云服务器 ECS Linux Super block 损坏修复方法是什么

Linux 分区 Super block 损坏，可以尝试手工修复，本文对此进行简要说明。
注意：操作有风险！操作前请务必先手工创建快照，防止数据丢失!




1、查找 super block 位置

1. $ dumpe2fs /dev/xvdb1 | grep --before-context=1 superblock
2. dumpe2fs 1.41.12 (17-May-2010)
3. Group 0: (Blocks 0-32767)
4.   Primary superblock at 0, Group descriptors at 1-1
5. --
6. Group 1: (Blocks 32768-65535)
7.   Backup superblock at 32768, Group descriptors at 32769-32769
8. --
9. Group 3: (Blocks 98304-131071)
10.   Backup superblock at 98304, Group descriptors at 98305-98305
11. --
12. Group 5: (Blocks 163840-196607)
13.   Backup superblock at 163840, Group descriptors at 163841-163841
14. --
15. Group 7: (Blocks 229376-262143)
16.   Backup superblock at 229376, Group descriptors at 229377-229377
17. --
18. Group 9: (Blocks 294912-327679)
19.   Backup superblock at 294912, Group descriptors at 294913-294913
20. --
21. Group 25: (Blocks 819200-851967)
22.   Backup superblock at 819200, Group descriptors at 819201-819201
23. --
24. Group 27: (Blocks 884736-917503)
25.   Backup superblock at 884736, Group descriptors at 884737-884737

1. 从上面操作可以看出，在第 1、3、5、7、9、25、27 这几个 Block Group 上存放有 superblock 备份。所以 super block 放置在如下这些块上（mke2fs -n /dev/xvdb1 可以更直观的显示出来）：
2. 32768, 98304, 163840, 229376, 294912, 819200, 884736

1. $ dd if=/dev/zero of=/dev/xvdb1 bs=1 count=1024 seek=1024
2. 1024+0 records in
3. 1024+0 records out
4. 1024 bytes (1.0 kB) copied, 0.00852143 s, 120 kB/s
6. 这时候我们根本无法从dumpe2fs和tune2fs看到Backup superblock的位置
7. $ dumpe2fs /dev/xvdb1 | grep --before-context=1 superblock
8. dumpe2fs 1.41.12 (17-May-2010)
9. dumpe2fs: Bad magic number in super-block while trying to open /dev/xvdb1
10. Couldn't find valid filesystem superblock.

1. $ mke2fs -S /dev/xvdb1
3. 可以看到已经修复
4. $ dumpe2fs /dev/xvdb1 | grep --before-context=1 superblock
5. dumpe2fs 1.41.12 (17-May-2010)
6. Group 0: (Blocks 0-32767)
7.   Primary superblock at 0, Group descriptors at 1-1
8. --
9. Group 1: (Blocks 32768-65535)
10.   Backup superblock at 32768, Group descriptors at 32769-32769
11. --
12. Group 3: (Blocks 98304-131071)
13.   Backup superblock at 98304, Group descriptors at 98305-98305
14. --
15. Group 5: (Blocks 163840-196607)
16.   Backup superblock at 163840, Group descriptors at 163841-163841
17. --
18. Group 7: (Blocks 229376-262143)
19.   Backup superblock at 229376, Group descriptors at 229377-229377
20. --
21. Group 9: (Blocks 294912-327679)
22.   Backup superblock at 294912, Group descriptors at 294913-294913
23. --
24. Group 25: (Blocks 819200-851967)
25.   Backup superblock at 819200, Group descriptors at 819201-819201
26. --
27. Group 27: (Blocks 884736-917503)
28.   Backup superblock at 884736, Group descriptors at 884737-884737

1. $ dd if=/dev/zero of=/dev/xvdb1 bs=1 count=1024 seek=1024
2. $ e2fsck /dev/xvdb1
4. 或者
5. $ e2fsck -b 884736 /dev/xvdb1            
6. # 放置备份的super block的块