[arch-general] How big really is the MBR?

Eric Griffith egriffith92 at gmail.com
Sat Sep 3 18:09:10 EDT 2011

Whats up guys, Was planning on re-install Arch on my laptop, started
writing a couple scripts to handle the usual things I do. One of the
NEW things im going to be trying is grub2. Now, the Grub2 wiki says to

dd if=/dev/zero of=/dev/sda bs=440 count=1

to wipe out grub-legacy from the MBR.

And since the Arch-devs removed "No Bootloader" as an option in the
AIF, you can't follow the "during installation" instructions for

Here's my problem, just by sheer luck was I roaming the web today, and
noticed a few other threads (in various forums for various distros /
blogs) and they all had a similar command to run if youre grub-legacy
was screwed and you needed to write over it. The only issue, and the
reason for this email? They had different commands.

Not completly different, but different enough that raised an eyebrow. In

dd if=/dev/zero of=/dev/sda bs=440 count=1

They had various numbers for bs=,  some 440, some 446, some 506, and
some 512. Normally I would've just shrugged and followed the wiki, but
notice on one said that if you zero out too far, you wipe out hte
partition table...which I wouldn't enjoy haha.

So can anyone confirm that the command above, from the wiki, is
correct? And that it IS 440, and not something different. I'd hate to
pick the wrong one and zero out my partition table, or not completly
zero out grub-legacy and run into a whole different set of problems.


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