Resize encrypted LVM

lvm-crypt-resize.txt

IN SHORT:
0. increase size of outermost container (grow qcow2, dd disk to larger disk, etc.)
1. increase size of partition containing the encrypted volume set (cfdisk, fdisk, etc.)
2. unlock encrypted volume
3. grow LVM "physical volume"
4. grow LVM "logical volume"
5. check filesystem
6. grow filesystem
7. tidy up and test.

Steps on Debian:
[if qemu image, first on host system:]
qemu-img resize diskimage.qcow2 +50G

[then, within liveCD environment]
cfdisk /dev/sda - and grow the partition to fill the larger device
apt update && apt install -y lvm2 cryptsetup
modprobe dm-crypt
cryptsetup luksOpen /dev/sda3 aribtraryname
pvdisplay -m [note your device in the list - must be 'Allocatable: yes' - if not, see next line]
pvchange -x y /dev/mapper/arbitraryname
pvdisplay -m
pvresize /dev/mapper/arbitraryname
vgscan --mknodes
vgchange -ay
lvdisplay [note the names assigned to your volumes]
lvextend -l +100%FREE /dev/somethingelse/volumename
e2fsck -f /dev/somethingelse/volumename
resize2fs /dev/somethingelse/volumename
vgchange -an
cryptsetup luksClose arbitraryname