Let's say you have already generated an SSH key for GitHub, as instructed here:
https://docs.github.com/en/free-pro-team@latest/github/authenticating-to-github/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent
Now your .ssh folder will be like this:
PHS015945:.ssh xd010$ ll
-rw-r--r-- 1 xd010 staff 165B Dec 9 23:21 config
-rw------- 1 xd010 staff 411B Dec 9 23:12 id_ed25519
-rw-r--r-- 1 xd010 staff 100B Dec 9 23:12 id_ed25519.pub
where config file will be like:
Host *
AddKeysToAgent yes
UseKeychain yes
IdentityFile ~/.ssh/id_ed25519
Now, you want to ssh to your HPC server without a password. You will follow instructions like this http://www.linuxproblem.org/art_9.html, e.g.
a@A:~> ssh-keygen -t rsa Generating public/private rsa key pair. Enter file in which to save the key (/home/a/.ssh/id_rsa): Created directory '/home/a/.ssh'. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/a/.ssh/id_rsa. Your public key has been saved in /home/a/.ssh/id_rsa.pub. The key fingerprint is: 3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a@A
Now append a's new public key to b@B:.ssh/authorized_keys and enter b's password one last time:
a@A:~> cat .ssh/id_rsa.pub | ssh b@B 'cat >> .ssh/authorized_keys' b@B's password:
You will find that you are still asked to enter the password when you want to ssh to your HPC. Where's the problem?
