This is a neat feature. During a Ubuntu 20.04.x installation the initial user can automatically retrieve
ssh keys from GitHub:
Right after installation,
ssh key authentication works as expected:
jemurray@mbp-2019:~ $ ssh 192.168.86.32 The authenticity of host '192.168.86.32 (192.168.86.32)' can't be established. ECDSA key fingerprint is SHA256:zd7aT9GlQV2qsONFr2fKrx86ULQvBicSKBo2mrnUnm8. Are you sure you want to continue connecting (yes/no/[fingerprint])? yes Warning: Permanently added '192.168.86.32' (ECDSA) to the list of known hosts. Welcome to Ubuntu 20.04.1 LTS (GNU/Linux 5.4.0-51-generic x86_64) * Documentation: https://help.ubuntu.com * Management: https://landscape.canonical.com * Support: https://ubuntu.com/advantage System information as of Wed Oct 14 20:15:43 UTC 2020 System load: 0.93 Usage of /: 25.1% of 23.99GB Memory usage: 1% Swap usage: 0% Processes: 270 Users logged in: 0 IPv4 address for ens160: 192.168.86.32 IPv6 address for ens160: 2600:1700:1391:411f:20c:29ff:fe28:bb6e 53 updates can be installed immediately. 0 of these updates are security updates. To see these additional updates run: apt list --upgradable Last login: Wed Oct 14 20:15:19 2020 To run a command as administrator (user "root"), use "sudo <command>". See "man sudo_root" for details.
They also disabled password authentication by default:
jemurray@home-server:~$ ssh 192.168.86.32 email@example.com: Permission denied (publickey).