SSH Client setup using keys

Bradley Stannard -

The following steps will setup your ssh keypairs on your local machine, copy the public key to your server, and configure your ssh client to use a specific private key with a server alias.

First, generate your keypair, I generally name the keys with my username-service, username-hostname, or username-device, sometimes even a combination of the three.


To generate keys for a new server at securedomain.com


ssh-keygen -t rsa -b 4096 -C 'email@securedomain.com'

Things to keep in mind:

  • The email does not have to be the same domain as the service/server you are connecting to
  • The -t rsa -b 4096 options are safe and will work on most servers, you can also use -t ed25519 if you wish.

Once you're in the ssh-keygen prompt it will ask you to provide a name for your keys

NOTE: You can also do this in the command itself using the -f <filename>


Generating public/private rsa key pair. Enter file in which to save the key (/home/user/.ssh/id_rsa):<new_key_name>

The ssh-keygen application will then, prompt you for a passphrase to secure your key. (You don't have to, but it is recommended). If you don't wish to use a passphrase just press enter twice.

Now, we need to copy our keys to the server, we do so by entering the following


ssh-copy-id -i .ssh/yourkeyfile username@hostname

This will effectively copy your keyfile over to the new server in a secure fashion. More reading on this here.

Next, you will want to add the key to your ~/.ssh/config to be used automatically with the specified host it was created for; this saves the leg work of having to remember which key goes with which host, and also from having to type -i /path/to/key options with your ssh command.


To do this, first we need to edit our config, so open up ~/.ssh/config in your preferred editor and enter the following:

# EXAMPLE
# This will setup the use of example as an alias for the FQDN of the server you want to connect to

Host example
    Hostname example.securedomain.com
    AddKeysToAgent yes
    UseKeychain yes
    IdentityFile ~/.ssh/securedomain_username

In this config the following are true:

  • Host is an alias to the server we wish to connect to, it does not have to match the domain name.
  • Hostname is the actual FQDN of the server we wish to connect to
  • AddKeysToAgent tells ssh to add the specified keyfiles to our existing ssh-agent
  • UseKeychain tells ssh to utilize the keychain, which either starts the ssh-agent, or connects to an already running instance saving the trouble of typing the passphrase for a given key if you're logging in and out of a server frequently.
  • IdentityFile is your keyfile you wish to use for the host you are configuring; probably the key you just generated.

Using this config and example; we can now use the following command


ssh user@example

Which using this config, in the background is expanded out to the following command


ssh -i ~/.ssh/securedomain_username user@example.securedomain.com

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