1. 创建一个XFS文件系统
[root@localhost ~]# mkfs.xfs -f /dev/vdb1
meta-data=/dev/vdb1              isize=256    agcount=4, agsize=1966102 blks
        =                       sectsz=512   attr=2, projid32bit=0
data     =                       bsize=4096   blocks=7864408, imaxpct=25
        =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0
log      =internal log           bsize=4096   blocks=3840, version=2
        =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

[root@localhost ~]# cat /etc/fstab |grep vdb1
/dev/vdb1     /test     xfs     defaults     0 0

[root@localhost ~]# mount -a

[root@localhost ~]# df -h
/dev/vdb1                         30G  610M   30G   2% /test

2. 卸载文件系统/test, 并且破坏superblock
[root@localhost ~]# umount /test

[root@localhost ~]# dd if=/dev/zero of=/dev/vdb1 bs=512 count=1
1+0 records in
1+0 records out
512 bytes (512 B) copied, 0.00251096 s, 204 kB/s

3. 再次挂载报错
[root@localhost ~]# mount -a
mount: wrong fs type, bad option, bad superblock on /dev/vdb1,
      missing codepage or helper program, or other error
      In some cases useful info is found in syslog - try
      dmesg | tail  or so

[root@localhost ~]# dmesg
[22597379.623449] XFS (vdb1): bad magic number
[22597379.624372] XFS (vdb1): SB validate failed

4. 恢复superblock
[root@localhost ~]# xfs_repair /dev/vdb1
Phase 1 - find and verify superblock...
bad primary superblock - bad magic number !!!

attempting to find secondary superblock...
.........found candidate secondary superblock...
verified secondary superblock...
writing modified primary superblock
sb realtime bitmap inode 18446744073709551615 (NULLFSINO) inconsistent with calculated value 129
resetting superblock realtime bitmap ino pointer to 129
sb realtime summary inode 18446744073709551615 (NULLFSINO) inconsistent with calculated value 130
resetting superblock realtime summary ino pointer to 130
Phase 2 - using internal log
       - zero log...
       - scan filesystem freespace and inode maps...
sb_icount 0, counted 64
sb_ifree 0, counted 60
sb_fdblocks 7860552, counted 7712768
       - found root inode chunk
Phase 3 - for each AG...
       - scan and clear agi unlinked lists...
       - process known inodes and perform inode discovery...
       - agno = 0
       - agno = 1
       - agno = 2
       - agno = 3
       - process newly discovered inodes...
Phase 4 - check for duplicate blocks...
       - setting up duplicate extent list...
       - check for inodes claiming duplicate blocks...
       - agno = 0
       - agno = 1
       - agno = 2
       - agno = 3
Phase 5 - rebuild AG headers and trees...
       - reset superblock...
Phase 6 - check inode connectivity...
       - resetting contents of realtime bitmap and summary inodes
       - traversing filesystem ...
       - traversal finished ...
       - moving disconnected inodes to lost+found ...
Phase 7 - verify and correct link counts...
Note - stripe unit (0) and width (0) fields have been reset.
Please set with mount -o sunit=<value>,swidth=<value>
done

5. 确认是否已经恢复
[root@localhost ~]# mount -a
[root@localhost ~]# df -h
/dev/vdb1                         30G  610M   30G   2% /test