1. Dec 18, 2019  Using SSH keys is more secure and convenient than traditional password authentication. In this tutorial, we will walk through how to generate SSH keys on Ubuntu 18.04 machines. We will also show you how to set up an SSH key-based authentication and connect to your remote Linux servers without entering a password. Creating SSH keys on Ubuntu #.
2. SSH keys are a way to identify trusted computers, without involving passwords. The steps below will walk you through generating an SSH key and adding the public key to the server. Step 1: Check for SSH Keys First, check for existing SSH keys on your computer. Open Git Bash, Cygwin, or Terminal, etc.
3. Jun 22, 2012  SSH keys provide a more secure way of logging into a virtual private server with SSH than using a password alone. With SSH keys, users can log into a server without a password. This tutorial explains how to generate, use, and upload an SSH Key Pair.

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SSH keys are a necessity for Python development when you are working withGit, connecting to remote servers and automating yourdeployments. Let's walk through how to generate SSHkey pairs, which contain both a public and a private key within a singlepair, on Ubuntu Linux.

Generating the Public and Private Keys

More information on SSH keys can be found here. You can generate an SSH key pair directly in cPanel, or you can generate the keys yourself and just upload the public one in cPanel to use with your hosting account. When generating SSH keys yourself under Linux, you can use the ssh-keygen command. To do so follow these steps: Open up the Terminal.

Open up a new terminal window in Ubuntu like we see in the followingscreenshot.

The ssh-keygen command provides an interactive command line interface forgenerating both the public and private keys. Invoke ssh-keygen with thefollowing -t and -b arguments to ensure we get a 4096 bit RSA key.Optionally, you can also specify your email address with -C (otherwiseone will be generated off your current Linux account):

(Note: the -o option was introduced in 2014; if this command fails for you, simply remove the -o option)

The first prompt you will see asks where to save the key. However, there areactually two files that will be generated: the public key and the privatekey.

This prompt refers to the private key and whatever you enter will alsogenerate a second file for the public key that has the same name and .pubappended.

If you already have a key, you should specify a new filename. I use manySSH keys so I typically name them 'test-deploy', 'prod-deploy', 'ci-server'along with a unique project name. Naming is one of those hard computerscience problems, so take some time to come up with a system that works foryou and the development team you work with!

Next you will see a prompt for an optional passphrase:

Whether or not you want a passphrase depends on how you will use the key.The system will ask you for the passphrase whenever you use the SSH keyso it is more secure.However, if you are automating deployments with acontinuous integration server likeJenkins then you will not want a passphrase.

Be aware that it is impossible to recover a passphrase if it is lost. Keepthat passphrase safe and secure because otherwise a completely new key wouldhave to be generated.

Enter the passphrase (or just press enter to not have a passphrase) twice.You'll see some output like the following:

Your SSH key is now generated and ready to use!

What now?

Now that you have your public and private keys, I recommend settingup a Python development environment withone of the following tutorials so you can start coding:

Additional ssh-keygen command resources:

Questions? Contact me via Twitter@fullstackpythonor @mattmakai. I'm also on GitHub withthe username mattmakai.

See something wrong in this post? Forkthis page's source on GitHuband submit a pull request.

Introduction

Secure Shell (SSH) is an encrypted protocol used by Linux users to connect to their remote servers.

Generally, there are two ways for clients to access their servers – using password based authentication or public key based authentication.

Using SSH keys for authentication is highly recommended, as a safer alternative to passwords.

This tutorial will guide you through the steps on how to generate and set up SSH keys on CentOS 7. We also cover connecting to a remote server using the keys and disabling password authentication.

1. Check for Existing Keys

Prior to any installation, it is wise to check whether there are any existing keys on the client machines.

Open the terminal and list all public keys stored with the following command:

The output informs you about any generated keys currently on the system. If there aren’t any, the message tells you it cannot access /.ssh/id_*.pub , as there is no such file or directory.

2. Verify SSH is Installed

To check if thw package is installed, run the command:

If you already have SSH, the output tells you which version it is running. Currently, the latest version is OpenSSH 8.0/8.0p1.

Note: Refer to our guide If you need to install and enable SSH on your CentOS system.

Steps to Creating SSH keys on CentOS

1. Start by logging into the source machine (local server) and creating a 2048-bit RSA key pair using the command:

If you want to tighten up security measures, you can create a 4096-bit key by adding the -b 4096 flag:

2. After entering the command, you should see the following prompt:

3. To save the file in the suggested directory, press Enter. Alternatively, you can specify another location.

Note: If you already have a key pair in the proposed location, it is advisable to pick another directory. Otherwise it will overwrite existing SSH keys.

4. Next, the prompt will continue with:

Although creating a passphrase isn’t mandatory, it is highly advisable.

5. Finally, the output will end by specifying the following information:

Now you need to add the public key to the remote CentOS server.

You can copy the public SSH key on the remote server using several different methods:

1. using the ssh-copy-id script
2. using Secure Copy (scp)
3. manually copying the key

The fastest and easiest method is by utilizing ssh-copy-id. If the option is available, we recommend using it. Otherwise, try any of the other two noted.

1. Start by typing the following command, specifying the SSH user account, and the IP address of the remote host:

If it is the first time your local computer is accessing this specific remote server you will receive the following output:

2. Confirm the connection – type yes and hit Enter.

3. Once it locates the id_rsa.pub key created on the local machine, it will ask you to provide the password for the remote account. Type in the password and hit Enter.

4. Once the connection has been established, it adds the public key on the remote server. This is done by copying the ~/.ssh/id_rsa.pub file to the remote server’s ~/.ssh directory. You can locate it under the name authorized_keys.

5. Lastly, the output tells you the number of keys added, along with clear instructions on what to do next:

1. First, set up an SSH connection with the remote user:

2. Next, create the ~/.ssh directory as well as the authorized_keys file:

3. Use the chmod command to change the file permission:

chmod 700 makes the file executable, while chmod 600 allows the user to read and write the file.

4. Generate a ssh key on mac for github. Now, open a new terminal session, on the local computer.

5. Copy the content from id_rsa.pub (the SSH public key) to the previously created authorized_keys file on the remote CentOS server by typing the command:

With this, the public key has been safely stored on the remote account.

1. To manually add the public SSH key to the remote machine, you first need to open the content from the ~/.ssh/id_rsa.pub file:

2. As in the image below, the key starts with ssh-rsa and ends with the username of the local computer and hostname of the remote machine:

3. Copy the content of the file, as you will need later.

4. Then, in the terminal window, connect to the remote server on which you wish to copy the public key. Use the following command to establish the connection:

5. Create a ~/.ssh directory and authorized_keys file on the CentOS server with the following command:

6. Change their file permission by typing:

7. Next, open the authorized_keys file with an editor of your preference. For example, to open it with Nano, type:

8. Add the public key, previously copied in step 2 of this section, in a new line in (under the existing content).

9. Save the changes and close the file.

10. Finally, log into the server to verify that everything is set up correctly.

Once you have completed the previous steps (creating an RSA Key Pair and copying the Public Key to the CentOS server), you will be able to connect to the remote host without typing the password for the remote account.

All you need to do is type in the following command:

If you didn’t specify a passphrase while creating the SSH key pair, you will automatically log in the remote server.

Otherwise, type in the passphrase you supplied in the initial steps and press Enter.

Once the shell confirms the key match, it will open a new session for direct communication with the server.

Although you managed to access the CentOS server without having to provide a password, it still has a password-based authentication system running on the machine. This makes it a potential target for brute force attacks.

You should disable password authentication entirely by following the outlined steps.

Note: Consider performing the following steps through a non-root account with sudo privileges, as an additional safety layer.

1. Using the SSH keys, log into the remote CentOS server which has administrative privileges:

2. Next, open the SSH daemon configuration file using a text editor of your choice:

3. Look for the following line in the file:

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4. Edit the configuration by changing the yes value to no. Thus, the directive should be as following:

5. Save the file and exit the text editor.
6. To enable the changes, restart the sshdservice using the command:

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7. Verify the SSH connection to the server is still functioning correctly. Open a new terminal window and type in the command:

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In this article, you learned how to generate SSH key pairs and set up an SSH key-based authentication. We also covered copying keys to your remote CentOS server, and disabling SSH password authentication.

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