Copy SSH Host Key to New Server

Hello Dev, if you are here, it is likely that you have encountered a situation where you need to copy SSH host key to a new server. This can be a crucial task especially if you are dealing with sensitive information. In this journal article, we will guide you on how to transfer SSH host key to a new server without compromising its integrity.

Understanding SSH Host Key

Before we delve into the process of copying SSH host key to a new server, it’s important that we understand what SSH host key is.

SSH host key is a cryptographic key that is used to authenticate a server to a client. It is a combination of a public and private key pair that is unique to every server. When a client connects to a server, the server presents its public key and the client verifies it by matching it with the stored private key. This ensures that the client is connected to the correct server and not an imposter.

Now that we know what SSH host key is, let’s move on to the process of copying it to a new server.

Process of Copying SSH Host Key to a New Server

Copying SSH host key to a new server is a simple process, which involves three main steps: generating a new host key on the new server, copying the host key from the old server to the new server, and updating the SSH configuration file on the new server.

Step 1: Generating a New Host Key on the New Server

The first step is to generate a new SSH host key on the new server. This can be achieved by running the following command:

This will generate a new RSA host key on the new server and save it to the specified location. You can use the same command to generate a different type of host key, such as DSA or ECDSA if required.

Step 2: Copying the Host Key from the Old Server to the New Server

The second step involves copying the host key from the old server to the new server. You can achieve this by running the following command on the old server:

This command will copy the public key from the old server to the /tmp directory on the new server. You will be prompted to enter the password for the user account on the new server.

Step 3: Updating the SSH Configuration File on the New Server

The third and final step involves updating the SSH configuration file on the new server to use the new host key. You can achieve this by running the following command:

This command will copy the public key from the /tmp directory on the new server to the authorized_keys file in the home directory of the specified user account. This will allow the user to connect to the new server using the new host key.

FAQ

What happens if I don’t copy the SSH host key to a new server?

If you don’t copy the SSH host key to a new server, the client will not be able to authenticate the server and will receive a warning message. This could lead to security issues as the client might connect to an imposter server.

Can I use the same host key on multiple servers?

No, you cannot use the same host key on multiple servers as it is unique to every server. Each server should have its own host key pair.

Can I use a different type of host key?

Yes, you can use a different type of host key such as DSA or ECDSA if required. You can generate a different type of host key by specifying the type and bit length in the ssh-keygen command.

Can I copy the host key using a different method?

Yes, you can copy the host key using a different method such as rsync or FTP. However, the method described in this article is the most secure and recommended method.

Do I need to update the SSH configuration file on the old server?

No, you do not need to update the SSH configuration file on the old server as it will continue to use the old host key. The old server will only be used until the migration is complete.

Congratulations! You have successfully learned how to copy SSH host key to a new server. We hope this article has been helpful. If you have any queries or feedback, please feel free to reach out to us.