translate wiki( One )：Bios boot partition
Translation from wiki, The level is limited , If there is any mistake, please forgive me . original text ：https://en.wikipedia.org/wiki/BIOS_boot_partition
BIOS boot partition It's a partition ,gnu grub[ Translation notes 1]
<https://www.cnblogs.com/f-ck-need-u/p/7084627.html#blogf1> Use it to guide the legacy
bios But the boot device contains GPT The operating system of format partition table . This structure is sometimes referred to as BIOS/GPT start-up [ Translation notes 2]
The figure below is not the original content , Provided by me , For intuitive feeling bios boot partition .
boot Zoning is necessary , because GPT Use immediately following MBR After the sector to save the actual partition table , But in the traditional MBR In partition architecture , These sectors have no special function , As a result, there is not enough free space available for storage stage2 This paragraph boot
loader.MBR Also stored in boot loader, but MBR Cannot store more than 512 Contents of bytes , therefore MBR The passage in boot
loader Be treated as stage1 use , Its main function is to load more complex functions stage2 This paragraph boot loader,stage2 The operating system kernel can be read and loaded from the file system .
When used BIOS boot partition , The partition will contain stage2 Of boot loader program , for example grub2 file , and stage1 Of boot
loader The code remains in the MBR in . use bios boot Partitioning is not a solution based on tradition bios But it did gpt The only way to solve the problem of format disk , But it's complicated boot
loader as grub2 Cannot be fully compliant MBR Medium 398-446 Byte area , So they need a secondary storage space . stay MBR On disk , General use follows MBR After the sector space to store these complex boot
loader, These sector spaces are well known "MBR gap". And in the GPT On disk , Due to the lack of MBR gap Equivalent unused space , So use one alone bios
boot Partition to allocate such space , To store complex boot loader.
boot Partitioned GUID It can be "21686148-6449-6E6F-744E-656564454649". Based on BIOS Under the platform of GPT in ,BIOS
boot Partitioning is a bit like this EFI Under platform EFI system partition ,EFI System partition usage UEFI Save file systems and files , For BIOS Platform BIOS
boot Partitions do not use a file system to save code ( See the picture above , stay bios boot There is no file system created on the partition ).
bios boot The size of the partition is very small , It can be as small as 31kB( Because the first sector is mbr, therefore bios boot The contents of 2 Sector to No 63 a sector ), But because of the future boot
loader It may expand , So I suggest bios
boot Partition set to 1M size , And many disk partitioning tools use it 1MB Partition alignment policy , such MBR Some free space is reserved between the first partition .
stay Example 2 in ,grub 2 stay bios boot In the partition where it is stored core.img.
[ Translation notes 1]gnu grub： Now in use grub All of them gnu It's from the Shanzhai grub, original grub It has long been lost in history .
[ Translation notes 2]： that is bios MBR and gpt Mixed mode .