Linux ssh host key verification failed

SSH «Host key verification failed»

I am supposed to put up a file on a server from my own computer with ssh as a school assignment. It has been a slow process but now I’m stuck. I have googled but not found anything that has helped. As I am a total beginner at this it is probably some stupid fault of mine, so please help me out (easy instructions, expect me to do it wrong 😉 ) . Below is the terminal text from where I am stuck, I have tried both logged in on my computer and logged in on the server. logged in on the server:

teddy@rymd-srv:~$ ssh-keygen -R teddy@elev.rymdgymnasiet.com /home/teddy/.ssh/known_hosts updated. Original contents retained as /home/teddy/.ssh/known_hosts.old teddy@rymd-srv:~$ scp -r teddy@85.226.40.57:/home/teddy/Pictures/filetransfer.jpeg teddy@elev.rymdgymnasiet.com:/home/teddy teddy@85.226.40.57's password: Host key verification failed. lost connection 

teddy@TeddysDator:~$ ssh-keygen -R teddy@elev.rymdgymnasiet.com /home/teddy/.ssh/known_hosts updated. Original contents retained as /home/teddy/.ssh/known_hosts.old teddy@TeddysDator:~$ scp -r teddy@85.226.40.57:/home/teddy/Pictures/filetransfer.jpeg teddy@elev.rymdgymnasiet.com:/home/teddy The authenticity of host '85.226.40.57 (85.226.40.57)' can't be established. ECDSA key fingerprint is ef:9c:4c:41:3c:9d:b1:40:05:67:30:34:e8:d3:ab:c6. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added '85.226.40.57' (ECDSA) to the list of known hosts. teddy@85.226.40.57's password: Host key verification failed. lost connection 

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Fix “Host key verification failed”

“Host key verification failed” is a common error message that can occur when trying to connect to a remote server via Secure Shell (SSH). This error can be frustrating, but it’s actually a security feature that can be easily resolved. In this blog post, we will first look at how to fix this error, then explain what it means and why it’s important.

How to Fix “Host Key Verification Failed” Error

The first step in fixing this error is to remove the incorrect host key from your SSH client’s known_hosts file. To do this, run the following command in your terminal:

Replace with the hostname or IP address of the remote server you’re trying to connect to. This will remove the incorrect host key from your known_hosts file.

For example: ssh-keygen -R add-domain-name.com or using the server IP address: ssh-keygen -R 123.123.12.3

Next, try to connect to the remote server again using the following command:

Replace with your username on the remote server, and replace with the hostname or IP address of the remote server.

When you run this command, you should see a warning message similar to the following:

The authenticity of host ' ()' can't be established. RSA key fingerprint is . Are you sure you want to continue connecting (yes/no)?

Type yes and press Enter to continue. You should now be connected to the remote server, and the host key for that server should be added to your known_hosts file.

Manually fixing the error

Instead of using the above commands, you can also manually fix this error. This is because the error output itself tells the exact path, filename, and line location of the failed key. So, for example, if the incorrect host key is on line 1 of your known_hosts file, you can manually fix the error by editing the file:

1. Open your known_hosts file in a text editor. The file is usually located at ~/.ssh/known_hosts .
   for example sudo nano ~/.ssh/known_hosts .
2. Locate the line # with the incorrect host key. In this case, it should be on line 1.
3. Delete the line with the incorrect host key.
4. Save the changes to the known_hosts file.
   Press Ctrl+O then Ctrl+X using nano. Or for vi or vim, use :wq .
5. Lastly, try to connect to the remote server again.

What Does “Host Key Verification Failed” Mean?

The “Host Key Verification Failed” error message occurs when the host key for a remote server does not match the host key stored in your SSH client’s known_hosts file.

When you connect to a remote server for the first time using SSH, the host key for that server is added to your known_hosts file. This host key is used to verify the identity of the remote server whenever you connect to it in the future.

If the host key for the remote server changes, for example, because the server was reinstalled or because its IP address changed, you will get the “Host Key Verification Failed” error message. This error message is a warning that the remote server you’re trying to connect to may not be the server you think it is.

For instance, GitHub recently changed its RSA SSH host key, which is used to secure Git operations for GitHub.com, leading to the “Host Key Verification Failed” error for many users attempting to connect.

Why Is Host Key Verification Important?

Host key verification is important because it helps to prevent man-in-the-middle attacks. A man-in-the-middle attack is a type of security attack where a third party intercepts and modifies the communication between two parties.

In a man-in-the-middle attack, an attacker could intercept the communication between your SSH client and the remote server and replace the host key for the remote server with the host key for a different server that the attacker controls.

If you connect to the remote server without verifying the host key, you may be sending sensitive information to the attacker’s server instead of the real remote server.

By verifying the host key for a remote server, you can ensure that you are communicating with the real remote server and not an attacker’s server. This helps to keep your data and information secure.

Conclusion

In conclusion, the “Host Key Verification Failed” error message is a security feature that helps to protect your data and information. By following the steps outlined above, you can easily resolve the error and maintain the security of your connections to remote servers.

It’s important to understand the significance of host key verification and to always verify the host key whenever you connect to a remote server for the first time or if you receive the “Host Key Verification Failed” error message.

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What Does “Host Key Verification Failed” Mean?

While using ssh server, one of the common errors you’ll encounter is “Host key verification failed”. To understand why this error occurs, let’s first understand how ssh establishes a connection.

When you attempt to connect to a remote server, the server asks you to confirm if you are trying to establish connection to the right server.

If you type “yes”, the client will add the public host key to the “.ssh/known_hosts” file. Once the remote server’s key is added, the next time you try to connect to the same server, the client will compare the keys with the keys stored in the “known_hosts” file.

You will not be prompt with any warning if the key is present in the “known_hosts” file. The server will be connected right away.

Why the “Host key verification failed” Error Occurs

The primary reason that causes the “Host key verification failed” error is that the remote host key has been changed and no longer the same as stored in the “known_hosts” file. The key usually changes when servers are rebuilt, and you get an error as shown below:

How to Fix the “Host key verification failed” Error

To fix this error, we need to delete the offending key from the “known_hosts” file present in our system in “.ssh” directory. The error gives you the remote server’s IP address and the line number on which the key is stored in the “known_hosts” file.

In the above error, “/home/user/.ssh/known_hosts:7”, the “:7” is the offending line number. Multiple approaches to fix this error are listed below:

Method 1:

The first method to fix this error is using the “sed” command. The “sed” command is used to modify the text files to search, add or delete something from the files. We are using it to delete the offending host:

Where “7” is the line number shown in the above error, your line number might be different; ensure that you use the correct line number. The command will delete the offending line from the “known_hosts” file and resolve the issue.

Method 2:

The second approach is opening the “known_hosts” file in any editor:

And manually delete the offending line and save the file.

Method 3:

The third method is removing the server using the “ssh-keygen” command. Follow the syntax mentioned below:

For instance, to remove the host key of “192.168.10.116”, use:

Conclusion

The host key verification error occurs when the key of the remote server changes and client does not verify it from the stored keys. Server keys are stored in the “known_hosts” file on the client-side, and upon establishing the connection, the client verifies the key by comparing it with the keys stored in the “known_host” file and upon failing, you get a “Host key verification failed” error.

To rectify this, remove the offending host from the “known_hosts” file. This guide mentioned three different methods to remove the offending host and any method can be used to resolve this error.

About the author

Sam U

I am a professional graphics designer with over 6 years of experience. Currently doing research in virtual reality, augmented reality and mixed reality.
I hardly watch movies but love to read tech related books and articles.

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Что означает “Host Key Verification Failed”

П ри использовании ssh-сервера вы можете столкнуться с одной из распространенных ошибок: «Host Key Verification Failed». Чтобы понять, почему возникает эта ошибка, давайте сначала разберемся, как ssh устанавливает соединение.

Когда вы пытаетесь подключиться к удаленному серверу, сервер просит вас подтвердить, пытаетесь ли вы установить соединение с правильным сервером.

Если вы наберете «да», клиент добавит открытый ключ хоста в файл «.ssh/known_hosts». После добавления ключа удаленного сервера в следующий раз, когда вы попытаетесь подключиться к тому же серверу, клиент сравнит ключи с ключами, хранящимися в файле «known_hosts».

Вы не получите никаких предупреждений, если ключ присутствует в файле «known_hosts». Сервер будет подключен сразу.

Почему возникает ошибка «Host Key Verification Failed»

Основная причина, вызывающая ошибку Host Key Verification Failed», заключается в том, что ключ удаленного хоста был изменен и больше не тот, который хранится в файле «known_hosts». Ключ обычно меняется, когда серверы перестраиваются, и вы получаете сообщение об ошибке, как показано ниже:

Как исправить ошибку «Host Key Verification Failed»

Чтобы исправить эту ошибку, нам нужно удалить неверный ключ из файла «known_hosts», находящегося в нашей системе в каталоге «.ssh». Ошибка дает вам IP-адрес удаленного сервера и номер строки, в которой хранится ключ в файле «known_hosts».

В приведенной выше ошибки, «/home/user/.ssh/known_hosts:7», то «: 7» является задеть номер строки. Ниже перечислены несколько подходов к исправлению этой ошибки:

Способ 1:

Первый способ исправить эту ошибку — использовать команду sed. Команда «sed» используется для изменения текстовых файлов для поиска, добавления или удаления чего-либо из файлов. Мы используем его для удаления хоста-нарушителя:

Если «7» — это номер строки, показанный в приведенной выше ошибке, ваш номер строки может быть другим; убедитесь, что вы используете правильный номер строки. Команда удалит неправильную строку из файла «known_hosts» и решит проблему.

Способ 2:

Второй подход — открыть файл «known_hosts» в любом редакторе:

И вручную удалите оскорбительную строку и сохраните файл.

Способ 3:

Третий метод — удаление сервера с помощью команды «ssh-keygen». Следуйте синтаксису, указанному ниже:

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