fatal: unable to create lock in backend (restic)

While trying to forget a Restic snapshot, I encountered this error:

Fatal: unable to create lock in backend

I didn’t manually lock the repo, so this was strange. I suspect it’s because I terminated an active cron process and the processes didn’t exit gracefully. Anyway, fixing it was easy (oh my god, an easy victory for once). You simply run:

restic -r your-protocol:machine:/path/to/repo unlock

Fatal: unable to create lock in backend: repository is already locked by PID 38397