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How to replace an SSH key pair on a Public Cloud instance
Find out how restore server access by replacing an SSH key pair with a new one in case your private key is lost
2024-06-13

Objective

Losing your private SSH key means losing access to your instance if you have not configured an alternative way of access.

However, you can still connect to your instance via the OVHcloud rescue mode, which allows you to log in with a provisional password and modify your files.

This guide explains how to replace your SSH keys if you have lost access to your instance.

Warning

OVHcloud provides services for which you are responsible with regard to their configuration and management. It is therefore your responsibility to ensure that they function correctly.

This guide is designed to assist you in common tasks as much as possible. Nevertheless, we recommend contacting a specialist service provider or reaching out to our community if you experience any issues.

Requirements

Instructions

Step 1: Create a new key pair

Create a new SSH key pair on your local device, as described in the first part of the SSH key guide.

Step 2: Access your instance in rescue mode

Follow the steps in the rescue mode guide to reboot the instance into rescue mode, connect to it and mount your partitions.

Once you have used the mount command as described in the guide and your system partition is accessible, you can use the following command:

chroot path/to/partition/mountpoint

The file path is dependent on the mountpoint you used. If you have mounted your partition at /mnt, you would enter the following:

chroot /mnt/

You should now have full write access to your files in this folder.

Step 3: Replace the key

Open the "authorized_keys" file concerned with a text editor. This file stores SSH keys and is located in the home folder of the user with which you connect to your instance.

Example:

nano /mnt/home/USER_NAME/.ssh/authorized_keys

Replace "USER_NAME" with your actual user name.

Copy and paste your new public key (created in step 1) into the file. It should look similar to the following example:

ssh-rsa 1111111111122222222222333333333333444444444555555555556666666666
777777777778888888888999999900000000000000000000000000== old@sshkey
ssh-rsa AAAAAAAAABBBBBBBBBBBCCCCCCCCCCCCCCCCDDDDDDDDDDDDDDDDDDDEEEEEEEEE
EEFFFFFFFFFFFFFGGGGGGGGGGGGGhhhhhhhhhhhhhhhhhhhhhhhhhh== new@sshkey

For security reasons, delete the obsolete "old" key string from the file. Save your changes and exit the editor.

Restart the instance in "normal" mode from your OVHcloud Control Panel. Refer to the rescue mode guide if needed.

You have now access to the instance with your new SSH key pair.

Go further

Join our community of users.