In this tutorial, I will go through 8 dumpe2fs command examples to manage ext2, ext3 and ext4 filesystem in Linux. dumpe2fs is a very popular free and open source tool to check and manage the Linux based filesystems like ext2, ext3 and ext4. It can be used to check the detailed information of filesystems like UUID, magic number, free blocks, number of free inodes, currently set flags and many more. One can even check the information about corrupted filesystems using dumpe2fs utility.

What is Filesystem

It is an underlying data structure in Linux operating system responsible for storing and managing data storage on a disk partition in a specified manner.

Few of the Linux Filesystems

• EXT2 :  It is also Known as second extended filesystem in Linux Kernel. It inherited many features from BSD based Systems. It was once a very popular and default filesystem on Linux until it finally got replaced by ext3 filesystem.
• ETX3 : It is an extended version of ext2 filesystem with enhanced Journalling capabilities. It provides better protection of data and ensures the consistency within the filesystem state.
• EXT4 : It is the most commonly used Linux filesystem as of now. It is the scalable extension of ext3 filesystem and can support file and filesystems up to 16 TB in size. It also supports unlimited number of sub-directories as compared to ext3 filesystem which supports only up to 32,000.

Synopsis

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

dumpe2fs Command Examples to Manage EXT2, EXT3 and EXT4 Filesystem in Linux

Also Read: 7 Simple Steps to Install MTR(My Traceroute) on Linux(RHEL/CentOS 7/8)

Example 1: How to Check dumpe2fs Version in Linux

You can check dumpe2fs command version by using dumpe2fs -Version command as shown below. As you can see from below output, current version is 1.42.9

[root@localhost ~]# dumpe2fs -Version
dumpe2fs 1.42.9 (28-Dec-2013)
Using EXT2FS Library version 1.42.9

-Version : print the version number of dumpe2fs and exit. More on dumpe2fs Man Page.

Example 2: How to Only Display Superblock Information

If you want to display only the superblock information and not any of the block group descriptor detailed information then you need to use -h option with dumpe2fs command as shown below. In this example we are checking only the superblock information using dumpe2fs -h /dev/sdc1 command.

[root@localhost ~]# dumpe2fs -h /dev/sdc1
dumpe2fs 1.42.9 (28-Dec-2013)
Filesystem volume name: <none>
Last mounted on: <not available>
Filesystem UUID: 378a3ec4-3c5f-46b0-b5ca-18385d1ef00f
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent 64bit flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
Filesystem flags: signed_directory_hash
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 524288
Block count: 2096896
Reserved block count: 104844
Free blocks: 2022001
Free inodes: 524277
First block: 0
Block size: 4096
Fragment size: 4096
Group descriptor size: 64
Reserved GDT blocks: 1023

Example 3: How to Force dumpe2fs to display a filesystem in Linux

If you want to forcefully display a filesystem information even if the dumpe2fs does not understand the set filesystem flags then you need to use -f option with dumpe2fs command as shown below. In this example we are forcefully displaying /dev/sdc1 filesystem information using dumpe2fs -f /dev/sdc1 command as shown below.

[root@localhost ~]# dumpe2fs -f /dev/sdc1
dumpe2fs 1.42.9 (28-Dec-2013)
Filesystem volume name: <none>
Last mounted on: <not available>
Filesystem UUID: 378a3ec4-3c5f-46b0-b5ca-18385d1ef00f
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent 64bit flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize

Group 0: (Blocks 0-32767) [ITABLE_ZEROED]
Checksum 0xf155, unused inodes 8181
Primary superblock at 0, Group descriptors at 1-1
Reserved GDT blocks at 2-1024
Block bitmap at 1025 (+1025), Inode bitmap at 1041 (+1041)
Inode table at 1057-1568 (+1057)
23513 free blocks, 8181 free inodes, 2 directories, 8181 unused inodes
Free blocks: 9255-32767
Free inodes: 12-8192
Group 1: (Blocks 32768-65535) [INODE_UNINIT, ITABLE_ZEROED]
Checksum 0x0235, unused inodes 8192
Backup superblock at 32768, Group descriptors at 32769-32769
Reserved GDT blocks at 32770-33792
Block bitmap at 1026 (bg #0 + 1026), Inode bitmap at 1042 (bg #0 + 1042)
Inode table at 1569-2080 (bg #0 + 1569)
31743 free blocks, 8192 free inodes, 0 directories, 8192 unused inodes
Free blocks: 33793-65535
Free inodes: 8193-16384
Group 2: (Blocks 65536-98303) [INODE_UNINIT, BLOCK_UNINIT, ITABLE_ZEROED]
Checksum 0x9917, unused inodes 8192
Block bitmap at 1027 (bg #0 + 1027), Inode bitmap at 1043 (bg #0 + 1043)
Inode table at 2081-2592 (bg #0 + 2081)
32768 free blocks, 8192 free inodes, 0 directories, 8192 unused inodes
Free blocks: 65536-98303
Free inodes: 16385-24576

-f : force dumpe2fs to display a filesystem even though it may have some filesystem feature flags which dumpe2fs may not understand. More on dumpe2fs Man Page.

Example 4: How to Display dumpe2fs command output in Hexadecimal

If you want to display output in hexadecimal format then you need to use -x option with dumpe2fs command. In this example we are displaying the output of /dev/sdc1 partition filesystem information in hexadecimal format using dumpe2fs -x /dev/sdc1 command as shown below.

[root@localhost ~]# dumpe2fs -x /dev/sdc1
dumpe2fs 1.42.9 (28-Dec-2013)
Filesystem volume name: <none>
Last mounted on: <not available>
Default directory hash: half_md4
Directory Hash Seed: 2e4ecb7d-91af-41ac-b0e1-15e19aa05eef
Journal backup: inode blocks
Journal features: journal_64bit
Journal size: 128M
Journal length: 32768
Journal sequence: 0x00000005
Journal start: 0

Group 0: (Blocks 0x00000000-0x00007fff) [ITABLE_ZEROED]
Checksum 0xf155, unused inodes 8181
Primary superblock at 0x00000000, Group descriptors at 0x00000001-0x00000001
Reserved GDT blocks at 0x00000002-0x00000400
Block bitmap at 0x00000401 (+1025), Inode bitmap at 0x00000411 (+1041)
Inode table at 0x00000421-0x00000620 (+1057)
23513 free blocks, 8181 free inodes, 2 directories, 8181 unused inodes
Free blocks: 0x00002427-0x00007fff
Free inodes: 0x0000000c-0x00002000
Group 1: (Blocks 0x00008000-0x0000ffff) [INODE_UNINIT, ITABLE_ZEROED]
Checksum 0x0235, unused inodes 8192
Backup superblock at 0x00008000, Group descriptors at 0x00008001-0x00008001
Reserved GDT blocks at 0x00008002-0x00008400
Block bitmap at 0x00000402 (bg #0 + 1026), Inode bitmap at 0x00000412 (bg #0 + 1042)
Inode table at 0x00000621-0x00000820 (bg #0 + 1569)
31743 free blocks, 8192 free inodes, 0 directories, 8192 unused inodes
Free blocks: 0x00008401-0x0000ffff
Free inodes: 0x00002001-0x00004000

-x : print the detailed group information block numbers in hexadecimal format. More on dumpe2fs Man Page.

Example 5: How to Get All Backup Superblock Information of a Filesystem 

If you want to check all backup superblock information of a filesystem then you need to grep superblock keyword from dumpe2fs output. In this example we are checking backup superblock information of ext4 filesystem created on /dev/sdc1 partition using dumpe2fs /dev/sdc1 | grep -i superblock command as shown below.

[root@localhost ~]# dumpe2fs /dev/sdc1 | grep -i superblock
dumpe2fs 1.42.9 (28-Dec-2013)
Primary superblock at 0, Group descriptors at 1-1
Backup superblock at 32768, Group descriptors at 32769-32769
Backup superblock at 98304, Group descriptors at 98305-98305
Backup superblock at 163840, Group descriptors at 163841-163841
Backup superblock at 229376, Group descriptors at 229377-229377
Backup superblock at 294912, Group descriptors at 294913-294913
Backup superblock at 819200, Group descriptors at 819201-819201
Backup superblock at 884736, Group descriptors at 884737-884737
Backup superblock at 1605632, Group descriptors at 1605633-1605633

Example 6: How to Print Bad blocks in a Filesystem

If you want to print bad superblock in a filesystem then you need to use dumpe2fs -b /dev/sdc1 command as shown below. In this example, there are no bad blocks on /dev/sdc1 partition filesystem hence nothing is visible on the output.

[root@localhost ~]# dumpe2fs -b /dev/sdc1
dumpe2fs 1.42.9 (28-Dec-2013)

-b : print the blocks which are reserved as bad in the filesystem. More on dumpe2fs Man Page.

Example 7: How to Check all the available options of dumpe2fs Command in Linux

If you want to check all the available options of dumpe2fs command then you need to use dumpe2fs -h command as shown below.

[root@localhost ~]# dumpe2fs -h
dumpe2fs 1.42.9 (28-Dec-2013)
Usage: dumpe2fs [-bfhixV] [-o superblock=<num>] [-o blocksize=<num>] device

-h : only display the superblock information and not any of the block group descriptor detail information. More on dumpe2fs Man Page.

Example 8: How to Check Man Page of dumpe2fs Command in Linux

To check man page of dumpe2fs utility you need to use man dumpe2fs command as shown below.

[root@localhost ~]# man dumpe2fs
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 filesystem.

       -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.

 

 

 

 

 

 

 

 

 

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