Managing multiple GitHub accounts on the same computer can be challenging, but it’s essential for developers working with different clients or projects. This comprehensive guide shows you how to set up and manage multiple GitHub accounts using SSH keys on macOS, with practical examples and best practices.

Prerequisites

Before you begin, ensure you have:

  • macOS (this guide is for macOS, but YMMV on other operating systems)
  • Git installed
  • SSH installed
  • Access to your GitHub accounts
  • Terminal access
  • Basic understanding of SSH and Git concepts

Setting Up Multiple GitHub Accounts

1. Generate SSH Keys

Use the following shell function to generate and configure SSH keys for each GitHub account:

ssh_key_gen() {
    if [ $# == 0 ]; then
        echo "Usage: ${FUNCNAME} [EMAIL] [KEY_NAME]"
        echo "1. Generate a key"
        echo "2. Copy the public key to the clipboard"
        return
    fi

    email="$1"
    key_name="$2"
    rsa_key_name="id_rsa_${key_name}"
    rsa_key_path="${HOME}/.ssh/${rsa_key_name}"

    ssh-keygen \
        -t rsa \
        -C "${email}" \
        -f "${rsa_key_path}"

    cat "${rsa_key_path}.pub" | pbcopy
    ssh-add "${rsa_key_path}"

    ssh_config_entry=$(cat <<-END
Host github.com
  HostName github.com
  User git
  IdentityFile "${rsa_key_path}"
END
    )
    ssh_config_path="${HOME}/.ssh/config"
    if ! grep "${ssh_key_name}" "${ssh_config_path}"; then
        echo "Key already exists in ${ssh_config_path}"
    else
        echo "${ssh_config_entry}" >> "${ssh_config_path}"
    fi
}

2. Configure Your GitHub Account

  1. Run the function with your email and key name:
ssh_key_gen your.email@domain.com your_key_name
  1. Enter your passphrase when prompted
  2. Add a new SSH key to your GitHub account
  3. Test your configuration by cloning a repository

3. Verify Configuration

# Test SSH connection
ssh -T git@github.com

# Check loaded keys
ssh-add -L

# Verify SSH config
cat ~/.ssh/config

Managing Multiple SSH Keys

Switching Between Accounts

To switch between different GitHub accounts, use these commands:

# Remove all loaded SSH keys
ssh-add -D

# Load your primary key
ssh-add ~/.ssh/id_rsa

# When done, remove the primary key
ssh-add -D

# Load your secondary key
ssh-add ~/.ssh/your_key_name

Managing SSH Keys

Use these utility functions to manage your SSH keys:

# Delete an SSH key
ssh_key_delete() {
    if [ $# == 0 ]; then
        echo "Usage: ${FUNCNAME} [KEY_NAME]"
        echo "1. Delete a key"
        return
    fi

    key_name="$1"
    rsa_key_name="id_rsa_${key_name}"
    rsa_key_path="${HOME}/.ssh/${rsa_key_name}"

    ssh-add -D "${rsa_key_name}" \
    && rm -f "${rsa_key_path}"* \
    || echo "Delete failed: ${rsa_key_path}"
}

# List all loaded SSH keys
ssh_key_list() {
    ssh-add -L
}

Git Configuration

Per-Repository Settings

For repositories that need specific user information:

# Set local Git configuration
git config user.name "Your Name"
git config user.email "your.email@domain.com"

# Verify settings
git config --local -l

Global Settings

For default Git configuration:

# Set global Git configuration
git config --global user.name "Your Name"
git config --global user.email "your.email@domain.com"

# Verify settings
git config --global -l

Security Best Practices

  1. SSH Key Management

    • Use descriptive names for your SSH keys
    • Keep your private keys secure
    • Use strong passphrases
    • Regularly rotate your SSH keys
    • Never share private keys

  2. Access Control

    • Use different SSH keys for different accounts
    • Implement key expiration policies
    • Monitor key usage
    • Revoke compromised keys immediately

  3. Repository Security

    • Use repository-specific Git configurations
    • Implement branch protection rules
    • Enable two-factor authentication
    • Regular security audits

Troubleshooting

Common Issues

  1. SSH Connection Problems

    • Verify SSH configuration file (~/.ssh/config)
    • Check if SSH keys are loaded (ssh-add -L)
    • Test SSH connection (ssh -T git@github.com)
    • Ensure GitHub account has correct SSH key

  2. Git Configuration Issues

    • Check local and global Git settings
    • Verify repository-specific settings
    • Ensure correct user information
    • Check Git credentials

  3. Permission Issues

    • Verify SSH key permissions
    • Check repository access rights
    • Ensure correct account association
    • Validate SSH agent status

Automation and Scripts

Key Management Script

Create a script to automate key management:

#!/bin/bash

# Load all keys for a specific account
load_github_keys() {
    local account=$1
    ssh-add -D
    ssh-add ~/.ssh/id_rsa_${account}
}

# Switch between accounts
switch_github_account() {
    local account=$1
    load_github_keys ${account}
    git config --global user.email "your.${account}@domain.com"
}

Further Reading