Published 10 months ago.
Last updated August 22nd, 2024

Generate a new local SSH key-pair with ssh-keygen -t ed25519 -C "<your-github-account-email>" for use with github. Just hit return to use the default key-file name. Do not enter a passphrase (just hit return) unless you want to type a passphrase every time you commit.

$ ssh-keygen -t ed25519 -C "mrwattz@gmail.com"
Generating public/private ed25519 key pair.
Enter file in which to save the key (/Users/daniel/.ssh/id_ed25519): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /Users/daniel/.ssh/id_ed25519
Your public key has been saved in /Users/daniel/.ssh/id_ed25519.pub
The key fingerprint is:
SHA256:vO8SE+sfMY4/0IzFi/1n3F4rjjm5RcNf4ymHFdBC/og mrwattz@gmail.com
The key's randomart image is:
+--[ED25519 256]--+
|       +=+.     o|
|       .o+o    E.|
|        ..o.  . O|
|         . oo .=B|
|        S +o oo**|
|         .+ o.==+|
|         . +.o=..|
|        o. .oo.o |
|       o. ...o+. |
+----[SHA256]-----+

Check that the key files exist with ls -l ~/.ssh.

$ ls -l ~/.ssh
total 24
-rw-------  1 daniel  staff  411 Aug  3 13:53 id_ed25519
-rw-r--r--  1 daniel  staff   99 Aug  3 13:53 id_ed25519.pub
-rw-r--r--  1 daniel  staff  305 Aug  3 10:43 known_hosts

Check for the ssh configs file.

$ cat ~/.ssh/config
cat: /Users/daniel/.ssh/config: No such file or directory

If no .ssh/config file exists, create it.

$ touch ~/.ssh/config

Edit the .ssh/config file. Add the following content. Make sure the IdentityFile ssh configuration parameter points to your PRIVATE ssh key located at ~/.ssh/id_ed25519.

$ nano ~/.ssh/config
Host github.com
  HostName github.com
  User git
  AddKeysToAgent yes
  IdentityFile ~/.ssh/id_ed25519
  IdentitiesOnly yes

From https://wiki.ucar.edu/display/ral/Git+and+GitHub:

• If you have an ssh-agent loaded with keys, connecting to github.com may indeterminately use one of the keys in the agent, possibly using the WRONG key. Thus the IdentitiesOnly ssh configuration parameter must be set to yes in order to only use that Identity.

• GitHub does not support Usernames in ssh connections -- All connections use the username 'git', thus the User git ssh configuration parameter.

Make sure everything in the .ssh/config file looks good using cat ~/.ssh/config.

$ cat ~/.ssh/config
Host github.com
  HostName github.com
  User git
  AddKeysToAgent yes
  IdentityFile ~/.ssh/id_ed25519
  IdentitiesOnly yes

Start the ssh-agent app in the background, so we can add the new private key to it with eval "$(ssh-agent -s)".

$ eval "$(ssh-agent -s)"
Agent pid 45799

Add the private key file to the ssh-agent with ssh-add ~/.ssh/id_ed25519.

$ ssh-add ~/.ssh/id_ed25519
Identity added: /Users/daniel/.ssh/id_ed25519 (mrwattz@gmail.com)

Add the Public SSH Key to Your Github Account

View the content of the public SSH key with cat ~/.ssh/id_ed25519.pub.

dwatts@ral-venus:~$ cat ~/.ssh/id_ed25519.pub
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIIwUefbpKsVBURfNFEmzaFH9AS9c9ejgWR8FQg/Z22Bi mrwattz@gmail.com

Copy the file contents and it to your github user accounts SSH Keys section at: https://github.com/settings/keys

You need to add the key two times, once as the Authentication key and again for the Signing key. Make sure to title the keys so you know what server they are for.

The server should now be setup with your git user and ready to roll!