In our earlier post describing Fastboot on our i.MX products, we passed the buck on how a Master Boot Record and partition table is constructed.
As shown in the Wikipedia article, there’s a lot of legacy involved in this important data structure and we’ll try to distill the important points here.
- Includes Cylinder/Head/Sector (CHS) numbering for legacy systems,
- Limited to four partitions and uses Extended Boot Records to define additional logical partitions within an Extended partition.
U-Boot supports supports five different partition types, although most builds support far fewer.
U-Boot also doesn’t appear to use CHS addressing for anything.
The CHS address space is used for placement of EBRs and serves as a unit of allocation by fdisk as described in this post.
More to come.