While hardening SSH on my home server I changed PasswordAuthentication no before copying my key. Instantly lost access.
What I ran:
sudo nano /etc/ssh/sshd_config
sudo systemctl restart sshd
The error:
ssh: connect to host limonlab.online port 22: Connection refused
How I fixed it: I had physical access to the laptop so I logged in directly and ran:
sudo systemctl status sshd
journalctl -u sshd -n 20
Found a syntax error in sshd_config. Fixed it, restarted, reconnected.
What I learned: Always test with sshd -t before restarting.