Using multiple SSH keys with GitHub

I have a couple of different accounts for GitHub¹ - one for my personal projects, and one for work. GitHub doesn’t allow the same SSH key to be used on different accounts which can make working with repositories difficult.

For example, cloning a private repository from one account may not work, even if both keys are currently being used by the SSH agent.

To workaround this limitation, the SSH agent can be configured to use a specific key when accessing a domain. In this case the same domain requires different keys, so an alias is used instead.

This alias needs to be used when checking out repositories, but once the initial step is complete everything else happens automatically.

Modifying ~/.ssh/config with the following:

# Work GitHub Account
Host github.com-work
    HostName github.com
    User git
    IdentityFile ~/.ssh/work_public_key

Will now tell the SSH agent to use ~/.ssh/work_public_key when trying to access anything on github.com-work.

Cloning a repository

To use the alias when cloning a reposiory, replace github.com with the configured alias.

For example, cloning the ruby repository with the work alias from earlier looks like this:

git clone git@github.com-work:ruby/ruby.git

Standard git commands like git push will work just the same as any other repository.

Existing repositories

To update an existing repository to use a new alias, modify the .git/config file in the project’s working directory. It should look something like this:

[remote "origin"]
	url = git@github.com-work:ruby/ruby.git