Ah, you’re talking about LUKS. LVM is just the volume manager.

The standard way is to add an sshd (such as dropbear) to your initramfs so that you can ssh in and run commands (such as entering the root partition password) during system boot.

See:

https://unix.stackexchange.com/questions/5017/ssh-to-decrypt-encrypted-lvm-during-headless-server-boot

will that cause me problems on a headless server if I get a power outage and need to reboot? I think yes

Maybe I’m missing something obvious, but what is the problem that you anticipate with LVM after a power failure?

Thanks for posting this. I’ve been meaning to write something similar for a while but never got around to it. I wish Restic would ship an official client application for managing this stuff!