Let’s suppose you need to use a different SSH key-pair per Git repository e.g. Github’s deploy key that is stored on the server and grants access to a single repository. Using named servers you can easily automate the process of managing multiple keys.
We will be using a single server to store all SSH keys, i.e. anyone with access to this server has access to a particular repository. Let’s call it « Github Proxy ».
Start by generating a new key pair. I use application name followed by server name to easily identify a particular key.
ssh-keygen -t rsa -C “acme@boo”
When asked about the key name, use the application name
Generating public/private rsa key pair. Enter file in which to save the key (/Users/you/.ssh/id_rsa): acme
Adjust .ssh/config and define your named server
Host acme Hostname github.com User git IdentityFile ~/.ssh/acme
Next, assign your public key, in our case acme.pub, to your Github repository.
Let’s assume our organisation name on Github is acmecorp and our application is acmecorp/acme. Go to Settings -> Deploy Keys, click Add deploy key and paste the content of acme.pub there.
Finally, log in to your Github Proxy server and check if you can clone the repository. Notice we are using our defined name with git clone.
git clone acme:acmecorp/acme.git
With such setup we introduced a level of indirection: users of Github Proxy don't have to change anything in their local settings - as long as they have access to that server, they can access code repositories on Github.
Quite nifty!