: <ulink URL="ftp://fission.dt.wdc.com/pub/otherdocs/pc_systems/how_it_works/allhiw.zip">ftp://fission.dt.wdc.com/pub/otherdocs/pc_systems/how_it_works/allhiw.zip</ulink>,
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<ulink URL="http://web.idirect.com/~frank/">http://www.cs.yorku.ca/People/frank/docs/</ulink>.</para>
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<para>Finally, don't overlook FreeBSD's kernel documentation on the booting
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procedure, available in the kernel source distribution (it unpacks to
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<ulink URL="file:/usr/src/sys/i386/boot/biosboot/README.386BSD">file:/usr/src/sys/i386/boot/biosboot/README.386BSD</ulink>.</para>
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</chapter>
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<chapter>
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<title>Technical Details</title>
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<para><emphasis>(Contributed by Randall Hopper,
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<email>rhh@ct.picker.com</email>)</emphasis></para>
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<para>This section attempts to give you enough basic information
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about your hard disks and the disk booting process so that you can
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troubleshoot most problems you might encounter when getting set up to
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boot several operating systems. It starts in pretty basic terms, so
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you may want to skim down in this section until it begins to look
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unfamiliar and then start reading.</para>
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<sect1>
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<title>Disk Primer</title>
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<para>Three fundamental terms are used to describe the location of
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data on your hard disk: Cylinders, Heads, and Sectors. It's not
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particularly important to know what these terms relate to except to
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know that, together, they identify where data is physically on your
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disk.</para>
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<para>Your disk has a particular number of cylinders, number of
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heads, and number of sectors per cylinder-head (a cylinder-head also
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known nown as a track). Collectively this information defines the
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"physical disk geometry" for your hard disk. There are typically 512
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bytes per sector, and 63 sectors per track, with the number of
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cylinders and heads varying widely from disk to disk. Thus you can
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figure the number of bytes of data that'll fit on your own disk by
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calculating: <informalexample><para>(# of cylinders) × (#
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heads) × (63 sectors/track) × (512
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bytes/sect)</></informalexample> For example, on my 1.6 Gig Western
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Digital AC31600 EIDE hard disk,that's: <informalexample><para>(3148
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cyl) × (16 heads) × (63 sectors/track) × (512
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bytes/sect)</para></informalexample></para>
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<para>which is 1,624,670,208 bytes, or around 1.6 Gig.</para>
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<para>You can find out the physical disk geometry (number of
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cylinders, heads, and sectors/track counts) for your hard disks using
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ATAID or other programs off the net. Your hard disk probably came
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with this information as well. Be careful though: if you're using
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BIOS LBA (see <xref linkend="limits">), you can't use just any
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program to get the physical geometry. This is because many programs
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(e.g. <filename>MSD.EXE</> or FreeBSD fdisk) don't identify the
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physical disk geometry; they instead report the
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<firstterm>translated geometry</> (virtual numbers from using LBA).
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Stay tuned for what that means.</para>
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<para>One other useful thing about these terms. Given 3
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numbers—a cylinder number, a head number, and a
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sector-within-track number—you identify a specific absolute
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sector (a 512 byte block of data) on your disk. Cylinders and Heads
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are numbered up from 0, and Sectors are numbered up from 1.</para>
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<para>For those that are interested in more technical details,
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information on disk geometry, boot sectors, BIOSes, etc. can be found
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all over the net. Query Lycos, Yahoo, etc. for <literal>boot
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sector</> or <literal>master boot record</>. Among the useful info
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you'll find are Hale Landis's <citetitle>How It Works</> document
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pack. See the <xref linkend="sources"> section for a few pointers to
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this pack.</para>
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<para>Ok, enough terminology. We're talking about booting
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here.</para>
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</sect1>
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<sect1 id="booting">
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<title>The Booting Process</title>
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<para>On the first sector of your disk (Cyl 0, Head 0, Sector 1)
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lives the Master Boot Record (MBR). It contains a map of your disk.
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It identifies up to 4 <firstterm>partitions</>, each of which is a
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contiguous chunk of that disk. FreeBSD calls partitions
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<firstterm>slices</> to avoid confusion with it's own partitions, but
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we won't do that here. Each partition can contain its own operating
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system.</para>
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<para>Each partition entry in the MBR has a <firstterm>Partition
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ID</>, a <firstterm>Start Cylinder/Head/Sector</>, and an
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<firstterm>End Cylinder/Head/Sector</>. The Partition ID tells what
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type of partition it is (what OS) and the Start/End tells where it
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is. <xref linkend="tbl-pid"> lists a smattering of some common
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Partition IDs.</para>
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<table id="tbl-pid">
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<title>Partition IDs</>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>ID (hex)</entry>
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<entry>Description</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>01</entry>
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<entry>Primary DOS12 (12-bit FAT)</entry>
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</row>
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<row>
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<entry>04</entry>
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<entry>Primary DOS16 (16-bit FAT)</entry>
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</row>
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<row>
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<entry>05</entry>
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<entry>Extended DOS</entry>
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</row>
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<row>
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<entry>06</entry>
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<entry>Primary big DOS (> 32MB)</entry>
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</row>
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<row>
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<entry>0A</entry>
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<entry>OS/2</entry>
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</row>
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<row>
|
|
<entry>83</entry>
|
|
<entry>Linux (EXT2FS)</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>A5</entry>
|
|
<entry>FreeBSD, NetBSD, 386BSD (UFS)</entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>Note that not all partitions are bootable (e.g. Extended DOS).
|
|
Some are—some aren't. What makes a partition bootable is the
|
|
configuration of the <firstterm>Partition Boot Sector</> that exists
|
|
at the beginning of each partition.</para>
|
|
|
|
<para>When you configure your favorite boot manager, it looks up the entries
|
|
in the MBR partition tables of all your hard disks and lets you name the
|
|
entries in that list. Then when you boot, the boot manager is invoked by
|
|
special code in the Master Boot Sector of the first probed hard disk on
|
|
your system. It looks at the MBR partition table entry corresponding to
|
|
the partition choice you made, uses the Start Cylinder/Head/Sector
|
|
information for that partition, loads up the Partition Boot Sector for that
|
|
partition, and gives it control. That Boot Sector for the partition itself
|
|
contains enough information to start loading the operating system on that
|
|
partition.</para>
|
|
|
|
<para>One thing we just brushed past that's important to know. All of your
|
|
hard disks have MBRs. However, the one that's important is the one on the
|
|
disk that's first probed by the BIOS. If you have only IDE hard disks, its
|
|
the first IDE disk (e.g. primary disk on first controller). Similarly for
|
|
SCSI only systems. If you have both IDE and SCSI hard disks though, the
|
|
IDE disk is typically probed first by the BIOS, so the first IDE disk is
|
|
the first probed disk. The boot manager you will install will be hooked into
|
|
the MBR on this first probed hard disk that we've just described.</para>
|
|
|
|
</sect1>
|
|
|
|
<sect1 id="limits">
|
|
<title>Booting Limitations and Warnings</title>
|
|
|
|
<para>Now the interesting stuff that you need to watch out for.</para>
|
|
|
|
<sect2>
|
|
<title>The dreaded 1024 cylinder limit and how BIOS LBA helps</title>
|
|
|
|
<para>The first part of the booting process is all done through the
|
|
BIOS, (if that's a new term to you, the BIOS is a software chip on
|
|
your system motherboard which provides startup code for your
|
|
computer). As such, this first part of the process is subject to the
|
|
limitations of the BIOS interface.</para>
|
|
|
|
<para>The BIOS interface used to read the hard disk during this period
|
|
(INT 13H, Subfunction 2) allocates 10 bits to the Cylinder Number, 8
|
|
bits to the Head Number, and 6 bits to the Sector Number. This
|
|
restricts users of this interface (i.e. boot managers hooked into
|
|
your disk's MBR as well as OS loaders hooked into the Boot Sectors)
|
|
to the following limits:
|
|
<itemizedlist>
|
|
<listitem><para>1024 cylinders, max</para></listitem>
|
|
<listitem><para>256 heads , max</para></listitem>
|
|
<listitem><para>64 sectors/track, max (actually 63, <literal>0</> isn't
|
|
available)</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>Now big hard disks have lots of cylinders but not a lot of
|
|
heads, so invariably with big hard disks the number of cylinders is
|
|
greater than 1024. Given this and the BIOS interface as is, you
|
|
can't boot off just anywhere on your hard disk. The boot code (the
|
|
boot manager and the OS loader hooked into all bootable partitions'
|
|
Boot Sectors) has to reside below cylinder 1024. In fact, if your
|
|
hard disk is typical and has 16 heads, this equates to:
|
|
<informalexample>
|
|
<para>1024 cyl/disk × 16 heads/disk × 63 sect/(cyl-head)
|
|
× 512 bytes/sector</para>
|
|
</informalexample>
|
|
</para>
|
|
|
|
<para>which is around the often-mentioned 528MB limit.</para>
|
|
|
|
<para>This is where BIOS LBA (Logical Block Addressing) comes in. BIOS LBA
|
|
gives the user of the BIOS API calls access to physical cylinders above
|
|
1024 though the BIOS interfaces by redefining a cylinder. That is, it
|
|
remaps your cylinders and heads, making it appear through the BIOS as
|
|
though the disk has fewer cylinders and more heads than it actually
|
|
does. In other words, it takes advantage of the fact that hard disks have
|
|
relatively few heads and lots of cylinders by shifting the balance between
|
|
number of cylinders and number of heads so that both numbers lie below the
|
|
above-mentioned limits (1024 cylinders, 256 heads).</para>
|
|
|
|
<para>With BIOS LBA, the hard disk size limitation is virtually
|
|
removed (well, pushed up to 8 Gigabytes anyway). If you have an LBA
|
|
BIOS, you can put FreeBSD or any OS anywhere you want and not hit the
|
|
1024 cylinder limit.</para>
|
|
|
|
<para>To use my 1.6 Gig Western Digital as an example again, it's
|
|
physical geometry is:
|
|
<informalexample>
|
|
<para>(3148 cyl, 16 heads, 63 sectors/track, 512 bytes/sector)</para>
|
|
</informalexample>
|
|
</para>
|
|
|
|
<para>However, my BIOS LBA remaps this to:
|
|
<informalexample>
|
|
<para>( 787 cyl, 64 heads, 63 sectors/track, 512 bytes/sector)</para>
|
|
</informalexample>
|
|
</para>
|
|
|
|
<para>giving the same effective size disk, but with cylinder and head
|
|
counts within the BIOS API's range (Incidentally, I have both Linux and
|
|
FreeBSD existing on one of my hard disks above the 1024th physical
|
|
cylinder, and both operating systems boot fine, thanks to BIOS LBA).</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Boot Managers and Disk Allocation</title>
|
|
|
|
<para>Another gotcha to watch out when installing boot managers is
|
|
allocating space for your boot manager. It's best to be aware of
|
|
this issue up front to save yourself from having to reinstall one or
|
|
more of your OSs.</para>
|
|
|
|
<para>If you followed the discussion in <xref linkend="booting">
|
|
about the Master Boot Sector (where the MBR is), Partition Boot
|
|
Sectors, and the booting process, you may have been wondering just
|
|
exactly where on your hard disk that nifty boot manager is going to
|
|
live. Well, some boot managers are small enough to fit entirely
|
|
within the Master Boot Sector (Cylinder 0, Head 0, Sector 0) along
|
|
with the partition table. Others need a bit more room and actually
|
|
extend a few sectors past the Master Boot Sector in the Cylinder 0
|
|
Head 0 track, since that's typically free…typically.</para>
|
|
|
|
<para>That's the catch. Some operating systems (FreeBSD included) let
|
|
you start their partitions right after the Master Boot Sector at
|
|
Cylinder 0, Head 0, Sector 2 if you want. In fact, if you give
|
|
FreeBSD's sysinstall a disk with an empty chunk up front or the whole
|
|
disk empty, that's where it'll start the FreeBSD partition by default
|
|
(at least it did when I fell into this trap). Then when you go to
|
|
install your boot manager, if it's one that occupies a few extra
|
|
sectors after the MBR, it'll overwrite the front of the first
|
|
partition's data. In the case of FreeBSD, this overwrites the
|
|
disk label, and renders your FreeBSD partition unbootable.</para>
|
|
|
|
<para>The easy way to avoid this problem (and leave yourself the
|
|
flexibility to try different boot managers later) is just to always
|
|
leave the first full track on your disk unallocated when you
|
|
partition your disk. That is, leave the space from Cylinder 0, Head
|
|
0, Sector 2 through Cylinder 0, Head 0, Sector 63 unallocated, and
|
|
start your first partition at Cylinder 0, Head 1, Sector 1.
|
|
For what it's worth, when you create a DOS partition at the
|
|
front of your disk, DOS leaves this space open by default (this is
|
|
why some boot managers assume it's free). So creating a DOS
|
|
partition up at the front of your disk avoids this problem
|
|
altogether. I like to do this myself, creating 1 Meg DOS partition
|
|
up front, because it also avoids my primary DOS drive letters
|
|
shifting later when I repartition.</para>
|
|
|
|
<para>For reference, the following boot managers use the
|
|
Master Boot Sector to store their code and data:
|
|
<itemizedlist>
|
|
|
|
<listitem>
|
|
<para>OS-BS 1.35</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Boot Easy</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>LILO</para>
|
|
</listitem>
|
|
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>These boot managers use a few additional sectors after the
|
|
Master Boot Sector:
|
|
<itemizedlist>
|
|
|
|
<listitem>
|
|
<para>OS-BS 2.0 Beta 8 (sectors 2-5)</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>OS/2's boot manager</para>
|
|
</listitem>
|
|
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>What if your machine won't boot?</title>
|
|
|
|
<para>At some point when installing boot managers, you might leave the
|
|
MBR in a state such that your machine won't boot. This is unlikely,
|
|
but possible when re-FDISKing underneath an already-installed boot
|
|
manager.</para>
|
|
|
|
<para>If you have a bootable DOS partition on your disk, you can boot
|
|
off a DOS floppy, and run:
|
|
<informalexample>
|
|
<screen>A:\> <userinput>FDISK /MBR</></screen>
|
|
</informalexample>
|
|
</para>
|
|
|
|
<para>to put the original, simple DOS boot code back into the system. You can
|
|
then boot DOS (and DOS only) off the hard drive. Alternatively, just
|
|
re-run your boot manager installation program off a bootable floppy.</para>
|
|
|
|
</sect2>
|
|
</sect1>
|
|
</chapter>
|
|
</book>
|