Best way to use multiple SSH private keys on one client [closed]

From my .ssh/config:

Host myshortname realname.example.com
    HostName realname.example.com
    IdentityFile ~/.ssh/realname_rsa # private key for realname
    User remoteusername

Host myother realname2.example.org
    HostName realname2.example.org
    IdentityFile ~/.ssh/realname2_rsa  # different private key for realname2
    User remoteusername

Then you can use the following to connect:

ssh myshortname

ssh myother

And so on.

You can instruct ssh to try multiple keys in succession when connecting. Here's how:

$ cat ~/.ssh/config
IdentityFile ~/.ssh/id_rsa
IdentityFile ~/.ssh/id_rsa_old
IdentityFile ~/.ssh/id_ed25519
# ... and so on

$ ssh server.example.com -v
....
debug1: Next authentication method: publickey
debug1: Trying private key: /home/example/.ssh/id_rsa
debug1: read PEM private key done: type RSA
debug1: Authentications that can continue: publickey
debug1: Trying private key: /home/example/.ssh/id_rsa_old
debug1: read PEM private key done: type RSA
....
[server ~]$

This way you don't have to specify what key works with which server. It'll just use the first working key.

Also you would only enter a passphrase if a given server is willing to accept the key. As seen above ssh didn't try to ask for a password for .ssh/id_rsa even if it had one.

Surely it doesn't outbeat a per-server configuration as in other answers, but at least you won't have to add a configuration for all and every server you connect to!

The answer from Randal Schwartz almost helped me all the way. I have a different username on the server, so I had to add the User keyword to my file:

Host           friendly-name
HostName       long.and.cumbersome.server.name
IdentityFile   ~/.ssh/private_ssh_file
User           username-on-remote-machine

Now you can connect using the friendly-name:

ssh friendly-name

More keywords can be found on the OpenSSH man page. NOTE: Some of the keywords listed might already be present in your /etc/ssh/ssh_config file.

The previous answers have properly explained the way to create a configuration file to manage multiple ssh keys. I think, the important thing that also needs to be explained is the replacement of a host name with an alias name while cloning the repository.

Suppose, your company's GitHub account's username is abc1234. And suppose your personal GitHub account's username is jack1234

And, suppose you have created two RSA keys, namely id_rsa_company and id_rsa_personal. So, your configuration file will look like below:

# Company account
Host company
HostName github.com
PreferredAuthentications publickey
IdentityFile ~/.ssh/id_rsa_company

# Personal account
Host personal
HostName github.com
PreferredAuthentications publickey
IdentityFile ~/.ssh/id_rsa_personal

Now, when you are cloning the repository (named demo) from the company's GitHub account, the repository URL will be something like:

Repo URL: [email protected]:abc1234/demo.git

Now, while doing git clone, you should modify the above repository URL as:

git@company:abc1234/demo.git

Notice how github.com is now replaced with the alias "company" as we have defined in the configuration file.

Similary, you have to modify the clone URL of the repository in the personal account depending upon the alias provided in the configuration file.

ssh-add ~/.ssh/xxx_id_rsa

Make sure you test it before adding with:

ssh -i ~/.ssh/xxx_id_rsa [email protected]

If you have any problems with errors sometimes changing the security of the file helps:

chmod 0600 ~/.ssh/xxx_id_rsa