EXT4-fs (sda): couldn’t mount RDWR because of unsupported optional features (400)

I could be happen on EXT3 or EXT2 too. This error mean that there is enabled file system feature that does not supported by kernel.

I’ve got an error when I make EXT4 partition with e2fsprogs (mkfs.ext4) newer then my kernel.

First solution is create ext4 with oldertools:

apt-get remove e2fslibs e2fsprogs

and install older.
Second solution is remove features does not supported by kernel.
To list features run :

tune2fs -l /dev/sdaX

I’ve got:
Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file dir_nlink extra_isize metadata_csum
To try figure it out which feature is not supported you can try run

fsck /dev/sdaX
e2fsck -pv /dev/sdaX
mount /dev/sdaX /mountpoint
dmesg | tail

Remove them one by one because after some you have to fix file system and do other things:

tune2fs -O ^flex_bg /dev/sdaX

do something try mount

tune2fs -O ^metadata_csum /dev/sdaX

do something try mount

tune2fs -O ^extra_isize /dev/sdaX

do something try mount

tune2fs -O ^dir_nlink /dev/sdaX

do something try mount
Do something I mean fsck and other things which will be listed after command.
Done :)

1 Comment

  1. thanks, that helped me a lot. i created the filesystem with feature metadata_csum and 64bit. the 64bit can be removed with resize2fs -s. my rhel6 system supports ext4 but not those features.
    after that i had to boot from a rescue cd with a rhel/centos6 and doing a fsck.ext4 on it and fix the superblock. because one of those not supported features couldnt be removed with tune2fs, just with an older fsck.ext4 version.

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