I think there is no harm. Read this :- https://ext4.wiki.kernel.org/index.php/Frequently_Asked_Questions#Can_I_mount_existing_Ext3_as_Ext4.3F_And_vice_versa.3F_Similarly_from_Ext2_to_Ext4_and_its_reverse.3F Which says it is ok to mount ext2/ext3 as ext4. As long as you don't turn on the ext4 specific features, the file system remains as ext2.