1e2fsck external journal
2../e2fsck/e2fsck: Filesystem has unsupported feature(s) while trying to open test.img
3
4The superblock could not be read or does not describe a valid ext2/ext3/ext4
5filesystem.  If the device is valid and it really contains an ext2/ext3/ext4
6filesystem (and not swap or ufs or something else), then the superblock
7is corrupt, and you might try running e2fsck with an alternate superblock:
8    e2fsck -b 8193 <device>
9 or
10    e2fsck -b 32768 <device>
11
12Exit status is 8
13dumpe2fs external journal
14Filesystem volume name:   <none>
15Last mounted on:          <not available>
16Filesystem magic number:  0xEF53
17Filesystem revision #:    1 (dynamic)
18Filesystem features:      journal_dev metadata_csum
19Default mount options:    user_xattr acl block_validity
20Filesystem state:         clean
21Errors behavior:          Continue
22Filesystem OS type:       Linux
23Inode count:              0
24Block count:              2048
25Reserved block count:     0
26Free blocks:              0
27Free inodes:              0
28First block:              1
29Block size:               1024
30Fragment size:            1024
31Blocks per group:         8192
32Fragments per group:      8192
33Inodes per group:         0
34Inode blocks per group:   0
35Mount count:              0
36Check interval:           0 (<none>)
37Reserved blocks uid:      0
38Reserved blocks gid:      0
39First inode:              11
40Inode size:	          256
41Required extra isize:     28
42Desired extra isize:      28
43Default directory hash:   half_md4
44Checksum type:            crc32c
45Journal features:         journal_64bit journal_checksum_v3
46Journal size:             2048k
47Journal length:           2048
48Journal first block:      3
49Journal sequence:         0x00000003
50Journal start:            0
51Journal checksum type:    crc32c
52Journal checksum:         0x661e816f
53Journal users:            117f752e-f27d-4f6f-a652-072586a29b82
54