GitHub Error: Key already in use

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:

git@github.com:<gh_username>/<gh_reponame>.git

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 git@github.com

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

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 git@github.com/<reponame>.git

You probably just need to change the name of your key.

ssh-keygen -t rsa -b 4096 -C "<email>"

Then it will ask to enter the file name, make sure that you enter the path name which does not exist on your system. Usually, "id_rsa" file name is created by default on MAC. Just change the name and then use following command to copy

pbcopy < {Path where SSH-Keygen is stored}

That's it. You can simply paste this keygen (copied from above command on the clipboard) in GitHub and use that without any problem.

This works for me,

Generate the SSH keys using ssh-keygen. Let's say the key is in ~/.ssh/id_rsa_foo Now, $ cat ~/.ssh/id_rsa_foo.pub and paste it on your GitHub keys. You can use GIT_SSH_COMMAND environment variable to achieve what you want. Do $ GIT_SSH_COMMAND='ssh -i ~/.ssh/id_rsa_foo' git push origin master. Check your Github repo for the magic. Cheers!

you can use the same ssh key for different github repositories but cannot use the same ssh key for many repositories (i.e,same repository from different logins or from forked) as github will not allow same deploy key more than once for a repository

You can create a different key in your machine without disturbing your existing keys like:ssh-keygen -t rsa -C "your_email@example.com"
Now provide your file name to identify your key for the repository

Enter file in which to save the key (/home/demo/.ssh/id_rsa):/home/demo/.ssh/id_rsa_mykey<br>

See https://developer.github.com/guides/managing-deploy-keys/#deploy-keys for details.

I've found a workaround that works for me:

You cannot add the same SSH key to different accounts, and that is true for GitHub, BitBucket, etc. But you can use different SSH keys for each account. The only downside then is how to easily switch between them?

I use ssh-agent and it can use multiple keys at the same time. I auto add them through .bashrc

if [ -z "$SSH_AUTH_SOCK" ] ; then
  eval `ssh-agent -s`
  ssh-add ~/.ssh/id_rsa
  ssh-add ~/.ssh/id_rsa2
fi

This approach works regardless of which key is added in your GitHub account. I guess ssh-agent makes attempts with each key until it succeeds. And if you don't want to add all keys, you just comment out the relevant line in the .bashrc before starting a new shell.