GitHub Error: Key already in use

The key could be already in use on other github projects as deploy key, that's a bit tricky to find but run:

ssh -T -ai ~/.ssh/KEY_NAME [email protected]

change KEY_NAME with the name of your SSH private key and you will be good to go

from: https://help.github.com/articles/error-key-already-in-use/#finding-where-the-key-has-been-used

You can create one more key pair, say id_rsa_personal.pub, and add it to the Github account.

Next, create/edit the .ssh/config file.

# Default GitHub
Host github.com
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_rsa

Host github-public
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_rsa_public

Host github-personal
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_rsa_personal

The above file will help you to use more than one Github account. For background info, refer to the answers to this question.

Next, you will need to alter your .git/config remote url to point to:

git@github-personal:<gh_username>/<gh_reponame>.git

Rather than the usual:

[email protected]:<gh_username>/<gh_reponame>.git

John commented that it didn't work for him.

Perhaps the step you're missing is you need to alter your .git/config remote url to point to git@github-personal/<reponame>.git etc.. rather than the usual [email protected]/<reponame>.git