系统启动(1)-引导方式和分区表
原创
磁盘引导方式和分区表格式息息相关，不同的磁盘引导方式对应不同的分区表。
1. 引导方式
- BIOS,传统的（legacy）。
- UEFI
1.1. BIOS引导过程
上电，BIOS自检，确定引导介质，读取并加载引导介质中的引导程序，引导。磁盘的引导程序就在磁盘前512字节的最开始。
这个引导程序，只能支持MBR分区表格式。
有的文档会将这个引导程序称之为“主引导记录”，（就是MBR，Master Boot Record）。
1.2. UEFI引导过程
上电，UEFI，UEFI读取EFI引导程序，引导。
UEFI引导方式主要与GPT磁盘进行配合完成计算机的启动。GPT磁盘中包含了ESP隐藏分区，用于存放EFI引导程序。EFI引导程序会在计算机启动后，被UEFI固件加载继续执行引导流程。
2. 分区表格式
- MBR, 512字节，以55aa结尾。磁盘引导程序和磁盘分区信息保存在磁盘第一个扇区（扇区大小512B）的磁盘分区格式。
- GPT，0扇区（512字节）保留不用；1扇区~33扇区，分区表；倒数的扇区，和前面扇区对应，备份。
2.1. MBR样例
00000000 eb 63 90 10 8e d0 bc 00 b0 b8 00 00 8e d8 8e c0 |.c..............|
00000010 fb be 00 7c bf 00 06 b9 00 02 f3 a4 ea 21 06 00 |...|.........!..|
00000020 00 be be 07 38 04 75 0b 83 c6 10 81 fe fe 07 75 |....8.u........u|
00000030 f3 eb 16 b4 02 b0 01 bb 00 7c b2 80 8a 74 01 8b |.........|...t..|
00000040 4c 02 cd 13 ea 00 7c 00 00 eb fe 00 00 00 00 00 |L.....|.........|
00000050 00 00 00 00 00 00 00 00 00 00 00 80 01 00 00 00 |................|
00000060 00 00 00 00 ff fa 90 90 f6 c2 80 74 05 f6 c2 70 |...........t...p|
00000070 74 02 b2 80 ea 79 7c 00 00 31 c0 8e d8 8e d0 bc |t....y|..1......|
00000080 00 20 fb a0 64 7c 3c ff 74 02 88 c2 52 be 05 7c |. ..d|<.t...R..||
00000090 b4 41 bb aa 55 cd 13 5a 52 72 3d 81 fb 55 aa 75 |.A..U..ZRr=..U.u|
000000a0 37 83 e1 01 74 32 31 c0 89 44 04 40 88 44 ff 89 |7...t21..D.@.D..|
000000b0 44 02 c7 04 10 00 66 8b 1e 5c 7c 66 89 5c 08 66 |D.....f..\|f.\.f|
000000c0 8b 1e 60 7c 66 89 5c 0c c7 44 06 00 70 b4 42 cd |..`|f.\..D..p.B.|
000000d0 13 72 05 bb 00 70 eb 76 b4 08 cd 13 73 0d 5a 84 |.r...p.v....s.Z.|
000000e0 d2 0f 83 de 00 be 85 7d e9 82 00 66 0f b6 c6 88 |.......}...f....|
000000f0 64 ff 40 66 89 44 04 0f b6 d1 c1 e2 02 88 e8 88 |d.@f.D..........|
00000100 f4 40 89 44 08 0f b6 c2 c0 e8 02 66 89 04 66 a1 |.@.D.......f..f.|
00000110 60 7c 66 09 c0 75 4e 66 a1 5c 7c 66 31 d2 66 f7 |`|f..uNf.\|f1.f.|
00000120 34 88 d1 31 d2 66 f7 74 04 3b 44 08 7d 37 fe c1 |4..1.f.t.;D.}7..|
00000130 88 c5 30 c0 c1 e8 02 08 c1 88 d0 5a 88 c6 bb 00 |..0........Z....|
00000140 70 8e c3 31 db b8 01 02 cd 13 72 1e 8c c3 60 1e |p..1......r...`.|
00000150 b9 00 01 8e db 31 f6 bf 00 80 8e c6 fc f3 a5 1f |.....1..........|
00000160 61 ff 26 5a 7c be 80 7d eb 03 be 8f 7d e8 34 00 |a.&Z|..}....}.4.|
00000170 be 94 7d e8 2e 00 cd 18 eb fe 47 52 55 42 20 00 |..}.......GRUB .|
00000180 47 65 6f 6d 00 48 61 72 64 20 44 69 73 6b 00 52 |Geom.Hard Disk.R|
00000190 65 61 64 00 20 45 72 72 6f 72 0d 0a 00 bb 01 00 |ead. Error......|
000001a0 b4 0e cd 10 ac 3c 00 75 f4 c3 00 00 00 00 00 00 |.....<.u........|
000001b0 00 00 00 00 00 00 00 00 fd 45 09 00 00 00 80 20 |.........E..... |
000001c0 21 00 83 dd 1e 3f 00 08 00 00 00 a0 0f 00 00 dd |!....?..........|
000001d0 1f 3f 8e fe ff ff 00 a8 0f 00 00 58 bd 45 00 00 |.?.........X.E..|
000001e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.|2.2. GPT样例
扇区0，前512字节，保留
00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
000001b0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 80 00 |................|
000001c0 01 00 ee fe ff ff 01 00 00 00 ff ff ff ff 00 00 |................|
000001d0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.|
00000200扇区1，512字节，GPT头
[root@wwjk02-pa-dsj ~]# dd if=/dev/sdb bs=1 count=512 skip=$((512*1))|hexdump -C
00000000 45 46 49 20 50 41 52 54 00 00 01 00 5c 00 00 00 |EFI PART....\...|
00000010 81 5c d7 16 00 00 00 00 01 00 00 00 00 00 00 00 |.\..............|
00000020 ff ff 67 2e 02 00 00 00 22 00 00 00 00 00 00 00 |..g.....".......|
00000030 de ff 67 2e 02 00 00 00 da d0 c1 85 ae db 7b 47 |..g...........{G|
00000040 b2 c7 9a 05 16 98 41 6a 02 00 00 00 00 00 00 00 |......Aj........|
00000050 80 00 00 00 80 00 00 00 97 48 4c ad 00 00 00 00 |.........HL.....|
00000060 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000200扇区2~33，32个扇区，512*32，16KB，GPT分区表
[root@wwjk02-pa-dsj ~]# dd if=/dev/sdb bs=1 count=$((512*32)) skip=$((512*2))|hexdump -C
00000000 79 d3 d6 e6 07 f5 c2 44 a2 3c 23 8f 2a 3d f9 28 |y......D.<#.*=.(|
00000010 35 a4 f8 dc e8 f1 ee 4d 9c eb 7d 24 5a ba 2a e5 |5......M..}$Z.*.|
00000020 00 08 00 00 00 00 00 00 ff f7 67 2e 02 00 00 00 |..........g.....|
00000030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00004000原创声明：本文系作者授权腾讯云开发者社区发表，未经许可，不得转载。
如有侵权，请联系 cloudcommunity@tencent.com 删除。
原创声明：本文系作者授权腾讯云开发者社区发表，未经许可，不得转载。
如有侵权，请联系 cloudcommunity@tencent.com 删除。
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