dm-crypt/Encrypting a non-root file system
$ lsblk
$ wipefs -a /dev/sdb
# quick wipe target device
$ pvcreate /dev/sdb
$ pvs
$ vgs
$ vgextend ubuntu-vg /dev/sdb
$ vgs
$ lvs
$ lvcreate -n secret -L 10G ubuntu-vg
$ lvs
$ cryptsetup luksFormat /dev/ubuntu-vg/secret
# take a time
$ cryptsetup luksOpen /dev/ubuntu-vg/secret secret
# password
$ mkfs.ext4 /dev/mapper/secret
$ mkdir /secret # on / not /mnt/
$ mount /dev/mapper/secret /secret/
$ mount | grep secret
$ df -h /secret/
$ blkid -t TYPE=crypto_LUKS -o device
# to list LUKS devices
$ cryptsetup status secret
$ umount /secret
$ cryptsetup luksClose secret
$ lvextend -L +10G /dev/ubuntu-vg/secret
$ lvs
$ cryptsetup luksOpen /dev/ubuntu-vg/secret secret
# password
$ cryptsetup status secret
$ e2fsck -f /dev/mapper/secret
$ resize2fs -p /dev/mapper/secret
$ mount /dev/mapper/secret /secret/
$ df -h /secret/
fsarchiver
or just rsync -rauvlPL