dumpe2fs - dump ext2/ext3/ext4 filesystem information

```
[root@xxxx linuxstudy]# dumpe2fs /dev/sdb1
dumpe2fs 1.42.9 (28-Dec-2013)
Filesystem volume name:   /usbmemory
Last mounted on:          /usbmemory2
Filesystem UUID:          45d9c0a6-98b7-4091-9d13-8e510b7738c8
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      ext_attr resize_inode dir_index filetype sparse_super large_file
Filesystem flags:         signed_directory_hash 
Default mount options:    user_xattr acl
Filesystem state:         not clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              65536
Block count:              262144
Reserved block count:     13107
Free blocks:              257700
Free inodes:              65523
First block:              0
Block size:               4096
Fragment size:            4096
Reserved GDT blocks:      63
Blocks per group:         32768
Fragments per group:      32768
Inodes per group:         8192
Inode blocks per group:   512
Filesystem created:       Thu Jun 29 20:36:58 2023
Last mount time:          Thu Feb  1 19:41:10 2024
Last write time:          Sun Feb 11 01:04:41 2024
Mount count:              23
Maximum mount count:      -1
Last checked:             Thu Jun 29 20:36:58 2023
Check interval:           1209600 (2 weeks)
Next check after:         Thu Jul 13 20:36:58 2023
Lifetime writes:          324 kB
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:	          256
Required extra isize:     28
Desired extra isize:      28
Default directory hash:   half_md4
Directory Hash Seed:      e7c76377-046d-4c27-8f6d-761d1819ae84


Group 0: (Blocks 0-32767)
  Primary superblock at 0, Group descriptors at 1-1
  Reserved GDT blocks at 2-64
  Block bitmap at 65 (+65), Inode bitmap at 66 (+66)
  Inode table at 67-578 (+67)
  32182 free blocks, 8179 free inodes, 3 directories
Group 1: (Blocks 32768-65535)
  Backup superblock at 32768, Group descriptors at 32769-32769
  Reserved GDT blocks at 32770-32832
  Block bitmap at 32833 (+65), Inode bitmap at 32834 (+66)
  Inode table at 32835-33346 (+67)
  32189 free blocks, 8192 free inodes, 0 directories
Group 2: (Blocks 65536-98303)
  Block bitmap at 65536 (+0), Inode bitmap at 65537 (+1)
  Inode table at 65538-66049 (+2)
  32254 free blocks, 8192 free inodes, 0 directories
Group 3: (Blocks 98304-131071)
  Backup superblock at 98304, Group descriptors at 98305-98305
  Reserved GDT blocks at 98306-98368
  Block bitmap at 98369 (+65), Inode bitmap at 98370 (+66)
  Inode table at 98371-98882 (+67)
  32189 free blocks, 8192 free inodes, 0 directories
Group 4: (Blocks 131072-163839)
  Block bitmap at 131072 (+0), Inode bitmap at 131073 (+1)
  Inode table at 131074-131585 (+2)
  32254 free blocks, 8192 free inodes, 0 directories
Group 5: (Blocks 163840-196607)
  Backup superblock at 163840, Group descriptors at 163841-163841
  Reserved GDT blocks at 163842-163904
  Block bitmap at 163905 (+65), Inode bitmap at 163906 (+66)
  Inode table at 163907-164418 (+67)
  32189 free blocks, 8192 free inodes, 0 directories
Group 6: (Blocks 196608-229375)
  Block bitmap at 196608 (+0), Inode bitmap at 196609 (+1)
  Inode table at 196610-197121 (+2)
  32254 free blocks, 8192 free inodes, 0 directories
Group 7: (Blocks 229376-262143)
  Backup superblock at 229376, Group descriptors at 229377-229377
  Reserved GDT blocks at 229378-229440
  Block bitmap at 229441 (+65), Inode bitmap at 229442 (+66)
  Inode table at 229443-229954 (+67)
  32189 free blocks, 8192 free inodes, 0 directories

dumpe2fs: /dev/sdb1: error reading bitmaps: Can't read a block bitmap
```
```
DUMPE2FS(8)                                                                                System Manager's Manual                                                                                DUMPE2FS(8)



NAME
       dumpe2fs - dump ext2/ext3/ext4 filesystem information

SYNOPSIS
       dumpe2fs [ -bfhixV ] [ -o superblock=superblock ] [ -o blocksize=blocksize ] device

DESCRIPTION
       dumpe2fs prints the super block and blocks group information for the filesystem present on device.

       Note: When used with a mounted filesystem, the printed information may be old or inconsistent.

OPTIONS
       -b     print the blocks which are reserved as bad in the filesystem.

       -o superblock=superblock
              use the block superblock when examining the filesystem.  This option is not usually needed except by a filesystem wizard who is examining the remains of a very badly corrupted filesystem.

       -o blocksize=blocksize
              use  blocks  of blocksize bytes when examining the filesystem.  This option is not usually needed except by a filesystem wizard who is examining the remains of a very badly corrupted filesys‐
              tem.

       -f     force dumpe2fs to display a filesystem even though it may have some filesystem feature flags which dumpe2fs may not understand (and which can cause some of dumpe2fs's display to be suspect).

       -h     only display the superblock information and not any of the block group descriptor detail information.

       -i     display the filesystem data from an image file created by e2image, using device as the pathname to the image file.

       -x     print the detailed group information block numbers in hexadecimal format

       -V     print the version number of dumpe2fs and exit.

BUGS
       You need to know the physical filesystem structure to understand the output.

AUTHOR
       dumpe2fs was written by Remy Card <Remy.Card@linux.org>.  It is currently being maintained by Theodore Ts'o <tytso@alum.mit.edu>.

AVAILABILITY
       dumpe2fs is part of the e2fsprogs package and is available from http://e2fsprogs.sourceforge.net.

SEE ALSO
       e2fsck(8), mke2fs(8), tune2fs(8).  ext4(5)




E2fsprogs version 1.42.9                                                                        December 2013                                                                                     DUMPE2FS(8)```