Manage multiple SSH keys and Git accounts

multiple_ssh_keys.md

Managing multiple SSH keys and Git accounts

It can sometimes be useful to have multiple SSH keys for the same Git hosts, which requires some additional SSH configuration.

Example

A typical example involves using the same host (GitHub) with multiple accounts on the same computer. Since each account should use its own SSH key, we need to use a combination of the SSH configuration and Git remotes to determine which SSH key to use.

Configuration

1. Generate a unique SSH key for each use case

SSH keys should follow the following naming format: [Host]-[Use] (ie. github-personal).

• Host - Host the key will be associated with
  • ie. github for GitHub repositories
• Use - What kind of work the key will be used for
  • ie. personal for personal work

~/.ssh/
  id_rsa.github-personal
  id_rsa.github-personal.pub

Keys can be generated using the following command: ssh-keygen -t rsa -C "[EMAIL_ADDRESS]" -b 4096

Add the key to the ssh agent:

eval $(ssh-agent -s)
ssh-add ~/.ssh/other_id_rsa

2. Modify your SSH config file (typically ~/.ssh/config) with the required hosts and identity files

The SSH config file is typically located at ~/.ssh/config.

• Host - Host name for referencing later (in Git config)
• HostName - Actual host name
• User - User who will be using the credentials
• IdentityFile - SSH private key file
• IdentitiesOnly - Prevents falling back to the default key

# ~/.ssh/config

Host github-personal
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_rsa.github-personal
  IdentitiesOnly yes

Host github-work
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_rsa.github-work
  IdentitiesOnly yes

3. Modify the Git remote urls

The new SSh configuration will be used when attempting to connect to a Git remote, meaning that if the Git remote URL is updated to match the configuration's Host parameter it will use the nested information.

remote["origin"]
  git@github-personal:username/repository.git

4. Add the SSH Key to Remote

SSH keys should follow the following naming format when added to the remote: [Host]-[Use]-[Location] (ie. github-personal-macbook).

• Host - Host the key will be associated with
  • ie. github for GitHub repositories
• Use - What kind of work the key will be used for
  • ie. personal for personal work
• Location - Physical location of the key (one place only)
  • ie. macbook for key created on a MacBook