Which "features" of ext4 existing ext4 partition uses?

Question

When I create ext4 filesystem, there are many "features", which I can enable and disable - like has_journal, extent, huge_file and so on. Is there any way to know, which options were used while creating ext4 filesystem (after it been created, I mean)?

I have existed ext4 partition (created by somebody), but even don't know, did it use journal or extents.

Solution 1

I suppose you could use the dumpe2fs utility, to get a dump of ext2/etx3/ext4 filesystme informations.

For instance, something like this might do :

sudo dumpe2fs /dev/sda5 | more

ANd the beginning of the output looks like this, on my computer :

Last mounted on:          /
Filesystem UUID:          848446d9-a158-4442-905c-9a9551b0eb1a
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      has_journal ext_attr resize_inode dir_index filetype needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
Filesystem flags:         signed_directory_hash
Default mount options:    (none)
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              732960
Block count:              2929846
Reserved block count:     146492
...

Solution 2

You can use tune2fs to list out:

$ su -c "tune2fs -l /dev/sda6" | grep features
Password:
Filesystem features:      has_journal ext_attr resize_inode dir_index filetype needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
$

Solution 3

A simple way to get only what you need is using debugfs to query 'features' used in filesystem

sudo debugfs -R features /dev/sda5
Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery sparse_super large_file