How can multiple private keys be used with ssh?

Question

I was able to setup ssh to use private/public key authentication. Now I am able to do

ssh user@server1

And it logs on with the private key. Now I want to connect to another server and use a different key. How do set it up so

ssh user@server1

uses privatekey1

ssh user@server2

and uses privatekey2

Answer 1

You can set this up in your ~/.ssh/config file. You would have something like this:

Host server1
IdentityFile ~/.ssh/key_file1

Host server2
IdentityFile ~/.ssh/key_file2

man ssh_config is a reference

Answer 2

There are a few options.

1. Load both keys into your ssh agent using ssh-add. Then both keys will be available when connecting to both servers

2. Create your $HOME/.ssh/config file and create a Host section for server1 and another for server2. In each Host section, add an IdentityFile option pointing to the appropriate private key file

Answer 3

Besides the (preferable) option of adding both keys in $HOME/.ssh/config (note that this requires appropriately setting attributes of $HOME/.ssh and $HOME/.ssh/config), you can use

$ ssh -i privatekey1 user@server1

e.g.

I learned this by way of solving this more complex situation: Multiple ssh access types from a given user1/client to the same user2/server