Steps to enable SSH with pubkey-auth.

Enable sshd

• On the Steam Deck, switch to Desktop Mode

• Open a terminal

• Set a user password with passwd so we can do superuser stuff

• Enable the ssh daemon with sudo systemctl start sshd

• Execute ip a to determine the IP address of the Steam Deck or use the hostname to connect to it

Prepare SSH key

• If no key exists yet, execute ssh-keygen on the host machine and follow the instructions to create a public/private key pair

• When using default settings, the files will be placed under ~/.ssh/

• Copy the content of ~/.ssh/id_rsa.pub, e.g. cat ~/.ssh/id_rsa.pub | pbcopy

Enable pubkey-auth

• Connect to the Steam Deck via SSH, e.g. ssh [email protected]

• Execute mkdir -p ~/.ssh/; nano ~/.ssh/authorized_keys

• Paste the content of the public key

• Press Ctrl+X and then Y to save and close the editor

• Enter exit to disconnect

• Check if pubkey-auth is working: Reconnect via SSH and it should not prompt for the user password.

SSHD hardening

• Open the sshd config file, e.g. sudo nano /etc/ssh/sshd_config

• Use Ctrl+W to search

• Disable root user login: Find and set PermitRootLogin to no

• Disable password login: Find and set PasswordAuthentication to no

• Press Ctrl+X and then Y to save and close the editor

• Restart sshd with sudo systemctl restart sshd

• Trying to login with root user or any username, e.g. ssh [email protected] should instantly fail showing Permission denied (publickey) without any password prompt