Hey there Dev! Are you struggling with the error message “server not found in known_hosts” while connecting to your server? Don’t worry, you’re not alone. This error message can be confusing and frustrating, especially for beginners. But don’t worry, in this comprehensive guide, we’ll cover everything you need to know about this error message and how to fix it.
What is known_hosts?
Before we dive into the “server not found in known_hosts” error message, let’s first understand what known_hosts is. Known_hosts is a file in your SSH directory that contains a list of all the servers that your machine has connected to and verified the host key for. This is done to prevent a man-in-the-middle (MITM) attack. When you try to connect to a server, SSH checks the server’s host key against the one in your known_hosts file to ensure that you’re connecting to the right server.
Why do we need known_hosts?
Known_hosts is an essential part of SSH. It prevents attackers from intercepting your connection and posing as the server. This is done through a process called host key verification, which involves comparing the server’s host key with the one stored in your machine’s known_hosts file. The host key is a unique identifier that’s used to verify that the server you’re connecting to is the one you intended to connect to. Without this verification, there’s a risk that an attacker could intercept your connection and steal your data or carry out other malicious activities.
Where is known_hosts located?
The known_hosts file is located in your SSH directory. The location of this directory depends on the operating system you’re using. If you’re using Linux or macOS, the directory is usually located in the ~/.ssh directory. If you’re using Windows, the directory is usually located in the C:\Users\username\.ssh directory.
What happens if a host key changes?
If the host key of a server changes, SSH will display a warning message and ask if you want to connect to the server. If you’re not sure why the host key has changed, it’s best to contact the system administrator of the server to verify the change. If you’re confident that the server has changed its host key for a legitimate reason, you can update your known_hosts file to include the new key.
What is the “server not found in known_hosts” error message?
The “server not found in known_hosts” error message occurs when SSH is unable to find the host key for a server in your known_hosts file. This can happen for a variety of reasons, including:
Reasons for the error message |
The server is new and you haven’t connected to it before |
You’re connecting to the server from a different machine |
You’ve deleted the server’s entry from your known_hosts file |
The server’s host key has changed |
What does the error message mean?
When you see the “server not found in known_hosts” error message, it means that SSH is unable to verify the server’s host key. This could be because the key is missing from your known_hosts file or because the key has changed since you last connected to the server. In either case, SSH is unable to establish a secure connection to the server and will refuse to connect.
What should you do when you see the error message?
When you see the “server not found in known_hosts” error message, you have a few options:
- You can add the server’s host key to your known_hosts file manually
- You can delete your existing known_hosts file and allow SSH to create a new one
- You can connect to the server with the “-o StrictHostKeyChecking=no” option to bypass host key verification
How do you add a host key to your known_hosts file?
To add a host key to your known_hosts file, you’ll need to connect to the server and verify the host key manually. You can do this by running the following command:
ssh-keyscan <server> >> ~/.ssh/known_hosts
This will append the server’s host key to your known_hosts file. Note that you should only do this if you’re confident that the server you’re connecting to is legitimate.
How do you delete your existing known_hosts file?
If you want to delete your existing known_hosts file and allow SSH to create a new one, you can do so by running the following command:
rm ~/.ssh/known_hosts
This will delete your existing known_hosts file. The next time you connect to a server, SSH will create a new file and add the server’s host key to it.
How do you connect to a server without host key verification?
If you want to connect to a server without host key verification, you can use the “-o StrictHostKeyChecking=no” option. This will tell SSH to connect to the server without verifying its host key. Note that this is not recommended, as it can leave you vulnerable to a man-in-the-middle attack.
Conclusion
So there you have it, Dev! Everything you need to know about the “server not found in known_hosts” error message. Remember, host key verification is an essential part of SSH and helps to keep your connections secure. If you do encounter this error message, it’s best to take the time to verify the server’s host key and add it to your known_hosts file manually. Stay safe and happy coding!
FAQ
Q. Why does the host key change?
The host key can change if the server’s configuration changes or if the server is reinstalled or reconfigured. It can also change if an attacker tries to intercept your connection and poses as the server.
Q. What is a man-in-the-middle attack?
A man-in-the-middle (MITM) attack is a type of cyber attack where an attacker intercepts your connection and poses as the server. This allows the attacker to steal your data or carry out other malicious activities.
Q. Is it safe to connect to a server without host key verification?
No, it’s not safe to connect to a server without host key verification. This leaves you vulnerable to a man-in-the-middle attack.
Q. How do I know if a server’s host key has changed?
If a server’s host key has changed, SSH will display a warning message when you try to connect to the server. If you’re not sure why the host key has changed, it’s best to contact the system administrator of the server to verify the change.
Q. Can I use SSH without known_hosts?
Yes, you can use SSH without a known_hosts file, but this is not recommended. Without host key verification, you’re leaving yourself vulnerable to a man-in-the-middle attack.
Related Posts:- The Server's Host Key Was Not Found in the Cache: Everything… Dear Dev, are you tired of encountering the server's host key not found in the cache error message? This error message can be frustrating and confusing, especially when you're trying…
- How to Fix "Paramiko Server Not Found in Known_Hosts" Error Hello Dev! Are you facing the "Paramiko Server Not Found in Known_Hosts" error while trying to connect to a remote server? Don't worry, you're not alone. This error occurs when…
- Paramiko.ssh_exception.sshexception server not found in… Greetings Dev! Have you been experiencing the error message paramiko.ssh_exception.sshexception server not found in known_hosts? This can be a frustrating problem, but fear not! In this article, we will dive…
- How to Add a Server to known_hosts using ssh - Dev's Guide Welcome Dev! In this article, we are going to show you how to add a server to your known_hosts file using ssh. This guide is intended for those who are…
- Host Key for Server Does Not Match: Understanding the Issue… Hello Dev, have you ever come across the error message "host key for server does not match" while trying to access a remote machine or server through SSH? If yes,…
- 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…
- How to Add a Server to Known_Hosts: A Comprehensive Guide… Dear Devs, Are you tired of constantly typing in your server's password every time you connect? Do you wish there was an easier way to access your server? Look no…
- The Ultimate Guide to Fixing "Server's Host Key has been… Welcome, Dev! It's not uncommon to face errors and issues when working with servers. One of the most frustrating errors that you may encounter is the "Server's host key has…
- How to Fix the "Server's Host Key Did Not Match the… Welcome to this journal article, Dev. In this article, we will discuss the common error message "Server's Host Key Did Not Match the Signature Supplied" that you might encounter while…
- The Server's Host Key Does Not Match The One Cached Hello Dev, we are glad to have you here. Today, we will be discussing one of the most common errors faced by server administrators - "the server's host key does…
- The Server's Host Key is not Cached in the Registry: A… Hello Dev! Are you encountering the error message "The server's host key is not cached in the registry" while connecting to your server? This error can be quite frustrating, especially…
- The Server's Host Key Failed to Verify: Understanding and… Hey Dev, have you ever experienced receiving an error message "The server's host key failed to verify" while connecting to a remote server through SSH? This error can be frustrating…
- How to Fix "Server's Host Key is Invalid" Error Greetings Dev, in this article we'll be discussing how to solve the "server's host key is invalid" error that you might have encountered while trying to connect to your server.…
- The Server's Host Key is Not Cached: A Comprehensive Guide… Hello Dev! In this article, we will discuss one of the common issues encountered in SSH connections - "The server's host key is not cached." We will explore what this…
- Host Key for Server Changed: What Dev Needs to Know Dear Dev, if you have been managing servers, you may have come across a message that says: "WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!" This warning is a result of the…
- Server Host Key Did Not Match the Signature Supplied: A… Greetings, Devs! In this article, we will tackle the common issue of "server host key did not match the signature supplied" and provide you a comprehensive guide to resolving it.…
- How to Fix "Signature from Server's Host Key is Invalid" Greetings, Dev! Are you experiencing issues with your SSH connection? Are you seeing the error message "signature from server's host key is invalid"? Well, fear not, as we have gathered…
- The Server Host Key is Not Cached - A Comprehensive Guide… Dear dev, are you experiencing issues with your server host key not being cached? Don't worry, you've come to the right place. In this article, we will provide you with…
- How to Get Host Key from SFTP Server Hello Dev, welcome to our journal article about getting host key from SFTP server. In this article, we will provide a comprehensive guide on how to obtain the host key…
- How to Get Known Host Key from SFTP Server Hello Dev, have you ever encountered a warning message when connecting to an SFTP server stating that the server's host key is unknown? This message can be quite alarming if…
- Understanding Server Host Key: A Guide for Dev Hello, Dev! Are you familiar with server host key? It is an essential aspect of secure communication between client and server. This guide will help you understand server host key,…
- No Active Checks on Server Host Not Found Hello Dev, are you experiencing server issues with no active checks on server host not found? If so, you're not alone. This problem can be frustrating and confusing, but don't…
- Connect to Message Server Host Failed - Troubleshooting… Greetings Dev! As a developer, you might have encountered the error message "Connect to Message Server Host Failed" while trying to connect to a message server host. This error can…
- Fixing Lost Connection to Host Server Connection Timed Out… Hello Dev, have you ever experienced connecting to a server but encountering a "lost connection to host server connection timed out" error? This error message can be frustrating, especially if…
- Resolving "Unable to Resolve Server Address No Such Host Is… Hello Dev! Are you encountering an error message that says "Unable to resolve server address no such host is known" while trying to access a website? If so, don't worry!…
- Apache Server 404: Everything You Need to Know 🚫 Error 404: Page Not FoundGreetings, dear readers! Have you ever encountered the frustrating message "404 Not Found" while browsing a website? Well, you're not alone. This error message is…
- Understanding the 550 5.1 2 Host Unknown Name Server Error… Dear Dev, have you ever encountered the error message “550 5.1 2 Host Unknown Name Server” while sending an email? This error message is common among email users, especially those…
- The Host is Already Connected to This vCenter Server: A… Hey Dev! Are you getting the error message "The host is already connected to this vCenter server" while trying to connect to your vCenter server? Don't worry, you're not alone!…
- Fixing "Server with specified host name could not be found"… Welcome, Dev! Have you ever encountered a "server with specified host name could not be found" error while browsing the web? It can be a frustrating experience, especially if you're…
- Dealing with "Host is not allowed to connect to this MySQL… Hello Dev! If you are reading this article, chances are you have been seeing the "Host is not allowed to connect to this MySQL server" error message and you are…