Which "features" of ext4 existing ext4 partition uses?

Solution 1:

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 2:

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 3:

You can use file -s $DEVICE which outputs on my system:

# /dev/dm-0: Linux rev 1.0 ext4 filesystem data (needs journal recovery) (extents) (large files) (huge files)