First: yes, this was stupid, I know
A couple weeks ago I set up a new Ubuntu 18.04 machine, and included full disk encryption. It's been running since then, just locked at night. Today I was about to reboot it to update some software, and realized I wasn't entirely certain what the boot password is. (Well, at first I was certain I didn't remember it, but now I think I've remembered it.) Still, I'd like to be sure before I reboot.
I saw a post that said that
ecryptfs-unwrap-passphrase should get me the information, but running it (with or without sudo) gets me a
stat: no such file or directory error. I've found a video that shows me how to extract the master key and add a new passphrase, but I worry I'll screw something up and have to start over anyway.