xubuntu@xubuntu:~$ sudo mke2fs -n  /dev/mapper/luks-79a5cf84-516e-4783-b464-09b00d08a724
mke2fs 1.42.13 (17-May-2015)
/dev/mapper/luks-79a5cf84-516e-4783-b464-09b00d08a724 contains a zfs_member file system labelled 'rpool'
Proceed anyway? (y,n) y
Creating filesystem with 488249856 4k blocks and 122068992 inodes
Filesystem UUID: ace21e20-b1a5-49ea-8cc7-2a22700ae592
Superblock backups stored on blocks: 
	32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
	4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968, 
	102400000, 214990848

xubuntu@xubuntu:~$