How to set up SSH and Github for multiple authenticated accounts

This page was my guide: https://gist.github.com/oanhnn/80a89405ab9023894df7

This page provided a refresher: Adding a new SSH key to your GitHub account

And this page: Adding a new SSH key to your GitHub account

This page helped with the git command-line stuff: https://www.atlassian.com/git/tutorials/git-forks-and-upstreams

Local Setup

My primary SSH key was already generated and store in my .ssh directory.

I generated a new SSH key to associate with the Delligatti Associates account:

$ ssh-keygen -t rsa -b 4096 -C "jthompson@delligattiassociates.com"

Part of generating the key is specify where it will be stored. I specified the name da_private_key and two files are generated:

da_private_key
da_private_key.pub

This isn't necessary for using git, but will add the new key to my macOS keychain:

$ ssh-add da_private_key

On Github.com

I followed this procedure for adding the new key to the Delligatti Associates Github account: Adding a new SSH key to your GitHub account

Github noted the new SSH key...

Error creating thumbnail: File missing

...and sent an email to jthompson@delligattiassociates.com, which was the name associated with the key:

Error creating thumbnail: File missing

Finishing local setup

Next I edited ~/.ssh/config to add clauses for both the default github accound and the DA account. Note the difference between the Host and the Hostname definitions:

# Default github account: jimthompson
Host github.com
   HostName github.com
   IdentityFile ~/.ssh/id_rsa
   IdentitiesOnly yes
   
# Other github account: da (delligattiassociates)
Host github-da
   HostName github.com
   IdentityFile ~/.ssh/da_private_key
   IdentitiesOnly yes

I tested access to github-da:

$ ssh -T git@github-da

And I tested access to github.com to make sure it hadn't broken:

$ ssh -T git@github.com

Testing a push

On the Github page for the Remailer repository, https://github.com/delligattiassociates/remailer, I copied the git ID for access to the repository, which is git@github.com:delligattiassociates/remailer.git. To ensure that the correct key is used, the hostname github.com is changed to the host alias defined in the SSH config: da-github, producing:

git@github-da:delligattiassociates/remailer.git

I added this as a new remote for my local copy of the remailer repository:

$ git remote add da git@github-da:delligattiassociates/remailer.git

I verified that the new remote was added for the local repository:

$ git remote -v
da	git@github-da:delligattiassociates/remailer.git (fetch)
da	git@github-da:delligattiassociates/remailer.git (push)
origin	git@github.com:jim-thompson/remailer.git (fetch)
origin	git@github.com:jim-thompson/remailer.git (push)

Finally, I tested by pushing recent changes to the Delligatti Associates Github remailer repository:

$ git push da
Enumerating objects: 26, done.
Counting objects: 100% (26/26), done.
Delta compression using up to 20 threads
Compressing objects: 100% (22/22), done.
Writing objects: 100% (22/22), 7.34 KiB | 7.34 MiB/s, done.
Total 22 (delta 14), reused 0 (delta 0), pack-reused 0
remote: Resolving deltas: 100% (14/14), completed with 3 local objects.
To github-da:delligattiassociates/remailer.git
   c771e4c..0d0550f  main -> main

Note

To make da the default upstream:

$ git push --set-upstream da main

Now commands like git status or git push will use da as the default upstream:

$ git status
On branch main
Your branch is up to date with 'da/main'.

nothing to commit, working tree clean

Here's how to clone the remailer (it's a private remailer, so the authentication matters even in the clone):

$ git clone git@github-da:delligattiassociates/remailer.git