Enable dropbear on boot to decrypt full disk encryption

https://hamy.io/post/0009/how-to-install-luks-encrypted-ubuntu-18.04.x-server-and-enable-remote-unlocking/

install dropbear-initramfs

copy authorized_keys to /etc/dropbear/initramfs, prepend

no-port-forwarding,no-agent-forwarding,no-x11-forwarding,command="/bin/cryptroot-unlock" ssh-rsa ... 


- if DHCP no config neccesary

in  /etc/dropbear/initramfs/dropbear.conf

DROPBEAR_OPTIONS="-p 4789 -s -j -k -I 60"