xubuntu@xubuntu:~$ sudo mount -t ext4 /dev/mapper/luks-79a5cf84-516e-4783-b464-09b00d08a724 /mnt
mount: wrong fs type, bad option, bad superblock on /dev/mapper/luks-79a5cf84-516e-4783-b464-09b00d08a724,
       missing codepage or helper program, or other error

       In some cases useful info is found in syslog - try
       dmesg | tail or so.
xubuntu@xubuntu:~$