GitHub Error: Key already in use

Question

I have created two GitHub accounts. One for my work user and one for my personal self. I needed to do catch up on some work and as such cloned my work repo onto my personal PC. In order to do simple "git push origin master" commits without entering my username and password the whole time I simply want to add my public key from my home pc to the work repo. However Github gives this error:

Error: Key already use

After a bit of Googling I came across this link which states "To resolve the issue, remove the key from the other account or repository and add it to your account" Of course there is a duplicate key as I've added my home public key to github so that I can code on my own personal projects. After all I want to be able to code to my work repo using both my work pc and personal pc.

How can you add multiple "same" public keys without Github throwing that error and also why in the world, is that error thrown in the first place?

Answer 1

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/id_rsa git@github.com

to find the used key, delete it and then readd it again in the right user/repo. that was very useful for me

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

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edit: as pointed out by @mikhail-morgunov, this doesn't works all the time, you should really use this snippet only if the default id_rsa SSH private key is your github's default one

this is a snippet where the key name has been extracted:

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

Answer 2

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

Answer 3

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

Answer 4

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.