Thursday, August 15, 2013

Learning UEFI, GPT, and more

So... BIOS is being replaced with UEFI nearly everwhere. If you don't know how UEFI and it's underlying parts work, follow along!

In researching how UEFI works, I found it useful to first learn how GPT works. GPT is the GUID Partition Table which is designed as a replacement for MBR partitioning. All of this stems from the size and functional limitations of BIOS and MBR. Those were designed in an era when 16bits was a lot and when a few tens of MiB was outrageously expensive.

So, GPT partition uses larger offsets and different locations for where it writes information about the partitions on the disk. This enables support for massive disks which we'll see on newegg and amazon shelves in, say, oh, the next few years. :-D

In addition to this, GPT has some backwards compatibility with MBR partition tables that has odd side effects if you don't know about GPT. Basically, the old partition table is populated in a way such that MBR tools see one large unknown partition. This can easily lead an in-initiated to wipe out the MBR and install a new MBR partition table.

Start here for info on GPT: Wikipedia Article on GPT

Once you think you understand GPT, play a little with gdisk. (Keep in mind I am a Linux consumer, I will rarely show or demo anything that is particular to another OS.)

After you think you understand GPT, time to move on to UEFI. Start here: Wikipedia Article on UEFI

I'll share more as I learn more with regard to UEFI.

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