Managing multiple GitHub accounts on macOS

If you want to use multiple GitHub accounts with SSH keys on your computer, you have to adapt your ssh- and git-configuration.

In this tutorial I’ll explain the configuration steps for the following scenario:

GitHub user 1

• username: user01
• name: John Doe
• email: john.doe@abc.com
• repository: git@github.com:user01/testrepo01.git

GitHub user 2

• username: user02
• name: John Doe
• email: jd@work.com
• repository: git@github.com:user02/testrepo02.git

1. Create SSH keys for your accounts

$ ssh-keygen -t rsa -b 4096 -C "id_rsa_github_user01" -f ~/.ssh/id_rsa_github_user01
$ ssh-keygen -t rsa -b 4096 -C "id_rsa_github_user02" -f ~/.ssh/id_rsa_github_user02

When you create your ssh keys you can decide, wether you encrypt your private keys with a passphrase or not.

TIP: The purpose of the passphrase is to encrypt your private key. This makes the key file by itself useless to any attackers.

Now you should have the following files:

• ~/.ssh/id_rsa_github_user01
• ~/.ssh/id_rsa_github_user01.pub
• ~/.ssh/id_rsa_github_user02
• ~/.ssh/id_rsa_github_user02.pub

2. Add your SSH keys to the agent

To automatically load the keys into the ssh-agent and to store your passphrases in the keychain, add the following code to your ~/.ssh/config.

# global
Host *
 UseKeychain yes
 AddKeysToAgent yes

Now you have to add your keys to the ssh agent. With the option -K you store your passphrases in the keychain.

$ ssh-add -K ~/.ssh/id_rsa_github_user01
# here you have to enter your passphrases
$ ssh-add -K ~/.ssh/id_rsa_github_user02
# here you have to enter your passphrases

Check if the keys are successfully added.

$ ssh-add -l
4096 SHA256:O2MoTWlJD8yE+VxrxR5bOu0 ~/.ssh/id_rsa_github_user01 (RSA)
4096 SHA256:W2cnWtNK9tU9/dkWvOjLxNQ ~/.ssh/id_rsa_github_user02 (RSA)

3. Add your public ssh key to the GitHub

Add your public ssh key to the GitHub user 1

Copy your public key to your clipboard.

$ pbcopy < ~/.ssh/id_rsa_github_user01.pub

Login to your GitHub account user01. Go to https://github.com/settings/ssh/new, type in a title (e.g. id_rsa_github_user01), paste your key and click ‘Add SSH key’. Now you have to confirm with your GitHub password.

Add your public SSH key to the GitHub user 2

Copy your public key to your clipboard.

$ pbcopy < ~/.ssh/id_rsa_github_user02.pub

Login to your GitHub account user02. Go to https://github.com/settings/ssh/new, type in a title (e.g. id_rsa_github_user02), paste your key and click ‘Add SSH key’. Now you have to confirm with your GitHub password.

4. Preconfigure git

To prevent you from committing to a GitHub repository with a wrong committer email address or username, you should remove the email address and name from the global git config. These 2 configs, Email address and username, should be configured for each repository separately.

# Remove email address from global config:
$ git config --global --unset-all user.email
$ git config --global --unset-all user.name

# Require setting user.name and email per-repo:
$ git config --global user.useConfigOnly true

5. Add SSH keys to you git config

#GitHub account user01
Host id_rsa_github_user01
  HostName github.com
  User user01
  PreferredAuthentications publickey
  IdentityFile ~/.ssh/id_rsa_github_user01

#GitHub account user02
Host id_rsa_github_user02
  HostName github.com
  User user02
  PreferredAuthentications publickey
  IdentityFile ~/.ssh/github.com-work

6. Clone a GitHub repository

Every time you want to clone a repository from github, you have to replace github.com in the clone url with the corresponding host-id from your ~/ssh/config.

Example:

# user01 wants to clone git@github.com:user01/testrepo01.git
$ git clone git@id_rsa_github_user01:user01/testrepo01.git

After a successful clone you have to configure the user.name and user.email of the repository.

$ git config user.name "John Doe"
$ git config user.email "john.doe@abc.com"