原文网址：https://www.youyong.top/article/1158e5bd41e6

1、查找 super block 位置

$ dumpe2fs /dev/xvdb1 | grep --before-context=1 superblock
dumpe2fs 1.41.12 (17-May-2010)
Group 0: (Blocks 0-32767)
  Primary superblock at 0, Group descriptors at 1-1
--
Group 1: (Blocks 32768-65535)
  Backup superblock at 32768, Group descriptors at 32769-32769
--
Group 3: (Blocks 98304-131071)
  Backup superblock at 98304, Group descriptors at 98305-98305
--
Group 5: (Blocks 163840-196607)
  Backup superblock at 163840, Group descriptors at 163841-163841
--
Group 7: (Blocks 229376-262143)
  Backup superblock at 229376, Group descriptors at 229377-229377
--
Group 9: (Blocks 294912-327679)
  Backup superblock at 294912, Group descriptors at 294913-294913
--
Group 25: (Blocks 819200-851967)
  Backup superblock at 819200, Group descriptors at 819201-819201
--
Group 27: (Blocks 884736-917503)
  Backup superblock at 884736, Group descriptors at 884737-884737

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）：
32768, 98304, 163840, 229376, 294912, 819200, 884736

2、破坏 super block 测试

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

3、mke2fs 方式修复示例

$ mke2fs -S /dev/xvdb1
可以看到已经修复
$ dumpe2fs /dev/xvdb1 | grep --before-context=1 superblock
dumpe2fs 1.41.12 (17-May-2010)
Group 0: (Blocks 0-32767)
  Primary superblock at 0, Group descriptors at 1-1
--
Group 1: (Blocks 32768-65535)
  Backup superblock at 32768, Group descriptors at 32769-32769
--
Group 3: (Blocks 98304-131071)
  Backup superblock at 98304, Group descriptors at 98305-98305
--
Group 5: (Blocks 163840-196607)
  Backup superblock at 163840, Group descriptors at 163841-163841
--
Group 7: (Blocks 229376-262143)
  Backup superblock at 229376, Group descriptors at 229377-229377
--
Group 9: (Blocks 294912-327679)
  Backup superblock at 294912, Group descriptors at 294913-294913
--
Group 25: (Blocks 819200-851967)
  Backup superblock at 819200, Group descriptors at 819201-819201
--
Group 27: (Blocks 884736-917503)
  Backup superblock at 884736, Group descriptors at 884737-884737

4、e2fsck 方式修复示例

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

原文网址：https://www.youyong.top/article/1158e5bd41e6