How-To Add Additional SSH Keys to Instances

Last Updated: November 26, 2025

Introduction

The following article will explain how to add additional public SSH keys to your Crusoe Cloud instances. 

At the moment, the Crusoe Cloud UI doesn't offer a feature to upload an SSH key and automatically apply it across all VMs. You're only able to apply one public SSH key during the creation of an instance.

Prerequisite 

• Crusoe Cloud account

Instructions

To grant your colleague access (or to add additional public SSH keys) to your instances, you'll need to individually SSH into each instance and manually add their public key as a new line in the ~/.ssh/authorized_keys file.

(The ~/.ssh/authorized_keys file path is standard in all Linux-based systems.)

Step 1:

• SSH to your instance:

  ssh ubuntu@<public_IP_address>

Step 2:

• Use a text editor of your choice such as nano or vi to modify the file:

  nano ~/.ssh/authorized_keys

Step 3:

• Simply paste any additional public SSH keys as a new line below your existing key.
  Here's an example of how the ~/.ssh/authorized_keys file should look: 

  ssh-ed25519 AAAAC3NzaC2SAJDFHKJFjhFjhJHFHsdfasdf6+ test_user_1@my_machine.local
  ssh-ed25519 AAAAC5DasdfkASKJLKJsdfkjLKJLKDAsfkjs3+ test_user_2@my_friends_machine.local

(Note: Your personal public SSH key will appear on top and any additional keys should be pasted as new lines below)

Step 4:

• Save and exit out of the text editor.

Step 5:

• Repeat this process across all of your instances you would like to provide access to.

Done! 🎉

The newly added public key owner(s) should now be able to SSH into the instance(s) you've added them to. 

FAQ

1. Is there a limit to how many public keys I can add to a particular instance?

Answer: No, there is no limit. You can add as many public keys to an instance as you desire. (Note: Please be sure to only add trusted public keys to your instance(s))

2. How do I generate SSH keys (Public and Private keys)?

Answer: Simply run the following command:

ssh-keygen

This will generate a public and private key. The public key is typically stored at:

~/.ssh/id_rsa.pub

or 

~/.ssh/id_ed25519.pub

3. What is the difference between a public key and a private key?

Answer: A public key is used for encryption and can be shared with others. It is used to authenticate the user to the server. While a private key is used for decryption and should be kept secure. It is used to decrypt the data encrypted with the corresponding public key.