Managing Multiple GitHub Accounts on a Single Machine#

1. Generate SSH Keys for Each Account#

First, create separate SSH keys for each GitHub account:

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# Navigate to SSH directory
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cd ~/.ssh
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# Generate SSH key for work account
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ssh-keygen -t rsa -b 4096 -C "work@email.com" -f "github-work"
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# Generate SSH key for personal account
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ssh-keygen -t rsa -b 4096 -C "personal@email.com" -f "github-personal"

Use strong, unique passphrases for each key for added security.

2. Add SSH Keys to the SSH Agent#

Add your newly created SSH keys to the SSH agent:

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# Start SSH agent if it's not running
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eval "$(ssh-agent -s)"
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# Add work SSH key
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ssh-add ~/.ssh/github-work
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# Add personal SSH key
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ssh-add ~/.ssh/github-personal

On macOS, you might want to use ssh-add -K to store the passphrase in your keychain.

3. Add Public Keys to GitHub Accounts#

You need to add each public key to its respective GitHub account:

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# Copy the work public key to clipboard (macOS)
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pbcopy < ~/.ssh/github-work.pub
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# For Linux, you can use:
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# cat ~/.ssh/github-work.pub

Then:

1. Log in to your work GitHub account
2. Go to Settings → SSH and GPG keys → New SSH key
3. Paste the key content, give it a descriptive title (e.g., “Work Laptop”), and save
4. Repeat the process for your personal account using the github-personal.pub key

4. Create an SSH Config File#

Create or edit the SSH config file to set up custom hosts:

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# Edit SSH config file
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nano ~/.ssh/config

Add the following configuration:

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# Work GitHub account
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Host github.com-work
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    HostName github.com
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    User git
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    IdentityFile ~/.ssh/github-work
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    IdentitiesOnly yes
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# Personal GitHub account
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Host github.com-personal
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    HostName github.com
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    User git
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    IdentityFile ~/.ssh/github-personal
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    IdentitiesOnly yes

The IdentitiesOnly yes setting is crucial as it forces SSH to use only the specified identity file, preventing key confusion.

5. Testing Your Configuration#

Verify that both configurations work correctly:

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# Test work configuration
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ssh -T git@github.com-work
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# Test personal configuration
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ssh -T git@github.com-personal

You should see a message like: “Hi username! You’ve successfully authenticated, but GitHub does not provide shell access.” for each account, with the respective username.

Cloning New Repositories#

When cloning repositories, use the appropriate custom host:

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# Clone work repository
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git clone git@github.com-work:work-organization/repository.git
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# Clone personal repository
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git clone git@github.com-personal:personal-username/repository.git

Updating Existing Repositories#

If you already have repositories cloned, update the remote URL:

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# For work repositories
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git remote set-url origin git@github.com-work:work-organization/repository.git
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# For personal repositories
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git remote set-url origin git@github.com-personal:personal-username/repository.git

Setting User Configuration#

Set the correct user configuration for each repository:

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# Navigate to your repository
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cd /path/to/repository
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# For work repositories
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git config user.email "work@email.com"
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git config user.name "Your Work Name"
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# For personal repositories
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git config user.email "personal@email.com"
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git config user.name "Your Personal Name"

This ensures your commits are properly attributed to the right account.

Directory-Based Configuration#

For a more automatic setup, you can use conditional includes in your global .gitconfig based on the directory path:

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# Edit global Git config
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nano ~/.gitconfig

Add the following:

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[includeIf "gitdir:~/work/"]
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    path = ~/.gitconfig-work
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[includeIf "gitdir:~/personal/"]
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    path = ~/.gitconfig-personal

Then create the specific configuration files:

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# Work Git config
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nano ~/.gitconfig-work

With content:

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[user]
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    email = work@email.com
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    name = Your Work Name
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[core]
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    sshCommand = ssh -i ~/.ssh/github-work -F /dev/null

And personal config:

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# Personal Git config
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nano ~/.gitconfig-personal

With content:

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[user]
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    email = personal@email.com
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    name = Your Personal Name
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[core]
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    sshCommand = ssh -i ~/.ssh/github-personal -F /dev/null

With this setup, Git automatically uses the correct identity based on the directory path of your repository.

Using Multiple Remote URLs#

An alternative approach is to use multiple remote URLs for the same repository:

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# Add multiple remotes to a repository
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git remote add work git@github.com-work:work-organization/repository.git
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git remote add personal git@github.com-personal:personal-username/repository.git
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# Push to specific remote
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git push work main
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git push personal main

This method is useful for repositories that you manage under both accounts.

Permission Denied Error#

If you get a “Permission denied (publickey)” error:

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# Check if SSH agent has the key
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ssh-add -l
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# If your key isn't listed, add it
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ssh-add ~/.ssh/github-work

Also verify that you’ve added the correct public key to the GitHub account.

Wrong Account Being Used#

If commits are being attributed to the wrong account:

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# Check the repository's Git config
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git config --list
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# Verify the remote URL
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git remote -v

Ensure that your repository’s configuration and remote URL match the account you want to use.

SSH Agent Issues#

If the SSH agent isn’t remembering your keys between sessions:

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# For macOS, add this to your .bash_profile or .zshrc
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ssh-add -A
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# For other systems, consider using ssh-agent with your desktop environment
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# or add this to your .bashrc or .zshrc:
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if [ -z "$SSH_AUTH_SOCK" ] ; then
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    eval "$(ssh-agent -s)"
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    ssh-add ~/.ssh/github-work
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    ssh-add ~/.ssh/github-personal
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fi

Handling Git Credential Helper#

If you’re still using HTTPS for some repositories and having credential issues:

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# Clear cached credentials
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git credential reject
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protocol=https
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host=github.com
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# Or disable credential helper for a repository
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git config --local credential.helper ""