Adding a Server to known_hosts SSH

Hello Dev, welcome to this journal article where we will guide you on how to add a server to known_hosts SSH. If you want to securely connect to a remote server through SSH, you need to add it to known_hosts. This will ensure you are connecting to the right server and protect you from man-in-the-middle attacks. In this article, we will give you a step-by-step guide on how to add a server to known_hosts SSH, and answer some frequently asked questions.

What is known_hosts?

Known_hosts is a file where SSH stores public keys of remote servers you have connected to before. When you connect to a remote server, SSH will compare the public key of the server with the one stored in known_hosts. If they match, you can proceed with the connection. If they don’t match, SSH will warn you and ask for your confirmation before allowing the connection.

Here’s how to add a server to known_hosts SSH:

Step 1: Open Terminal

The first step is to open your terminal. You can do this by pressing CTRL + ALT + T on Linux or Command + Spacebar and typing Terminal on Mac.

Step 2: Identify the Server

You need to identify the server you want to add to known_hosts. This can be done by obtaining the server’s IP address or hostname.

If you have the IP address, you can use the following command:

Command
Description
ssh-keyscan 192.168.0.1
Retrieve public key from IP address 192.168.0.1

If you have the hostname, you can use the following command:

Command
Description
ssh-keyscan example.com
Retrieve public key from hostname example.com

Step 3: Add Server to known_hosts

Now that you have the public key of the server, you can add it to known_hosts using the following command:

Command
Description
ssh-keygen -H -F 192.168.0.1 >> ~/.ssh/known_hosts
Add public key of IP address 192.168.0.1 to known_hosts file
ssh-keygen -H -F example.com >> ~/.ssh/known_hosts
Add public key of hostname example.com to known_hosts file

Congratulations! You have successfully added a server to known_hosts SSH. From now on, when you connect to this server, SSH will verify the public key and protect you from man-in-the-middle attacks.

FAQ

What if the Server’s Public Key Changes?

If the public key of the server changes, SSH will warn you and ask for your confirmation before allowing the connection. This can happen if the server’s operating system is reinstalled, or if the server is compromised. In this case, you should investigate why the public key has changed before confirming the connection.

Can I Remove a Server from known_hosts?

Yes, you can remove a server from known_hosts using the following command:

Command
Description
ssh-keygen -R 192.168.0.1
Remove IP address 192.168.0.1 from known_hosts file
ssh-keygen -R example.com
Remove hostname example.com from known_hosts file
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What if I Want to Connect to a Server with a Dynamic IP?

If you want to connect to a server with a dynamic IP, you can use its hostname instead. If the server’s hostname changes frequently, you can create an alias in your SSH configuration file. Here is an example:

Command
Description
Host myserver
Define an alias called myserver
Hostname example.com
The actual hostname of the server

Now you can connect to the server using the alias myserver instead of its hostname.

Conclusion

Adding a server to known_hosts SSH is essential if you want to securely connect to remote servers through SSH. By following the simple steps we have outlined in this article, you can add a server to known_hosts and protect yourself from man-in-the-middle attacks. If you have any more questions, feel free to ask.