使用dumpe2fs 查看superblock的信息：
[root@localhost ~]# dumpe2fs /dev/sda1
dumpe2fs 1.39 (29-May-2006)
Filesystem volume name: /boot 文件系统名
Last mounted on: <not available>
Filesystem UUID: b20ffbe6-f56d-4eee-a3a2-22145aa88e36
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery sparse_super
Default mount options: user_xattr acl 预设挂载的参数
Filesystem state: clean 文件系统没问题
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 26104 inode总数
Block count: 104388 block总数
Reserved block count: 5219
Free blocks: 89087 剩余block
Free inodes: 26070 剩余inode
First block: 1
Block size: 1024 每个block大小
Fragment size: 1024
Reserved GDT blocks: 256
Blocks per group: 8192
Fragments per group: 8192
Inodes per group: 2008
Inode blocks per group: 251
Filesystem created: Tue Oct 21 15:21:01 2014
Last mount time: Wed Nov 5 09:55:55 2014
Last write time: Wed Nov 5 09:55:55 2014
Mount count: 19
Maximum mount count: -1
Last checked: Tue Oct 21 15:21:01 2014
Check interval: 0 (<none>)
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 128 每个inode大小
Journal inode: 8
Default directory hash: tea
Directory Hash Seed: 61428c96-2452-4c54-b4e4-21fe31cceb6b
Journal backup: inode blocks
Journal size: 4114k
Group 0: (Blocks 1-8192) 第一个data group 内容，包含block开始和结束号码
Primary superblock at 1, Group descriptors at 2-2
Reserved GDT blocks at 3-258
Block bitmap at 259 (+258), Inode bitmap at 260 (+259)
Inode table at 261-511 (+260)
479 free blocks, 1991 free inodes, 2 directories
Free blocks: 4642-5120
Free inodes: 18-2008
Group 1: (Blocks 8193-16384)
Backup superblock at 8193, Group descriptors at 8194-8194
Reserved GDT blocks at 8195-8450
Block bitmap at 8451 (+258), Inode bitmap at 8452 (+259)
Inode table at 8453-8703 (+260)
4420 free blocks, 1991 free inodes, 1 directories
Free blocks: 11808-12288, 12296-12800, 12810-13312, 13349-15360, 15362-15872, 15977-16384
Free inodes: 2026-4016
Group 2: (Blocks 16385-24576)
Block bitmap at 16385 (+0), Inode bitmap at 16386 (+1)
Inode table at 16387-16637 (+2)
7939 free blocks, 2008 free inodes, 0 directories
Free blocks: 16638-24576
Free inodes: 4017-6024
Group 3: (Blocks 24577-32768)
Backup superblock at 24577, Group descriptors at 24578-24578
Reserved GDT blocks at 24579-24834
Block bitmap at 24835 (+258), Inode bitmap at 24836 (+259)
Inode table at 24837-25087 (+260)
7681 free blocks, 2008 free inodes, 0 directories
Free blocks: 25088-32768
Free inodes: 6025-8032
Group 4: (Blocks 32769-40960)
Block bitmap at 32769 (+0), Inode bitmap at 32770 (+1)
Inode table at 32771-33021 (+2)
7939 free blocks, 2008 free inodes, 0 directories
Free blocks: 33022-40960
Free inodes: 8033-10040
Group 5: (Blocks 40961-49152)
Backup superblock at 40961, Group descriptors at 40962-40962
Reserved GDT blocks at 40963-41218
Block bitmap at 41219 (+258), Inode bitmap at 41220 (+259)
Inode table at 41221-41471 (+260)
7681 free blocks, 2008 free inodes, 0 directories
Free blocks: 41472-49152
Free inodes: 10041-12048
Group 6: (Blocks 49153-57344)
Block bitmap at 49153 (+0), Inode bitmap at 49154 (+1)
Inode table at 49155-49405 (+2)
7939 free blocks, 2008 free inodes, 0 directories
Free blocks: 49406-57344
Free inodes: 12049-14056
Group 7: (Blocks 57345-65536)
Backup superblock at 57345, Group descriptors at 57346-57346
Reserved GDT blocks at 57347-57602
Block bitmap at 57603 (+258), Inode bitmap at 57604 (+259)
Inode table at 57605-57855 (+260)
7681 free blocks, 2008 free inodes, 0 directories
Free blocks: 57856-65536
Free inodes: 14057-16064
Group 8: (Blocks 65537-73728)
Block bitmap at 65537 (+0), Inode bitmap at 65538 (+1)
Inode table at 65539-65789 (+2)
7939 free blocks, 2008 free inodes, 0 directories
Free blocks: 65790-73728
Free inodes: 16065-18072
Group 9: (Blocks 73729-81920)
Backup superblock at 73729, Group descriptors at 73730-73730
Reserved GDT blocks at 73731-73986
Block bitmap at 73987 (+258), Inode bitmap at 73988 (+259)
Inode table at 73989-74239 (+260)
7681 free blocks, 2008 free inodes, 0 directories
Free blocks: 74240-81920
Free inodes: 18073-20080
Group 10: (Blocks 81921-90112)
Block bitmap at 81921 (+0), Inode bitmap at 81922 (+1)
Inode table at 81923-82173 (+2)
7939 free blocks, 2008 free inodes, 0 directories
Free blocks: 82174-90112
Free inodes: 20081-22088
Group 11: (Blocks 90113-98304)
Block bitmap at 90113 (+0), Inode bitmap at 90114 (+1)
Inode table at 90115-90365 (+2)
7939 free blocks, 2008 free inodes, 0 directories
Free blocks: 90366-98304
Free inodes: 22089-24096
Group 12: (Blocks 98305-104387)
Block bitmap at 98305 (+0), Inode bitmap at 98306 (+1)
Inode table at 98307-98557 (+2)
5830 free blocks, 2008 free inodes, 0 directories
Free blocks: 98558-104387
Free inodes: 24097-26104
