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How to Generate and Store SSH Keys

in ssh · 3 min read

How to Generate and Store SSH Keys

There are two methods of logging into a remote system with SSH - using a password based login or by using SSH keys. Both have their pros and cons, but this article is going to focus on generating SSH keys and storing them in a config file for easy logins. This article will focus on the creation of new SSH keys.

Example

Always create a new name for the key pair when generating keys. For example, identify the key as id_rsa_mac for Macbook Pro, or id_rsa_local. These are two examples, but they can be named anything.

Generating SSH Keys

Follow these instructions to create SSH keys.

  • Create a new key pair
    • Open a terminal and run the following command: ssh-keygen
    • You will be prompted to save and name the key.
    • Generating public/private rsa key pair. Enter file in which to save the key (/Users/USER/.ssh/id_rsa):
    • Next you will be asked to create and confirm a passphrase for the key (highly recommended): Enter passphrase (empty for no passphrase): Enter same passphrase again:
    • This will generate two files, by default called id_rsa and id_rsa.pub.
    • Next, add this public key to each applicable machine.

Two files were created:

  1. id_rsa_xxx – this is your key file that sits on the local machine.
  2. id_rsa_xxx.pub – this is the public file that goes to your remote server.

Copy the Public Key to a Remote Server

In order to copy the public key to the remote server, there are two different syntaxes that can be used:

ssh-copy-id [email protected]

ssh-copy-id -i id_rsa_xxx.pub [email protected]

This first is most effective when there is only one SSH key on a machine to copy, whereas the second should be used when there are multiple keys located on the local machine.

Managing Multiple Keys

It’s good to have many keys, but by default, the id_rsa.pub file is always used unless noted otherwise. It will be required to tell ssh to look for a different public key file depending on the service. This is where the config files come in.

Config file

The config file is located at ~/.ssh/config. if it’s not there, it will need to be created manually as follows:

sudo nano ~/.ssh/config

The contents of the file will need to look like the following:

Host           server1
HostName       192.0.2.10
Port           22
IdentityFile   ~/.ssh/id_rsa_xxx
User           admin
  • Host - this can be anything, but will generally be the name of the server.
  • HostName - IP or host name. For our needs, use the IP address.
  • Port - the port on the server that SSH is mapped to.
  • IdentityFile - where the key file is located.
  • User - the user we will be logging in as.

Now, in order to log into a particular server, the following syntax would be used:

$ ssh myserver.

Add more servers as needed.

Host           server1
HostName       192.0.2.10
Port           22
IdentityFile   ~/.ssh/id_rsa_xyz
User           admin

Host           server2
HostName       192.0.2.11
Port           22
IdentityFile   ~/.ssh/id_rsa_xyz
User           admin

References

https://www.digitalocean.com/docs/droplets/how-to/add-ssh-keys/create-with-openssh/

https://clubmate.fi/how-to-setup-and-manage-multiple-ssh-keys/

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