macOS SSH Key Auto-Configuration for Git

Prerequisites: Generate SSH Key Pair

1. Open Terminal
   Use Spotlight (⌘+Space) to search for “Terminal” and open it.

2. Generate Key Pair
   Execute the following command (replace [email protected] with your email):

   ssh-keygen -t ed25519 -C "[email protected]" -f ~/.ssh/git_example

   • When prompted, press Enter to use default settings.
   • For extra security, you can set a passphrase.

3. Check Generated Files
   Two files will be created in the ~/.ssh directory:

   git_example    # Private key (keep secure)
   git_example.pub # Public key (to be configured on Git server)

Configure Automatic Use of Specified Key

1. Edit SSH Config File

   mkdir -p ~/.ssh && chmod 700 ~/.ssh
   vim ~/.ssh/config

2. Add Configuration
   Use the following template (modify parameters as needed):

   # Main Git service configuration
   Host git.example.com
       HostName git.example.com
       User git
       Port 22
       IdentityFile ~/.ssh/git_example
       IdentitiesOnly yes
   
   # Additional configuration (for other Git services)
   Host github.com
       HostName github.com
       User git
       IdentityFile ~/.ssh/github_key

3. Set File Permissions

   chmod 600 ~/.ssh/config

Server-Side Configuration

1. Add Public Key to Git Service
   Copy the public key content:

   pbcopy < ~/.ssh/git_example.pub

   Add the public key to:
   • GitHub: Settings → SSH and GPG keys
   • GitLab: Preferences → SSH Keys
   • Self-hosted Git service: Server’s ~/.ssh/authorized_keys file

Verify Configuration

1. Test SSH Connection

   ssh -T [email protected]

   On success, you will see a welcome message from the service (e.g., GitHub’s “Hi username!”).

2. Test with Repository Clone

   git clone [email protected]:username/repo.git

   The system will automatically use the specified key without manual intervention.

Troubleshooting

1. Debug Mode
   Add the -v flag to see detailed connection process:

   ssh -Tv [email protected]

2. Common Issues

   • Error Permissions 0644 are too open: Run chmod 600 ~/.ssh/*
   • Connection timeout: Check firewall settings or network proxy configuration.
   • Authentication failed: Confirm that the public key has been correctly added to the server.

Extended Use

By configuring multiple Host blocks, you can:

• Use different keys for different platforms (GitHub/GitLab/Gitee)
• Separate work and personal accounts
• Manage keys in multi-server environments

Note: The git.example.com in this article is a placeholder. Replace it with your actual Git service address.