163 lines
9.2 KiB
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163 lines
9.2 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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<HTML>
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<HEAD>
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<title>Boot Disk Failure and Recovery LG #39</title>
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<BODY BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#A000A0"
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ALINK="#FF0000">
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<H4>
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"Linux Gazette...<I>making Linux just a little more fun!</I>"
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</H4>
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<P> <HR> <P>
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<center>
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<H1><font color="maroon">Boot Disk Failure and Recovery</font></H1>
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<H4>By <a href="mailto:chguy@chguy.net">Bill Bennet</a></H4>
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</center>
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<P> <HR> <P>
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So you think it can't happen to you? Well, this is the scene:
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<ol>
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<li> First, get bored while waiting around for something.
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<li> Even worse, read a Y2K warning that says you can change your system
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time manually to avoid trouble.
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<li> Next, decide to go into the system setup and look at your CMOS settings
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to see what you can see.
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<li> Then make a terrible decision; like "Hey, the system time is off by a
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few minutes. I will correct the time."
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<li> Then do a dumb thing, like change the system time in the CMOS settings.
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<li> Reboot and get this message:"BOOT DISK FAILURE. Please insert a system
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disk and reboot."
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</ol>
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<P>
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What did I do? I
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recovered the system with linux, thats what I did. The system here is set up
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to dual boot with Windows95 and three different Linux distributions via
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<a href="#lilo">LILO</a>,
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the Linux boot loader.
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<P> Since the Master Boot
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Record on sector 0 is booting DOS and Linux, I thought it was <a href="#scared">
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prudent </a>to use
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the DOS version of fdisk to try to recover the partition table. Ha! "What a
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lack of features you have, Grandma."said little Red LinuxHat.
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<h2><font color=blue>Sys a:</font></h2>
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<P> The job I tried to do
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was to boot with my Windows95 rescue disk, which you make before this ever
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happens. You do have one, don't you? For a simple boot diskette, pop a floppy
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in the "A:" drive and type "sys a:".
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<P> Once the diskette
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boots, you try to cd to "C:" drive. Ha! It is not there. It is gone. The first
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thing to try is fdisk (DOS), to see what it can do. The upshot is that it don't
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do much. All that fdisk (DOS) said to me was that the hard disk was empty,
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with no partitions. Yikes, what a mess. The other hard disk, which has two DOS
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partitions, was fine. BUT, the Master Boot Record was gone. I used the command
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fdisk /MBR and nothing happened, nothing changed. According to
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<a href="#fdisk">fdisk</a> (DOS), there was no partition table, no partition
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and you are out of luck. I suppose this lack of features is designed to have
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me running to a data recovery specialist to get "saved" for a fair exchange
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of dollars.
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<h2><font color=blue>Enter Linux</font></h2>
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<P> Now that you have
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proved that the other system is lacking some power, it is time to boot linux.
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I grabbed a boot disk, which you make before this ever happens. You do have
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one, don't you? In RedHat you simply put a blank diskette in the floppy drive
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and type mkbootdisk. Man oh man, I love linux! No clickety-clicks, no waiting,
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just service and super powers. I guess it helps when your software is written
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by the best and brightest minds in a free thought environment.
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<P> The RedHat boot image
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for installation is also a rescue diskette. Tell it you are doing the "expert"
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mode (I am not but you may be one) and press "Enter". Tell it if you have a
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colour terminal and configure the keyboard. Now put in the supp.img diskette
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and press "Enter". You get a "# _" prompt. Type this:<pre>
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mknod /dev/hda b 3 0</pre>
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<P> Now you have a new
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device called /dev/hda. It is your original old hard disk drive.
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<P>
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The next thing is to mount your old root partition and run lilo. So cd to /
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and make a new directory to mount the thing: mkdir any_name_will_do.
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Type this:<pre>
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mount /dev/hd_your_root_partition_here /any_name_will_do</pre>
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<P>
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Then cd to /any_name_will_do/sbin and run lilo. Type this:<pre>
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./lilo -C /any_name_will_do/etc/lilo.conf</pre>
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<h2><font color=blue>Super Powers</font></h2>
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<P> The fdisk
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(GNU/Linux) is able to make your partitions and set the file type for them.
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Also, it can verify the partition table. So, in my time of need this is what
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I did. I typed "v" for verify.
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<P> The program reported
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to me that the partition table had been altered! No kidding. Then I typed "w"
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to write the table to the disk and quit fdisk.
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<h2><font color=blue>Reboot and hope</font></h2>
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<P> The system rebooted
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perfectly as usual. Linux wins again.
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<P>
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<h2><font color=blue><a name=lilo>Leeloo</a>'s name was a peek at the future</font></h2>
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<P> Yeah, I watched the
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Fifth Element several times. The LILO boot loader can easily re-write the
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Master Boot Record just by running it once on its /etc/lilo.conf file. Type
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/sbin/lilo and the job is done. You may now boot from the hard disk drive.
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<h2><font color=blue>There can be only <a name="fdisk">One</a></font></h2>
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<P>
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The DOS fdisk can alter your view of the world. When
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you have only one hard disk drive it will let you make one and only one
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primary partition. If you have a second HDD it will let you make the four
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primary partitions allowed by the PC's designers or three primary and one
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extended.
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<P>
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When you have only one primary partition then you can't be trying to boot
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more than one type of Operating System. Normally, that is. Linux can boot from
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a logical drive on an extended partition with loadlin.exe.
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<P>
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I guess it must be too hard to compete on the merits of the product, so the
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DOS Borg must use this type of anti-competitive approach in order to maintain
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market share. Just imagine one primary partition covering 100% of the disk.
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"Yeah, that will keep them from even <i>trying </i>to get a real OS".
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<P> Frighten them with dire
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warnings, too. Tell them their system has performed illegal operations and
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general protection faults.
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<P> In my mind, Microsoft
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is the illegal operation and the DOJ is guilty of general protection faults
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from not protecting the public in general.
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<P>
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<hr>
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<h2><a name=scared><font color=blue>Scared of the Beast</font></a></h2>
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<p>With good reason, too. DOS always writes over the Master Boot Record when you
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install it. The beast has the arrogance to exclude all other possible operating
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systems when it is time to install. This is not an oversight, it is not a test.
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You are caught square in the middle of the cut-throat world of big business.
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Get used to it gentle linuxian, your system has been discovered by the rest of
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the world. They say "Defend your turf or die". I say "remember the Apple" and
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let us not have it happen again that an excellent system gets shoved aside and
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marginalized as a specialty item. Linux can do EVERYTHING. Lets bring it on!
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<hr><h2><a name=xfree><font color=blue>Reference reading:</font></a></h2>
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<P>Clock mini-HOWTO -- required reading for real-time Linuxians
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<P>Large Disk mini-HOWTO -- excellent Master Boot Record discussion
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<P>Linux+DOS+Win95 mini-HOWTO -- here's a good /etc/lilo.conf example
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<P>Partition mini-HOWTO -- required reading for all linuxians
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<hr><br><P>
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<center><font color=blue><strong>made with mcedit on an i486 with GNU/Linux 2.0.35</strong></font><P><font color=blue><strong>The adamant position of the author is in no way meant as an affront to sincere readers.</strong></font></center>
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<!--===================================================================-->
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<P> <hr> <P>
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<center><H5>Copyright © 1999, Bill Bennet <BR>
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Published in Issue 39 of <i>Linux Gazette</i>, March 1999</H5></center>
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