Avenuelucky

I'm trying to re-generate ssh host keys on a handful of remote servers via ansible (and ssh-keygen), but the files don't seem to be showing up. The playbook runs OK.

1. Github Generate Ssh Key Windows
2. Generate Ssh Rsa Key
3. Generate Ssh Key On A Cluster Line
4. Create Ssh Key Windows
5. Generate Ssh Key On A Cluster System
6. Generate Ssh Key Github
7. Generate Ssh Key On A Cluster System

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Introduction

SSH, or secure shell, is an encrypted protocol used to administer and communicate with servers. When working with a Debian server, chances are you will spend most of your time in a terminal session connected to your server through SSH.

In this guide, we’ll focus on setting up SSH keys for a vanilla Debian 10 installation. SSH keys provide an easy, secure way of logging into your server and are recommended for all users.

Step 1 — Create the RSA Key Pair

The first step is to create a key pair on the client machine (usually your computer):

By default ssh-keygen will create a 2048-bit RSA key pair, which is secure enough for most use cases (you may optionally pass in the -b 4096 flag to create a larger 4096-bit key).

After entering the command, you should see the following output:

Press enter to save the key pair into the .ssh/ subdirectory in your home directory, or specify an alternate path.

If you had previously generated an SSH key pair, you may see the following prompt:

Warning: If you choose to overwrite the key on disk, you will not be able to authenticate using the previous key anymore. Be very careful when selecting yes, as this is a destructive process that cannot be reversed.

You should then see the following prompt:

Here you optionally may enter a secure passphrase, which is highly recommended. A passphrase adds an additional layer of security to prevent unauthorized users from logging in. To learn more about security, consult our tutorial on How To Configure SSH Key-Based Authentication on a Linux Server.

You should then see the following output:

You now have a public and private key that you can use to authenticate. The next step is to place the public key on your server so that you can use SSH-key-based authentication to log in.

Step 2 — Copy the Public Key to Debian Server

The quickest way to copy your public key to the Debian host is to use a utility called ssh-copy-id. Due to its simplicity, this method is highly recommended if available. If you do not have ssh-copy-id available to you on your client machine, you may use one of the two alternate methods provided in this section (copying via password-based SSH, or manually copying the key).

Copying Public Key Using ssh-copy-id

The ssh-copy-id tool is included by default in many operating systems, so you may have it available on your local system. For this method to work, you must already have password-based SSH access to your server.

To use the utility, you simply need to specify the remote host that you would like to connect to and the user account that you have password SSH access to. This is the account to which your public SSH key will be copied.

The syntax is:

Github Generate Ssh Key Windows

You may see the following message:

This means that your local computer does not recognize the remote host. This will happen the first time you connect to a new host. Type “yes” and press ENTER to continue.

Next, the utility will scan your local account for the id_rsa.pub key that we created earlier. When it finds the key, it will prompt you for the password of the remote user’s account:

Type in the password (your typing will not be displayed for security purposes) and press ENTER. The utility will connect to the account on the remote host using the password you provided. It will then copy the contents of your ~/.ssh/id_rsa.pub key into a file in the remote account’s home ~/.ssh directory called authorized_keys.

You should see the following output:

At this point, your id_rsa.pub key has been uploaded to the remote account. You can continue on to Step 3.

Copying Public Key Using SSH

If you do not have ssh-copy-id available, but you have password-based SSH access to an account on your server, you can upload your keys using a conventional SSH method.

We can do this by using the cat command to read the contents of the public SSH key on our local computer and piping that through an SSH connection to the remote server.

On the other side, we can make sure that the ~/.ssh directory exists and has the correct permissions under the account we’re using.

We can then output the content we piped over into a file called authorized_keys within this directory. We’ll use the >> redirect symbol to append the content instead of overwriting it. This will let us add keys without destroying previously added keys.

The full command looks like this:

You may see the following message:

This means that your local computer does not recognize the remote host. This will happen the first time you connect to a new host. Type “yes” and press ENTER to continue.

Afterwards, you should be prompted to enter the remote user account password:

After entering your password, the content of your id_rsa.pub key will be copied to the end of the authorized_keys file of the remote user’s account. Continue on to Step 3 if this was successful.

Copying Public Key Manually

If you do not have password-based SSH access to your server available, you will have to complete the above process manually.

We will manually append the content of your id_rsa.pub file to the ~/.ssh/authorized_keys file on your remote machine.

To display the content of your id_rsa.pub key, type this into your local computer:

You will see the key’s content, which should look something like this:

Access your remote host using whichever method you have available.

Once you have access to your account on the remote server, you should make sure the ~/.ssh directory exists. This command will create the directory if necessary, or do nothing if it already exists:

Generate Ssh Rsa Key

Now, you can create or modify the authorized_keys file within this directory. You can add the contents of your id_rsa.pub file to the end of the authorized_keys file, creating it if necessary, using this command:

In the above command, substitute the public_key_string with the output from the cat ~/.ssh/id_rsa.pub command that you executed on your local system. It should start with ssh-rsa AAAA....

Finally, we’ll ensure that the ~/.ssh directory and authorized_keys file have the appropriate permissions set:

This recursively removes all “group” and “other” permissions for the ~/.ssh/ directory.

If you’re using the root account to set up keys for a user account, it’s also important that the ~/.ssh directory belongs to the user and not to root:

In this tutorial our user is named sammy but you should substitute the appropriate username into the above command.

We can now attempt passwordless authentication with our Debian server.

Step 3 — Authenticate to Debian Server Using SSH Keys

If you have successfully completed one of the procedures above, you should be able to log into the remote host without the remote account’s password.

The basic process is the same:

If this is your first time connecting to this host (if you used the last method above), you may see something like this:

This means that your local computer does not recognize the remote host. Type “yes” and then press ENTER to continue.

If you did not supply a passphrase for your private key, you will be logged in immediately. If you supplied a passphrase for the private key when you created the key, you will be prompted to enter it now (note that your keystrokes will not display in the terminal session for security). After authenticating, a new shell session should open for you with the configured account on the Debian server.

If key-based authentication was successful, continue on to learn how to further secure your system by disabling password authentication.

Step 4 — Disable Password Authentication on your Server

If you were able to log into your account using SSH without a password, you have successfully configured SSH-key-based authentication to your account. However, your password-based authentication mechanism is still active, meaning that your server is still exposed to brute-force attacks.

Before completing the steps in this section, make sure that you either have SSH-key-based authentication configured for the root account on this server, or preferably, that you have SSH-key-based authentication configured for a non-root account on this server with sudo privileges. This step will lock down password-based logins, so ensuring that you will still be able to get administrative access is crucial.

Once you’ve confirmed that your remote account has administrative privileges, log into your remote server with SSH keys, either as root or with an account with sudo privileges. Then, open up the SSH daemon’s configuration file:

Inside the file, search for a directive called PasswordAuthentication. This may be commented out. Uncomment the line and set the value to “no”. This will disable your ability to log in via SSH using account passwords:

Save and close the file when you are finished by pressing CTRL + X, then Y to confirm saving the file, and finally ENTER to exit nano. To actually implement these changes, we need to restart the sshd service:

As a precaution, open up a new terminal window and test that the SSH service is functioning correctly before closing this session:

Once you have verified your SSH service, you can safely close all current server sessions.

The SSH daemon on your Debian server now only responds to SSH keys. Password-based authentication has successfully been disabled.

Conclusion

You should now have SSH-key-based authentication configured on your server, allowing you to sign in without providing an account password.

If you’d like to learn more about working with SSH, take a look at our SSH Essentials Guide.

• 3Login with SSH keys

Overview

Windows does not come with a built-in SSH client.However you can download PuTTY for free.A very useful feature of PuTTY is it does not need to be installed, which allows it to be used on machines without administrative access.Simply run the putty.exe file.

Usage

To connect to the cluster, open putty and set your host name as NetID@login.storrs.hpc.uconn.edu. For example, 'abc12345@login.storrs.hpc.uconn.edu'.

To save you from having to enter this 'Host Name' line the next time you run PuTTY, type any name into the 'Saved Sessions' box and click the 'Save' button.Then when you next open PuTTY, just double click on the saved session in the list (under Default) to open the connection with your saved settings.

Also, the first time you connect, you will see a warning about the server's fingerprint.Click 'Yes' to accept the server's public key.

Generate Ssh Key On A Cluster Line

Now you will see a black terminal with your Net ID, prompting for your password.Type your Net ID (not engineering ID) password to log in to the cluster.That's it!Continue reading to automate your login to the cluster.

Login with SSH keys

We recommend generating SSH keys to save yourself time entering your NetID and password, not only for PuTTy, but for all of your OpenSSH aware programs.Download PuTTY gen to generate the keys.

Create key pair using PuTTY Key Generator

1. Run puttygen.exe and click on the 'Generate' button
2. After you move the mouse around to generate randomness and he green bar moves to completion, it will prompt for a Key passphrase. You can leave it blank.
3. Click 'Save public key' and then create the standard .ssh folder:
   1. Press the Ctrl+L keys to select the top location bar.
   2. Press Ctrl+A and then Backspace to clear the current folder name.
   3. Type %HOMEPATH% in that location bar and hit Enter.
   4. Click the 'New folder' button and type .ssh. and hit Enter (yes, you need the extra dot at the end).
   5. Double-click on the new '.ssh' folder and save your public key as id_rsa.pub
4. Click 'Save private key' and click 'Yes' to ignore the warning about saving the key without a passphrase.
   1. Type id_rsa.ppk and 'Save'

Create Ssh Key Windows

1. Click Conversions > Export OpenSSH key and click 'Yes' to ignore the warning about saving the key without a passphrase.
   1. Type id_rsa and 'Save'.
2. Leave the PuTTY Key Generator window open! We will use it later on.

Copy the public key to the cluster

Now let's copy the public key to the cluster to allow auto-login.

1. Go to your PuTTY window from your last session where you are logged into the cluster. If you don't see see [<NetID>@cn65 ~]$ then make sure you followed the previous steps to login using PuTTY. In the PuTTy window:
   1. Copy the line below from this wiki:

      nano ~/.ssh/authorized_keys

   2. Right click anywhere inside of your PuTTy window to paste, and then to run the command press Enter. This opens authorized_keys inside of the editor 'nano'.
   3. It's possible your file is empty, or you may see some 'ssh-rsa ...' lines. If you have some of those 'ssh-rsa ...' lines, press Alt+/ to move to the last line of the file. If your cursor is not at the beginning of a new line, press Enter to create a new line.
2. Go back to your still open PuTTy Key Generator window and click inside of the scrolling window where it says 'Public key for pasting into OpenSSH authorized_keys file'
   1. Press Ctrl+HOME then Ctrl+SHIFT+END and right-click > Copy.
   2. To paste in the cluster window, just right-click again in the cluster window.
   3. In the cluster window, save the file with Ctrl+O Enter Ctrl+X
3. Close the cluster window and choose OK to close the session.

Tell PuTTy to use the private key

Now that the cluster knows to allow our key, we just have to tell PuTTy to use the key during login.

Generate Ssh Key On A Cluster System

1. Open PuTTy again: choose your Saved 'login' Session on the main screen and click 'Load'.
   1. Double-click on SSH in the left-side menu.
   2. Click on Auth
   3. Browse for the private key. Putty should automagically open to the .ssh folder in your home directory, where you can choose your new id_rsa.ppk file
2. To save your session, in the left side window scroll to the top and click on Session, choose 'login' and click 'Save'.
3. Test that it works by clicking 'Open' and you should automatically be logged in without having to type your password!

Generate Ssh Key Github

Next Steps

Generate Ssh Key On A Cluster System

You can continue reading about submitting jobs from the SLURM Guide and the HPC Software Guides.