Speakup and vinux

Wed Jan 6 15:31:06 EST 2010

the mbr contains code that boots the first active partition so zeroing out 
the mbr will render your drive unbootable.

All operating systems since ms-dos 2.0 placed code to boot the first active 
partition into the mbr, since windows 95 this mbr now uses and understands 
lba addressing and in the case of linux's code can boot something beyond 
8.4gb.
Regards, Kerry.

----- Original Message ----- 
From: "Georgina Joyce" <r2gl at o2.co.uk>
To: "Speakup is a screen review system for Linux." <speakup at braille.uwo.ca>
Sent: Thursday, January 07, 2010 12:30 AM
Subject: Re: Speakup and vinux

Hi Kerry,

Is there anything in the MBR?  My memory reminds me that in the days of
Win 9x, to remove grub or lilo signatures we just wrote zeros to the MBR
which then resumed the booting to command.com etc.  So does 2000, XP
Vista put something in the MBR?

Thanks.

On Wed, 2010-01-06 at 10:52 +1100, Kerry Hoath wrote:
> Technically this is incorrect, the command you gave backs up both the mbr
> and partition table.
> If you then install Linux and restore this sector it will remove the
> partition entries where Linux was installed, rendering windows bootable 
> and
> Linux invisible.
>
> You would be better to back up the mbr with the following command:
> dd bs=446 count=1 if=/dev/sda of=winmbr.bin
> replacing /dev/sda with the correct block device for your hard disk.
> The first 446 bytes contain the mbr and the last bytes minus 2 contain the
> partition table.
> The last 2  bytes of the sector are set to 0X55AA or 0XAA55 to show the 
> bios
> the drive contains bootable operating system(s).
>
> Generally it is good practice to set 1 partition active however if Grub 
> Lilo
> or another boot manager controlls the mbr this is not required.
> Some bioses will refuse to consider a drive bootable unless 1 of the
> partitions is set active.
> Regards, Kerry.
>
>
> ----- Original Message ----- 
> From: "Øyvind Lode" <oyvind.lode at lyse.net>
> To: "'Speakup is a screen review system for Linux.'"
> <speakup at braille.uwo.ca>
> Sent: Wednesday, January 06, 2010 8:30 AM
> Subject: RE: Speakup and vinux
>
>
> > If you decide to install, backup the MBR (which now stores the windows
> > boot
> > loader) before installing.
> > If you do a mistake with grub you can just restore the MBR and Windows
> > will
> > boot as normal again.
> >
> > Use dd to backup:
> >
> > # dd if=/dev/sda of=windows-mbr.img bs=512 count=1
> >
> > If you need to restore:
> > # dd if=windows-mbr.img of=/dev/sda bs=512 count=1
> >
> > When restoring the MBR be sure that you type the command correctly and
> > make
> > sure you don't accidently use a different file.
> > If you accidently dd with a file not containing a MBR, dd will just 
> > write
> > 512 blocks from that file to the MBR on the harddrive...
> > That will efficiently destroy the MBR.
> >
> > Also be sure to use the proper device for your HD.
> > /dev/sda may not be the correct one on your system.
> > Most likely /dev/hda if it's an old IDE disk.
> >
> >
> >
> > -----Original Message-----
> > From: speakup-bounces at braille.uwo.ca
> > [mailto:speakup-bounces at braille.uwo.ca]
> > On Behalf Of Martin McCormick
> > Sent: 5. januar 2010 22:01
> > To: Speakup is a screen review system for Linux.
> > Subject: Re: Speakup and vinux
> >
> > It should load just fine as the operating system with speakup
> > appears to take up a couple of gigabytes. The middle-sized ISO image is
> > around 400 megabytes and gives you enough to get started. I remember the
> > painful feeling when I first started using Unix in 1989. It is easy to
> > forget things that now seem second nature but were once show stoppers.
> >
> > If you are familiar with Linux, vinux is standard Debian Linux with
> > speech on the console. If you are new to Unix, find a friend who knows
> > more
> > than you do to at least help you get started. Remember that if you are 
> > not
> > root, you can't hurt much except for deleting your own files. There is 
> > no
> > undelete that works well as Unix systems are always doing something with
> > files and sectors that you don't need any more are marked as free and 
> > the
> > OS
> > may just snap them right up a second later and turn them in to syslog or
> > something else.
> >
> > Unix and all its various flavors like Sunos, AIX and FreeBSD to name
> > a few, don't require defragmentation of the hard drive as they 
> > constantly
> > act like a very thorough file clerk in an office who can't stand to see
> > disorder so they are always looking for pieces of files and making sure
> > they
> > all fit together in contiguous blocks so that the OS doesn't have to 
> > waste
> > time to gather them from here and there. In other words, when you rm a
> > file,
> > it is often-times gone for good for all practical purposes.
> >
> > The nice thing about a live CD is that you do not have to write so
> > much as one byte to your hard drive in order to test it out. Burn the 
> > iso
> > image to a CDROM and boot from that. As long as you don't run the
> > installer,
> > you aren't going to modify your present setup. You will hear it start to
> > talk some time after the boot process starts and you will get a shell 
> > just
> > as if you were logged in.
> >
> > Be really careful if you decide to install it as you don't want to
> > destroy your Windows partitions. You can set it up so that you have a
> > short
> > time to decide whether you want to boot Windows or Linux. One thing to
> > watch
> > out for is that the boot sector for Linux mustn't clobber the Windows 
> > boot
> > sector. It does sometimes happen. I haven't ever set up a multiple-boot
> > system so I can't help much there
> >
> > The best of luck as you learn about vinux.
> >
> > Martin McCormick
> > _______________________________________________
> > Speakup mailing list
> > Speakup at braille.uwo.ca
> > http://speech.braille.uwo.ca/mailman/listinfo/speakup
> >
> > _______________________________________________
> > Speakup mailing list
> > Speakup at braille.uwo.ca
> > http://speech.braille.uwo.ca/mailman/listinfo/speakup
> >
>
> _______________________________________________
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-- 
Gena

four kinds of freedom, for the users of the software:

    * The freedom to run the program, for any purpose (freedom 0).
    * The freedom to study how the program works, and adapt it to your
needs (freedom 1). Access to the source code is a precondition for this.
    * The freedom to redistribute copies so you can help your neighbor
(freedom 2).
    * The freedom to improve the program, and release your improvements
to the public, so that the whole community benefits (freedom 3). Access
to the source code is a precondition for this.

Richard Matthew Stallman

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