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First MB

Posted: Tue Jul 10, 2012 12:34 pm
by alexchamberlain
On the Arch image, the first MB is unused. What is the reason for this?

It is the same with the Debian image.

Re: First MB

Posted: Tue Jul 10, 2012 12:35 pm
by asb
You want to align your partitions to the SD card erase blocks (which are typically 1, 2, 4 megabytes). The wheezy images align partitions to 4MiB.

Re: First MB

Posted: Tue Jul 10, 2012 12:37 pm
by alexchamberlain
asb wrote:You want to align your partitions to the SD card erase blocks (which are typically 1, 2, 4 megabytes). The wheezy images align partitions to 4MiB.
I see, and you can't use the first MiB because of this? (0 is a multiple of 1, 2 and 4, right?)

What are erase blocks?

Re: First MB

Posted: Tue Jul 10, 2012 12:41 pm
by asb
Take a read of: http://lwn.net/Articles/428584/

You can't stick the first partition starting at 0 bytes because you need the partition table.

Re: First MB

Posted: Tue Jul 10, 2012 12:49 pm
by alexchamberlain
asb wrote:Take a read of: http://lwn.net/Articles/428584/

You can't stick the first partition starting at 0 bytes because you need the partition table.
I'd completely forgotten about the partition table! Thanks!