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How to configure additional SSH keys on an instance

Stephanie R.
Updated

Learn how to configure additional SSH keys for connections to your instance.

When creating an instance in the OVHcloud Control Panel, you can add only one SSH key for the preconfigured user account. To log on to your instance with other use accounts, you can create more keys and add them to the instance in a few steps.

NOTE: OVHcloud provides services for which you are responsible for their configuration and management. You are therefore responsible for their proper functioning.

This tutorial is designed to help you as much as possible with common tasks. If you are having difficulty performing these actions, please contact a specialized service provider. OVHcloud can't provide you with technical support in this regard.

 

Requirements

 

Instructions

We currently support the following SSH key formats: RSA, ECDSA and ED25519.

Note that the instructions below are for general use, based on an Ubuntu server OS. Some commands may require customization for the distribution or operating system you are using.

Step 1: Create a new SSH key pair

If necessary, use our SSH key guide to create a new SSH key pair.

You can also find information on managing multiple keys on your local device if your setup requires it.

 

Step 2: Configure a new user account

Connect to your instance and use the commands below to create a new user account and .ssh folder:

sudo adduser user2
info: Adding user `user2' ...
info: Selecting UID/GID from range 1000 to 59999 ...
info: Adding new group `user2' (1003) ...
info: Adding new user `user2' (1003) with group `user2 (1003)' ...
info: Creating home directory `/home/user2' ...
info: Copying files from `/etc/skel' ...
New password: 
Retype new password:
passwd: password updated successfully
Changing the user information for user2
Enter the new value, or press ENTER for the default
        Full Name []:
        Room Number []:
        Work Phone []: 
        Home Phone []: 
        Other []: 
Is the information correct? [Y/n] y
info: Adding new user `user2' to supplemental / extra groups `users' ...
info: Adding user `user2' to group `users' ...
sudo mkdir /home/user2/.ssh/

Without further steps, the user account user2 in this example has no elevated permissions. If you need to grant this account root privileges on your instance, add it to the sudo group:

sudo usermod -aG sudo user2

You can learn more about user permissions and related topics in our user account guide.

 

Step 3: Add the public SSH key to your instance

Transferring public keys created on systems based on GNU/Linux, MacOS, or BSD

If you have created your SSH key pairs on a GNU/Linux, MacOS or BSD based system, you can use the command ssh-copy-id to add the public keys to your server.

The ssh-copy-id utility copies public keys to the file ~/.ssh/authorized_keys on the specified remote server and will automatically create the file in this directory if necessary.

ssh-copy-id username@IP_ADDRESS

By default, ssh-copy-id will try to transfer all public keys inside your local user's ~/.ssh directory. In order to add a single public key, you can specify this key file with the option -i followed by the file path:

ssh-copy-id -i ~/.ssh/KeyFileName username@IP_ADDRESS

Example:

ssh-copy-id -i ~/.ssh/myInstance_rsa.pub user2@203.0.113.102

You will be prompted for the user's password. If the process was successful, you will receive a message similar to the one below.

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'user@server-ip'"
and check to make sure that only the key(s) you wanted were added.

If you receive an error message instead, you can always add your public keys manually by following the steps described below.

As a best practice and for security reasons, a key pair should not be used by multiple users. Since each user on GNU/Linux systems has their own authorized_keys file in ~/.ssh/, you can use the command ssh-copy-id as shown above and adapt KeyFileName and user after you have created the key pair.

 

Adding public keys to the instance manually

Connect to your instance and open the file authorized_keys in the personal folder of the new user with your preferred text editor (nano is used in this example):

sudo nano /home/user2/.ssh/authorized_keys

Paste the public key string into this file. Save the file and exit the editor.

Reboot your instance (sudo reboot) or only restart the OpenSSH service with one of the following commands (the appropriate command may vary depending on your OS):

sudo systemctl restart ssh
sudo systemctl restart sshd

The new user can now connect to the instance from the device that stores the corresponding private SSH key:

ssh username@IP_ADDRESS

Example:

ssh user2@203.0.113.102

Consult the SSH key guide to learn more about using SSH keys with Public Cloud instances.

 

Go further

How to create Public Cloud instances

How to replace an SSH key pair on a Public Cloud instance with rescue mode

For more information and tutorials, please see our other Public Cloud support guides or explore the guides for other OVHcloud products and services.

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