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How to Replace Your Lost SSH Key Pair

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Stephanie Richards
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Learn how to configure the authorized_keys file for the admin user so that you can add a new SSH key to regain access to your instance.

If you have lost your SSH key, you might be unable to connect to your Public Cloud Instance if you have not configured any alternative way to do so.

To regain access, we have provided you with a rescue mode, which allows you to log in with a password and then change your files.

Requirements

Instructions

NOTE: If you would like to store an SSH key in the OVHcloud Control Panel, we recommend using RSA or ECDSA encryption. ED25519 is currently not supported.

After mounting your instance's disk in rescue mode, you will be able to access all your files. The file containing your SSH keys is shown below:

/mnt/home/USER_NAME/.ssh/authorized_keys

If you want to add your new SSH key, you just have to edit this file as follows:

admin@instance:~$ sudo vim /mnt/home/USER_NAME/.ssh/authorized_keys

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

Change the SSH key for the default user

To change your default user's SSH key, you just have to go to the user's personal file.

For example, for the admin user, the file you need is in the following folder:

/home/admin/.ssh/authorized_keys

For an Ubuntu instance, the default user will be "ubuntu" and the file will therefore be in the following folder:

/home/ubuntu/.ssh/authorized_keys

Change the password for the default user

You can also change your default user's password by using rescue mode and the following commands (if the user is admin).

First, change the root directory so that it is placed directly on the instance's disk:

NOTE: In the example below, we have used vdb1 as the name of the server's disk and mnt as the mount point.
root@instance:/home/admin# mount /dev/vdb1 /mnt/
root@instance:/home/admin# chroot /mnt/

Then change the admin password.

root@instance:/# passwd admin

Once this change has taken place and been backed up, you need to reboot your instance on its disk, so that you can log in with your new SSH key.

 

Go further

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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