接磁盘逻辑结构浅谈-MBR和分区，我们接着说说有关的扩展结构-逻辑分区。因为LVM也偶尔制造一些麻烦，所以我们也捎带说说LVM。
EBR：扩展分区和逻辑分区
扩展分区和逻辑分区之关系
由于MBR里磁盘分区结构只有64字节的空间可用，而每个分区项需要16个字节，因此，MBR里最多只能存储4个分区。这就是为什么会有扩展分区和逻辑分区的原因：在一块磁盘上不受限于只能有4个分区，可以按需制作多个分区。那么，扩展分区是怎么实现的呢？
扩展分区和逻辑分区的关系，可以用下图表示，其中绿色块代表的是2048块扇区。很明显，每个逻辑分区前面都有2048块没有使用的扇区
逻辑分区的分区数据，就存储在这些没有使用的扇区里，准确的说，是储存在其中的第一个扇区里（这个扇区叫做扩展引导扇区，简称EBR）。虽然EBR使用和MBR一样的分区表结构。但是，不同于MBR分区表，每个EBR分区表都只是使用前两项记录。一项记录当前的逻辑分区，一项记录下一个逻辑分区。这样，EBR数据之间就构成了一个树结构，可以任意扩展
当然，这也意味着每个逻辑分区，除了第一个逻辑分区外，都是有两条分区数据的。有趣的是，这两条记录并不完全一样。
让我们综合一下。从MBR分区数据我们能够确定扩展分区，然后根据扩展分区，我们可以确定逻辑分区
验证
我们使用如下的数据来验证扩展分区和逻辑分区以及其间之关系
我们首先验证每个逻辑分区前都有2048块空闲扇区
接下来我们验证这些空闲的2048块扇区的第一块扇区里都有两个分区数据。当然，最后一块逻辑分区例外
一个逻辑分区的两条记录并不一致
我们验证一下fdisk的输出和磁盘MBR和EBR记录之间的关系
用到的命令
dd if=/dev/sdb bs=1 count=64 skip=446 2>/dev/null | od -v -tx1
for n in 14336 4210688 8407040;do \
fisrt_sector_number=$(expr $n - 2048);\
dd if=/dev/sdb bs=1 count=64 skip=$(expr ${fisrt_sector_number} \* 512 + 446) 2>/dev/null | \
od -v -tx1;\
done
{
dd if=/dev/sdb bs=1 count=64 skip=446 2>/dev/null | od -v -tx1;\
for n in 14336 4210688 8407040;do \
fisrt_sector_number=$(expr $n - 2048);\
dd if=/dev/sdb bs=1 count=64 skip=$(expr ${fisrt_sector_number} \* 512 + 446) 2>/dev/null | \
od -v -tx1;\
done
} | \
perl -nE '
chomp;print qq[$_ ];
if (/\s[0-9a-f]+\s*/) {
@fields = split;
print hex(qq{$fields[11]$fields[10]$fields[9]$fileds[8]});
}
print qq[\n];'LVM：又一层包装
我们直接给出LVM的实际例子，供大家自行分析如下信息
- 物理卷
- 卷组
- 逻辑卷
很明显，LVM有关的数据结构和关系都是记录在磁盘上的。
## LVM分区信息
[root@localhost ~]# cat lvm.info
--- Physical volume ---
PV Name /dev/vda5
VG Name ubuntu
PV Size 9.76 GiB / not usable 2.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 2498
Free PE 0
Allocated PE 2498
PV UUID AIie9r-pdTS-09Za-cATW-UC6j-n3lO-4rraGc
--- Volume group ---
VG Name ubuntu
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 3
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 2
Max PV 0
Cur PV 1
Act PV 1
VG Size 9.76 GiB
PE Size 4.00 MiB
Total PE 2498
Alloc PE / Size 2498 / 9.76 GiB
Free PE / Size 0 / 0
VG UUID padOl1-EPWN-At1M-3GJk-MgFR-mPic-GATrFp
--- Logical volume ---
LV Name /dev/ubuntu/root
VG Name ubuntu
LV UUID qjonzd-yqJh-cLi1-KZvh-0x6H-W9zB-Fy26Ic
LV Write Access read/write
LV Status available
# open 1
LV Size 9.29 GiB
Current LE 2379
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 251:0
--- Logical volume ---
LV Name /dev/ubuntu/swap_1
VG Name ubuntu
LV UUID HiLDjt-0TVl-zNj2-QxIM-Vl7m-Upsd-Nyfcjw
LV Write Access read/write
LV Status available
# open 1
LV Size 476.00 MiB
Current LE 119
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 251:1
[root@iZ2ze3shz9b6z00qqhjoyzZ ~]### 二进制编辑器里的LVM信息
00000000: 4c41 4245 4c4f 4e45 0100 0000 0000 0000 LABELONE........
00000010: 9ebe 7a39 2000 0000 4c56 4d32 2030 3031 ..z9 ...LVM2 001
00000020: 4149 6965 3972 7064 5453 3039 5a61 6341 AIie9rpdTS09ZacA
00000030: 5457 5543 366a 6e33 6c4f 3472 7261 4763 TWUC6jn3lO4rraGc
00000040: 0000 a070 0200 0000 0000 0300 0000 0000 ...p............
...
00000e00: 1a37 8d62 204c 564d 3220 785b 3541 2572 .7.b LVM2 x[5A%r
00000e10: 304e 2a3e 0100 0000 0010 0000 0000 0000 0N*>............
00000e20: 00f0 0200 0000 0000 000a 0000 0000 0000 ................
00000e30: 8e04 0000 0000 0000 c279 ed59 0000 0000 .........y.Y....
00000e40: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000e50: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000e60: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000e70: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000e80: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000e90: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000ea0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000eb0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000ec0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000ed0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000ee0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000ef0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000f00: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000f10: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000f20: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000f30: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000f40: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000f50: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000f60: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000f70: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000f80: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000f90: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000fa0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000fb0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000fc0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000fd0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000fe0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000ff0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001000: 7562 756e 7475 207b 0a69 6420 3d20 2270 ubuntu {.id = "p
00001010: 6164 4f6c 312d 4550 574e 2d41 7431 4d2d adOl1-EPWN-At1M-
00001020: 3347 4a6b 2d4d 6746 522d 6d50 6963 2d47 3GJk-MgFR-mPic-G
00001030: 4154 7246 7022 0a73 6571 6e6f 203d 2031 ATrFp".seqno = 1
00001040: 0a73 7461 7475 7320 3d20 5b22 5245 5349 .status = ["RESI
00001050: 5a45 4142 4c45 222c 2022 5245 4144 222c ZEABLE", "READ",
00001060: 2022 5752 4954 4522 5d0a 666c 6167 7320 "WRITE"].flags
00001070: 3d20 5b5d 0a65 7874 656e 745f 7369 7a65 = [].extent_size
00001080: 203d 2038 3139 320a 6d61 785f 6c76 203d = 8192.max_lv =
00001090: 2030 0a6d 6178 5f70 7620 3d20 300a 0a70 0.max_pv = 0..p
000010a0: 6879 7369 6361 6c5f 766f 6c75 6d65 7320 hysical_volumes
000010b0: 7b0a 0a70 7630 207b 0a69 6420 3d20 2241 {..pv0 {.id = "A
000010c0: 4969 6539 722d 7064 5453 2d30 395a 612d Iie9r-pdTS-09Za-
000010d0: 6341 5457 2d55 4336 6a2d 6e33 6c4f 2d34 cATW-UC6j-n3lO-4
000010e0: 7272 6147 6322 0a64 6576 6963 6520 3d20 rraGc".device =
000010f0: 222f 6465 762f 7364 6135 220a 0a73 7461 "/dev/sda5"..sta
00001100: 7475 7320 3d20 5b22 414c 4c4f 4341 5441 tus = ["ALLOCATA
00001110: 424c 4522 5d0a 666c 6167 7320 3d20 5b5d BLE"].flags = []
00001120: 0a64 6576 5f73 697a 6520 3d20 3230 3436 .dev_size = 2046
00001130: 3737 3132 0a70 655f 7374 6172 7420 3d20 7712.pe_start =
00001140: 3338 340a 7065 5f63 6f75 6e74 203d 2032 384.pe_count = 2
00001150: 3439 380a 7d0a 7d0a 0a7d 0a23 2047 656e 498.}.}..}.# Gen
00001160: 6572 6174 6564 2062 7920 4c56 4d32 2076 erated by LVM2 v
00001170: 6572 7369 6f6e 2032 2e30 322e 3534 2831 ersion 2.02.54(1
00001180: 2920 2832 3030 392d 3130 2d32 3629 3a20 ) (2009-10-26):
00001190: 4d6f 6e20 4170 7220 3234 2030 383a 3534 Mon Apr 24 08:54
000011a0: 3a31 3920 3230 3137 0a0a 636f 6e74 656e :19 2017..conten
000011b0: 7473 203d 2022 5465 7874 2046 6f72 6d61 ts = "Text Forma
000011c0: 7420 566f 6c75 6d65 2047 726f 7570 220a t Volume Group".
000011d0: 7665 7273 696f 6e20 3d20 310a 0a64 6573 version = 1..des
000011e0: 6372 6970 7469 6f6e 203d 2022 220a 0a63 cription = ""..c
000011f0: 7265 6174 696f 6e5f 686f 7374 203d 2022 reation_host = "
00001200: 7562 756e 7475 2209 2320 4c69 6e75 7820 ubuntu".# Linux
00001210: 7562 756e 7475 2032 2e36 2e33 322d 3231 ubuntu 2.6.32-21
00001220: 2d67 656e 6572 6963 2023 3332 2d55 6275 -generic #32-Ubu
00001230: 6e74 7520 534d 5020 4672 6920 4170 7220 ntu SMP Fri Apr
00001240: 3136 2030 383a 3130 3a30 3220 5554 4320 16 08:10:02 UTC
00001250: 3230 3130 2069 3638 360a 6372 6561 7469 2010 i686.creati
00001260: 6f6e 5f74 696d 6520 3d20 3134 3933 3032 on_time = 149302
00001270: 3430 3539 0923 204d 6f6e 2041 7072 2032 4059.# Mon Apr 2
00001280: 3420 3038 3a35 343a 3139 2032 3031 370a 4 08:54:19 2017.
00001290: 0a00 0000 0000 0000 0000 0000 0000 0000 ................
...
00001400: 7562 756e 7475 207b 0a69 6420 3d20 2270 ubuntu {.id = "p
00001410: 6164 4f6c 312d 4550 574e 2d41 7431 4d2d adOl1-EPWN-At1M-
00001420: 3347 4a6b 2d4d 6746 522d 6d50 6963 2d47 3GJk-MgFR-mPic-G
00001430: 4154 7246 7022 0a73 6571 6e6f 203d 2032 ATrFp".seqno = 2
00001440: 0a73 7461 7475 7320 3d20 5b22 5245 5349 .status = ["RESI
00001450: 5a45 4142 4c45 222c 2022 5245 4144 222c ZEABLE", "READ",
00001460: 2022 5752 4954 4522 5d0a 666c 6167 7320 "WRITE"].flags
00001470: 3d20 5b5d 0a65 7874 656e 745f 7369 7a65 = [].extent_size
00001480: 203d 2038 3139 320a 6d61 785f 6c76 203d = 8192.max_lv =
00001490: 2030 0a6d 6178 5f70 7620 3d20 300a 0a70 0.max_pv = 0..p
000014a0: 6879 7369 6361 6c5f 766f 6c75 6d65 7320 hysical_volumes
000014b0: 7b0a 0a70 7630 207b 0a69 6420 3d20 2241 {..pv0 {.id = "A
000014c0: 4969 6539 722d 7064 5453 2d30 395a 612d Iie9r-pdTS-09Za-
000014d0: 6341 5457 2d55 4336 6a2d 6e33 6c4f 2d34 cATW-UC6j-n3lO-4
000014e0: 7272 6147 6322 0a64 6576 6963 6520 3d20 rraGc".device =
000014f0: 222f 6465 762f 7364 6135 220a 0a73 7461 "/dev/sda5"..sta
00001500: 7475 7320 3d20 5b22 414c 4c4f 4341 5441 tus = ["ALLOCATA
00001510: 424c 4522 5d0a 666c 6167 7320 3d20 5b5d BLE"].flags = []
00001520: 0a64 6576 5f73 697a 6520 3d20 3230 3436 .dev_size = 2046
00001530: 3737 3132 0a70 655f 7374 6172 7420 3d20 7712.pe_start =
00001540: 3338 340a 7065 5f63 6f75 6e74 203d 2032 384.pe_count = 2
00001550: 3439 380a 7d0a 7d0a 0a6c 6f67 6963 616c 498.}.}..logical
00001560: 5f76 6f6c 756d 6573 207b 0a0a 726f 6f74 _volumes {..root
00001570: 207b 0a69 6420 3d20 2271 6a6f 6e7a 642d {.id = "qjonzd-
00001580: 7971 4a68 2d63 4c69 312d 4b5a 7668 2d30 yqJh-cLi1-KZvh-0
00001590: 7836 482d 5739 7a42 2d46 7932 3649 6322 x6H-W9zB-Fy26Ic"
000015a0: 0a73 7461 7475 7320 3d20 5b22 5245 4144 .status = ["READ
000015b0: 222c 2022 5752 4954 4522 2c20 2256 4953 ", "WRITE", "VIS
000015c0: 4942 4c45 225d 0a66 6c61 6773 203d 205b IBLE"].flags = [
000015d0: 5d0a 7365 676d 656e 745f 636f 756e 7420 ].segment_count
000015e0: 3d20 310a 0a73 6567 6d65 6e74 3120 7b0a = 1..segment1 {.
000015f0: 7374 6172 745f 6578 7465 6e74 203d 2030 start_extent = 0
00001600: 0a65 7874 656e 745f 636f 756e 7420 3d20 .extent_count =
00001610: 3233 3739 0a0a 7479 7065 203d 2022 7374 2379..type = "st
00001620: 7269 7065 6422 0a73 7472 6970 655f 636f riped".stripe_co
00001630: 756e 7420 3d20 3109 2320 6c69 6e65 6172 unt = 1.# linear
00001640: 0a0a 7374 7269 7065 7320 3d20 5b0a 2270 ..stripes = [."p
00001650: 7630 222c 2030 0a5d 0a7d 0a7d 0a7d 0a7d v0", 0.].}.}.}.}
00001660: 0a23 2047 656e 6572 6174 6564 2062 7920 .# Generated by
00001670: 4c56 4d32 2076 6572 7369 6f6e 2032 2e30 LVM2 version 2.0
00001680: 322e 3534 2831 2920 2832 3030 392d 3130 2.54(1) (2009-10
00001690: 2d32 3629 3a20 4d6f 6e20 4170 7220 3234 -26): Mon Apr 24
000016a0: 2030 383a 3534 3a32 3120 3230 3137 0a0a 08:54:21 2017..
000016b0: 636f 6e74 656e 7473 203d 2022 5465 7874 contents = "Text
000016c0: 2046 6f72 6d61 7420 566f 6c75 6d65 2047 Format Volume G
000016d0: 726f 7570 220a 7665 7273 696f 6e20 3d20 roup".version =
000016e0: 310a 0a64 6573 6372 6970 7469 6f6e 203d 1..description =
000016f0: 2022 220a 0a63 7265 6174 696f 6e5f 686f ""..creation_ho
00001700: 7374 203d 2022 7562 756e 7475 2209 2320 st = "ubuntu".#
00001710: 4c69 6e75 7820 7562 756e 7475 2032 2e36 Linux ubuntu 2.6
00001720: 2e33 322d 3231 2d67 656e 6572 6963 2023 .32-21-generic #
00001730: 3332 2d55 6275 6e74 7520 534d 5020 4672 32-Ubuntu SMP Fr
00001740: 6920 4170 7220 3136 2030 383a 3130 3a30 i Apr 16 08:10:0
00001750: 3220 5554 4320 3230 3130 2069 3638 360a 2 UTC 2010 i686.
00001760: 6372 6561 7469 6f6e 5f74 696d 6520 3d20 creation_time =
00001770: 3134 3933 3032 3430 3631 0923 204d 6f6e 1493024061.# Mon
00001780: 2041 7072 2032 3420 3038 3a35 343a 3231 Apr 24 08:54:21
00001790: 2032 3031 370a 0a00 0000 0000 0000 0000 2017...........
000017a0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
000017b0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
000017c0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
000017d0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
000017e0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
000017f0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001800: 7562 756e 7475 207b 0a69 6420 3d20 2270 ubuntu {.id = "p
00001810: 6164 4f6c 312d 4550 574e 2d41 7431 4d2d adOl1-EPWN-At1M-
00001820: 3347 4a6b 2d4d 6746 522d 6d50 6963 2d47 3GJk-MgFR-mPic-G
00001830: 4154 7246 7022 0a73 6571 6e6f 203d 2033 ATrFp".seqno = 3
00001840: 0a73 7461 7475 7320 3d20 5b22 5245 5349 .status = ["RESI
00001850: 5a45 4142 4c45 222c 2022 5245 4144 222c ZEABLE", "READ",
00001860: 2022 5752 4954 4522 5d0a 666c 6167 7320 "WRITE"].flags
00001870: 3d20 5b5d 0a65 7874 656e 745f 7369 7a65 = [].extent_size
00001880: 203d 2038 3139 320a 6d61 785f 6c76 203d = 8192.max_lv =
00001890: 2030 0a6d 6178 5f70 7620 3d20 300a 0a70 0.max_pv = 0..p
000018a0: 6879 7369 6361 6c5f 766f 6c75 6d65 7320 hysical_volumes
000018b0: 7b0a 0a70 7630 207b 0a69 6420 3d20 2241 {..pv0 {.id = "A
000018c0: 4969 6539 722d 7064 5453 2d30 395a 612d Iie9r-pdTS-09Za-
000018d0: 6341 5457 2d55 4336 6a2d 6e33 6c4f 2d34 cATW-UC6j-n3lO-4
000018e0: 7272 6147 6322 0a64 6576 6963 6520 3d20 rraGc".device =
000018f0: 222f 6465 762f 7364 6135 220a 0a73 7461 "/dev/sda5"..sta
00001900: 7475 7320 3d20 5b22 414c 4c4f 4341 5441 tus = ["ALLOCATA
00001910: 424c 4522 5d0a 666c 6167 7320 3d20 5b5d BLE"].flags = []
00001920: 0a64 6576 5f73 697a 6520 3d20 3230 3436 .dev_size = 2046
00001930: 3737 3132 0a70 655f 7374 6172 7420 3d20 7712.pe_start =
00001940: 3338 340a 7065 5f63 6f75 6e74 203d 2032 384.pe_count = 2
00001950: 3439 380a 7d0a 7d0a 0a6c 6f67 6963 616c 498.}.}..logical
00001960: 5f76 6f6c 756d 6573 207b 0a0a 726f 6f74 _volumes {..root
00001970: 207b 0a69 6420 3d20 2271 6a6f 6e7a 642d {.id = "qjonzd-
00001980: 7971 4a68 2d63 4c69 312d 4b5a 7668 2d30 yqJh-cLi1-KZvh-0
00001990: 7836 482d 5739 7a42 2d46 7932 3649 6322 x6H-W9zB-Fy26Ic"
000019a0: 0a73 7461 7475 7320 3d20 5b22 5245 4144 .status = ["READ
000019b0: 222c 2022 5752 4954 4522 2c20 2256 4953 ", "WRITE", "VIS
000019c0: 4942 4c45 225d 0a66 6c61 6773 203d 205b IBLE"].flags = [
000019d0: 5d0a 7365 676d 656e 745f 636f 756e 7420 ].segment_count
000019e0: 3d20 310a 0a73 6567 6d65 6e74 3120 7b0a = 1..segment1 {.
000019f0: 7374 6172 745f 6578 7465 6e74 203d 2030 start_extent = 0
00001a00: 0a65 7874 656e 745f 636f 756e 7420 3d20 .extent_count =
00001a10: 3233 3739 0a0a 7479 7065 203d 2022 7374 2379..type = "st
00001a20: 7269 7065 6422 0a73 7472 6970 655f 636f riped".stripe_co
00001a30: 756e 7420 3d20 3109 2320 6c69 6e65 6172 unt = 1.# linear
00001a40: 0a0a 7374 7269 7065 7320 3d20 5b0a 2270 ..stripes = [."p
00001a50: 7630 222c 2030 0a5d 0a7d 0a7d 0a0a 7377 v0", 0.].}.}..sw
00001a60: 6170 5f31 207b 0a69 6420 3d20 2248 694c ap_1 {.id = "HiL
00001a70: 446a 742d 3054 566c 2d7a 4e6a 322d 5178 Djt-0TVl-zNj2-Qx
00001a80: 494d 2d56 6c37 6d2d 5570 7364 2d4e 7966 IM-Vl7m-Upsd-Nyf
00001a90: 636a 7722 0a73 7461 7475 7320 3d20 5b22 cjw".status = ["
00001aa0: 5245 4144 222c 2022 5752 4954 4522 2c20 READ", "WRITE",
00001ab0: 2256 4953 4942 4c45 225d 0a66 6c61 6773 "VISIBLE"].flags
00001ac0: 203d 205b 5d0a 7365 676d 656e 745f 636f = [].segment_co
00001ad0: 756e 7420 3d20 310a 0a73 6567 6d65 6e74 unt = 1..segment
00001ae0: 3120 7b0a 7374 6172 745f 6578 7465 6e74 1 {.start_extent
00001af0: 203d 2030 0a65 7874 656e 745f 636f 756e = 0.extent_coun
00001b00: 7420 3d20 3131 390a 0a74 7970 6520 3d20 t = 119..type =
00001b10: 2273 7472 6970 6564 220a 7374 7269 7065 "striped".stripe
00001b20: 5f63 6f75 6e74 203d 2031 0923 206c 696e _count = 1.# lin
00001b30: 6561 720a 0a73 7472 6970 6573 203d 205b ear..stripes = [
00001b40: 0a22 7076 3022 2c20 3233 3739 0a5d 0a7d ."pv0", 2379.].}
00001b50: 0a7d 0a7d 0a7d 0a23 2047 656e 6572 6174 .}.}.}.# Generat
00001b60: 6564 2062 7920 4c56 4d32 2076 6572 7369 ed by LVM2 versi
00001b70: 6f6e 2032 2e30 322e 3534 2831 2920 2832 on 2.02.54(1) (2
00001b80: 3030 392d 3130 2d32 3629 3a20 4d6f 6e20 009-10-26): Mon
00001b90: 4170 7220 3234 2030 383a 3534 3a32 3220 Apr 24 08:54:22
00001ba0: 3230 3137 0a0a 636f 6e74 656e 7473 203d 2017..contents =
00001bb0: 2022 5465 7874 2046 6f72 6d61 7420 566f "Text Format Vo
00001bc0: 6c75 6d65 2047 726f 7570 220a 7665 7273 lume Group".vers
00001bd0: 696f 6e20 3d20 310a 0a64 6573 6372 6970 ion = 1..descrip
00001be0: 7469 6f6e 203d 2022 220a 0a63 7265 6174 tion = ""..creat
00001bf0: 696f 6e5f 686f 7374 203d 2022 7562 756e ion_host = "ubun
00001c00: 7475 2209 2320 4c69 6e75 7820 7562 756e tu".# Linux ubun
00001c10: 7475 2032 2e36 2e33 322d 3231 2d67 656e tu 2.6.32-21-gen
00001c20: 6572 6963 2023 3332 2d55 6275 6e74 7520 eric #32-Ubuntu
00001c30: 534d 5020 4672 6920 4170 7220 3136 2030 SMP Fri Apr 16 0
00001c40: 383a 3130 3a30 3220 5554 4320 3230 3130 8:10:02 UTC 2010
00001c50: 2069 3638 360a 6372 6561 7469 6f6e 5f74 i686.creation_t
00001c60: 696d 6520 3d20 3134 3933 3032 3430 3632 ime = 1493024062
00001c70: 0923 204d 6f6e 2041 7072 2032 3420 3038 .# Mon Apr 24 08
00001c80: 3a35 343a 3232 2032 3031 370a 0a00 0000 :54:22 2017.....
00001c90: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001ca0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001cb0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001cc0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001cd0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001ce0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001cf0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001d00: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001d10: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001d20: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001d30: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001d40: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001d50: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001d60: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001d70: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001d80: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001d90: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001da0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001db0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001dc0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001dd0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001de0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00001df0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
...
MBR的引导代码
提取引导代码
因为引导代码也是MBR的一部分，因此，调整提取MBR的命令即可提取之到文件，而后反编译之
dd if=path_to_your_disc bs=1 count=446 > path_to_mbr_code.bin
objdump -D -b binary -m i386 -Maddr16,data16 --adjust-vma=0x7c00 path_to_mbr_code.bin
# if you like the intel style
objdump -D -b binary -m i386 -Maddr16,data16,intel --adjust-vma=0x7c00 path_to_mbr_code.bin看看效果
一睹真实引导代码风采
现在的引导代码并非只是简单的一段实模式下的二进制程序，因此反编译的结果就差强人意了。如果你想一睹真实代码风貌，请看grub-core/boot/i386/pc/boot.S文件内容
/* -*-Asm-*- */
/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 1999,2000,2001,2002,2005,2006,2007,2008,2009 Free Software Foundation, Inc.
*
* GRUB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GRUB is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
*/
#include <grub/symbol.h>
#include <grub/machine/boot.h>
/*
* defines for the code go here
*/
/* Print message string */
#define MSG(x) movw $x, %si; call LOCAL(message)
#define ERR(x) movw $x, %si; jmp LOCAL(error_message)
.macro floppy
part_start:
LOCAL(probe_values):
.byte 36, 18, 15, 9, 0
LOCAL(floppy_probe):
pushw %dx
/*
* Perform floppy probe.
*/
#ifdef __APPLE__
LOCAL(probe_values_minus_one) = LOCAL(probe_values) - 1
movw MACRO_DOLLAR(LOCAL(probe_values_minus_one)), %si
#else
movw MACRO_DOLLAR(LOCAL(probe_values)) - 1, %si
#endif
LOCAL(probe_loop):
/* reset floppy controller INT 13h AH=0 */
xorw %ax, %ax
int MACRO_DOLLAR(0x13)
incw %si
movb (%si), %cl
/* if number of sectors is 0, display error and die */
testb %cl, %cl
jnz 1f
/*
* Floppy disk probe failure.
*/
MSG(fd_probe_error_string)
jmp LOCAL(general_error)
/* "Floppy" */
fd_probe_error_string: .asciz "Floppy"
1:
/* perform read */
movw MACRO_DOLLAR(GRUB_BOOT_MACHINE_BUFFER_SEG), %bx
movw %bx, %es
xorw %bx, %bx
movw MACRO_DOLLAR(0x201), %ax
movb MACRO_DOLLAR(0), %ch
movb MACRO_DOLLAR(0), %dh
int MACRO_DOLLAR(0x13)
/* if error, jump to "LOCAL(probe_loop)" */
jc LOCAL(probe_loop)
/* %cl is already the correct value! */
movb MACRO_DOLLAR(1), %dh
movb MACRO_DOLLAR(79), %ch
jmp LOCAL(final_init)
.endm
.macro scratch
/* scratch space */
mode:
.byte 0
disk_address_packet:
sectors:
.long 0
heads:
.long 0
cylinders:
.word 0
sector_start:
.byte 0
head_start:
.byte 0
cylinder_start:
.word 0
/* more space... */
.endm
.file "boot.S"
.text
/* Tell GAS to generate 16-bit instructions so that this code works
in real mode. */
.code16
.globl _start, start;
_start:
start:
/*
* _start is loaded at 0x7c00 and is jumped to with CS:IP 0:0x7c00
*/
/*
* Beginning of the sector is compatible with the FAT/HPFS BIOS
* parameter block.
*/
jmp LOCAL(after_BPB)
nop /* do I care about this ??? */
#ifdef HYBRID_BOOT
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
jmp LOCAL(after_BPB)
#else
/*
* This space is for the BIOS parameter block!!!! Don't change
* the first jump, nor start the code anywhere but right after
* this area.
*/
.org GRUB_BOOT_MACHINE_BPB_START
.org 4
#endif
#ifdef HYBRID_BOOT
floppy
#else
scratch
#endif
.org GRUB_BOOT_MACHINE_BPB_END
/*
* End of BIOS parameter block.
*/
LOCAL(kernel_address):
.word GRUB_BOOT_MACHINE_KERNEL_ADDR
#ifndef HYBRID_BOOT
.org GRUB_BOOT_MACHINE_KERNEL_SECTOR
LOCAL(kernel_sector):
.long 1
LOCAL(kernel_sector_high):
.long 0
#endif
.org GRUB_BOOT_MACHINE_BOOT_DRIVE
boot_drive:
.byte 0xff /* the disk to load kernel from */
/* 0xff means use the boot drive */
LOCAL(after_BPB):
/* general setup */
cli /* we're not safe here! */
/*
* This is a workaround for buggy BIOSes which don't pass boot
* drive correctly. If GRUB is installed into a HDD, check if
* DL is masked correctly. If not, assume that the BIOS passed
* a bogus value and set DL to 0x80, since this is the only
* possible boot drive. If GRUB is installed into a floppy,
* this does nothing (only jump).
*/
.org GRUB_BOOT_MACHINE_DRIVE_CHECK
boot_drive_check:
jmp 3f /* grub-setup may overwrite this jump */
testb $0x80, %dl
jz 2f
3:
/* Ignore %dl different from 0-0x0f and 0x80-0x8f. */
testb $0x70, %dl
jz 1f
2:
movb $0x80, %dl
1:
/*
* ljmp to the next instruction because some bogus BIOSes
* jump to 07C0:0000 instead of 0000:7C00.
*/
ljmp $0, $real_start
real_start:
/* set up %ds and %ss as offset from 0 */
xorw %ax, %ax
movw %ax, %ds
movw %ax, %ss
/* set up the REAL stack */
movw $GRUB_BOOT_MACHINE_STACK_SEG, %sp
sti /* we're safe again */
/*
* Check if we have a forced disk reference here
*/
movb boot_drive, %al
cmpb $0xff, %al
je 1f
movb %al, %dl
1:
/* save drive reference first thing! */
pushw %dx
/* print a notification message on the screen */
MSG(notification_string)
/* set %si to the disk address packet */
movw $disk_address_packet, %si
/* check if LBA is supported */
movb $0x41, %ah
movw $0x55aa, %bx
int $0x13
/*
* %dl may have been clobbered by INT 13, AH=41H.
* This happens, for example, with AST BIOS 1.04.
*/
popw %dx
pushw %dx
/* use CHS if fails */
jc LOCAL(chs_mode)
cmpw $0xaa55, %bx
jne LOCAL(chs_mode)
andw $1, %cx
jz LOCAL(chs_mode)
LOCAL(lba_mode):
xorw %ax, %ax
movw %ax, 4(%si)
incw %ax
/* set the mode to non-zero */
movb %al, -1(%si)
/* the blocks */
movw %ax, 2(%si)
/* the size and the reserved byte */
movw $0x0010, (%si)
/* the absolute address */
movl LOCAL(kernel_sector), %ebx
movl %ebx, 8(%si)
movl LOCAL(kernel_sector_high), %ebx
movl %ebx, 12(%si)
/* the segment of buffer address */
movw $GRUB_BOOT_MACHINE_BUFFER_SEG, 6(%si)
/*
* BIOS call "INT 0x13 Function 0x42" to read sectors from disk into memory
* Call with %ah = 0x42
* %dl = drive number
* %ds:%si = segment:offset of disk address packet
* Return:
* %al = 0x0 on success; err code on failure
*/
movb $0x42, %ah
int $0x13
/* LBA read is not supported, so fallback to CHS. */
jc LOCAL(chs_mode)
movw $GRUB_BOOT_MACHINE_BUFFER_SEG, %bx
jmp LOCAL(copy_buffer)
LOCAL(chs_mode):
/*
* Determine the hard disk geometry from the BIOS!
* We do this first, so that LS-120 IDE floppies work correctly.
*/
movb $8, %ah
int $0x13
jnc LOCAL(final_init)
popw %dx
/*
* The call failed, so maybe use the floppy probe instead.
*/
testb %dl, %dl
jnb LOCAL(floppy_probe)
/* Nope, we definitely have a hard disk, and we're screwed. */
ERR(hd_probe_error_string)
LOCAL(final_init):
/* set the mode to zero */
movzbl %dh, %eax
movb %ah, -1(%si)
/* save number of heads */
incw %ax
movl %eax, 4(%si)
movzbw %cl, %dx
shlw $2, %dx
movb %ch, %al
movb %dh, %ah
/* save number of cylinders */
incw %ax
movw %ax, 8(%si)
movzbw %dl, %ax
shrb $2, %al
/* save number of sectors */
movl %eax, (%si)
setup_sectors:
/* load logical sector start (top half) */
movl LOCAL(kernel_sector_high), %eax
orl %eax, %eax
jnz LOCAL(geometry_error)
/* load logical sector start (bottom half) */
movl LOCAL(kernel_sector), %eax
/* zero %edx */
xorl %edx, %edx
/* divide by number of sectors */
divl (%si)
/* save sector start */
movb %dl, %cl
xorw %dx, %dx /* zero %edx */
divl 4(%si) /* divide by number of heads */
/* do we need too many cylinders? */
cmpw 8(%si), %ax
jge LOCAL(geometry_error)
/* normalize sector start (1-based) */
incb %cl
/* low bits of cylinder start */
movb %al, %ch
/* high bits of cylinder start */
xorb %al, %al
shrw $2, %ax
orb %al, %cl
/* save head start */
movb %dl, %al
/* restore %dl */
popw %dx
/* head start */
movb %al, %dh
/*
* BIOS call "INT 0x13 Function 0x2" to read sectors from disk into memory
* Call with %ah = 0x2
* %al = number of sectors
* %ch = cylinder
* %cl = sector (bits 6-7 are high bits of "cylinder")
* %dh = head
* %dl = drive (0x80 for hard disk, 0x0 for floppy disk)
* %es:%bx = segment:offset of buffer
* Return:
* %al = 0x0 on success; err code on failure
*/
movw $GRUB_BOOT_MACHINE_BUFFER_SEG, %bx
movw %bx, %es /* load %es segment with disk buffer */
xorw %bx, %bx /* %bx = 0, put it at 0 in the segment */
movw $0x0201, %ax /* function 2 */
int $0x13
jc LOCAL(read_error)
movw %es, %bx
LOCAL(copy_buffer):
/*
* We need to save %cx and %si because the startup code in
* kernel uses them without initializing them.
*/
pusha
pushw %ds
movw $0x100, %cx
movw %bx, %ds
xorw %si, %si
movw $GRUB_BOOT_MACHINE_KERNEL_ADDR, %di
movw %si, %es
cld
rep
movsw
popw %ds
popa
/* boot kernel */
jmp *(LOCAL(kernel_address))
/* END OF MAIN LOOP */
/*
* BIOS Geometry translation error (past the end of the disk geometry!).
*/
LOCAL(geometry_error):
ERR(geometry_error_string)
/*
* Read error on the disk.
*/
LOCAL(read_error):
movw $read_error_string, %si
LOCAL(error_message):
call LOCAL(message)
LOCAL(general_error):
MSG(general_error_string)
/* go here when you need to stop the machine hard after an error condition */
/* tell the BIOS a boot failure, which may result in no effect */
int $0x18
LOCAL(stop):
jmp LOCAL(stop)
notification_string: .asciz "GRUB "
geometry_error_string: .asciz "Geom"
hd_probe_error_string: .asciz "Hard Disk"
read_error_string: .asciz "Read"
general_error_string: .asciz " Error\r\n"
/*
* message: write the string pointed to by %si
*
* WARNING: trashes %si, %ax, and %bx
*/
/*
* Use BIOS "int 10H Function 0Eh" to write character in teletype mode
* %ah = 0xe %al = character
* %bh = page %bl = foreground color (graphics modes)
*/
1:
movw $0x0001, %bx
movb $0xe, %ah
int $0x10 /* display a byte */
LOCAL(message):
lodsb
cmpb $0, %al
jne 1b /* if not end of string, jmp to display */
ret
/*
* Windows NT breaks compatibility by embedding a magic
* number here.
*/
#ifdef HYBRID_BOOT
.org 0x1b0
LOCAL(kernel_sector):
.long 1
LOCAL(kernel_sector_high):
.long 0
#endif
.org GRUB_BOOT_MACHINE_WINDOWS_NT_MAGIC
nt_magic:
.long 0
.word 0
/*
* This is where an MBR would go if on a hard disk. The code
* here isn't even referenced unless we're on a floppy. Kinda
* sneaky, huh?
*/
.org GRUB_BOOT_MACHINE_PART_START
#ifndef HYBRID_BOOT
floppy
#else
scratch
#endif
.org GRUB_BOOT_MACHINE_PART_END
/* the last 2 bytes in the sector 0 contain the signature */
.word GRUB_BOOT_MACHINE_SIGNATURE