Centos Generate Ssh Key For User

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Set up your first SSH keys

Nov 02, 2018  We often use ssh-copy-id to copy ssh keys from our local Linux computers to RHEL servers in order to connect without typing in a password. This is not only for convenience; it enables you to script and automate tasks that involve remote machines. Also, using ssh keys. 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.

Use SSH keys for authentication when you are connecting to your server, or even between your servers. They can greatly simplify and increase the security of your login process. When keys are implemented correctly they provide a secure, fast, and easy way of accessing your cloud server.

Follow our guide and learn how to set up your first SSH keys for authentication using OpenSSH or PuTTYTray.

Preparing your server

To add an SSH key pair, first, create a hidden folder to your user account home directory on your cloud server with the following command.

Then restrict the permissions to that directory to just yourself with the command below.

This creates a secure location for you to save your SSH keys for authentication. However, note that since the keys are stored in your user home directory, every user that wishes to connect using SSH keys for authentication has to repeat these steps on their own profile.

Using OpenSSH to generate a key pair

Now continue on your own computer if you are using Linux or any other OS that has OpenSSH. PuTTY users should skip to the next section.

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1. Generate a new key pair in a terminal with the next command

The key generator will ask for location and file name to which the key is saved to. Enter a new name or use the default by pressing enter.

2. (Optional) Create a passphrase for the key when prompted

This is a simple password that will protect your private key should someone be able to get their hands on it. Enter the password you wish or continue without a password. Press enter twice. Note that some automation tools might not be able to unlock passphrase-protected private keys.


3. Copy the public half of the key pair to your cloud server using the following command

Replace the user and server with your username and the server address you wish to use the key authentication on.

This also assumes you saved the key pair using the default file name and location. If not, just replace the key path ~/.ssh/id_rsa.pub above with your own key name.

Enter your user account password for that SSH server when prompted.

You can now authenticate to your server with the key pair, but at the moment you would need to enter the passphrase every time you connect.

4. (Optional) Set up SSH Agent to store the keys to avoid having to re-enter passphrase at every login

Enter the following commands to start the agent and add the private SSH key.

Centos Generate Ssh Key For User List

Type in your key’s current passphrase when asked. If you saved the private key somewhere other than the default location and name, you’ll have to specify it when adding the key.

Afterwards, you can connect to your cloud server using the keys for authentication, and only having to unlock the key by repeating the last 2 steps once after every computer restart.

Using PuTTYTray to generate a key pair

If you are running Windows and PuTTYTray for SSH, you can use the built-in key generator from PuTTY to create a new key pair.

1. Click the Keygen button at the bottom of the PuTTY Configuration window to get started.

Then in the Key Generator window, check that the Type of key to generate at the bottom is set to SSH-2 RSA. The older SSH-1 was the first version on the standard but is now generally considered obsolete. Most modern servers and clients support SSH-2.

2. Click the Generate button to begin.

3. Keep moving your mouse over the blank area in any manner to help generate randomness for a few moments until the progress is complete.

With the keys finished, PuTTY will show the relative information about the pair along with the public key for easier copying.

4. (Optional) Enter a key passphrase in the 2 empty fields for the added security before continuing. The passphrase will protect your key from unauthorized use should someone be able to copy it. However, some automation tools might not be able to unlock passphrase-protected private keys.

5. Click the Save private key button and store it somewhere safe. Generally anywhere in your user directory is fine as long as your PC is password protected. Before closing the keygen, you may want to copy the public key to your clipboard, but you can always get it later as well.

Centos Generate Ssh Key For User Guide

Now that you have a new key saved on your computer, you’ll need to import it into the PuTTY key agent.

6. Click the Agent button to open the key manager in the PuTTY Configuration window.

7. Click Add Key button in the Key List, then browse to the location you saved the private key, select it and click Open.

Enter your key passphrase if asked.

This will import the key to your PuTTY client, but you still need to copy the public key over to your server.

8. Open an SSH connection to your cloud server and go to the SSH key directory.

9. Open or create the default file OpenSSH looks for public keys called authorized_keys.

10. Paste the public key into the file by simply right-clicking the SSH client window. Make sure the key goes on a single line for OpenSSH to be able to read it.

When you’ve copied the public key over to the authorized keys list, save the file and exit the editor. You can now test the public key authentication by logging in to your server again. You should not get asked for your password, but instead logged straight in with the key. If it’s not working, check that your private key is unlocked at your SSH Agent and try again.

Turn off password authentication

With SSH key authentication configured and tested, you can disable password authentication for SSH all together to prevent brute-forcing. When logged in to your cloud server.

1. Open the SSH configuration file with the following command.

2. Set the password authentication to no to disable clear text passwords.

3. Check that public key authentication is enabled, just to be safe and not get locked out from your server. If you do find yourself unable to log in with SSH, you can always use the Web terminal at your UpCloud control panel.

Then save and exit the editor.

4. Restart the SSH service to apply the changes by using the command below.

With that done your cloud server is now another step along towards security. Malicious attempts to connect to your server will results in authentication rejection, as plain passwords are not allowed, and brute-forcing an RSA key is practically impossible.



Remember to always keep your private keys safe. You can use the same key from multiple computers if you wish, or generate new ones on each client connecting to your cloud server for added security. Each user should generate their own key pair and passphrase for secure access control. With proper management, even in case one of the private keys gets compromised you won’t have to replace them all.

I want to add new user accounts that can connect to my Amazon Elastic Compute Cloud (Amazon EC2) Linux instance using SSH. How do I do that?

Short Description

Every Amazon EC2 Linux instance launches with a default system user account with administrative access to the instance. If multiple users require access to the instance, it's a security best practice to use separate accounts for each user.

You can expedite these steps by using cloud-init and user data. For more information, see How can I give a user permissions to connect to my EC2 Linux instance using SSH?


Create a key pair for the new user account

  • Create a key pair, or use an existing one, for the new user.
  • If you create your own key pair using the command line, follow the recommendations at create-key-pair or New-EC2KeyPair Cmdlet for key type and bit length.
  • If you create your own key pair using a third-party tool, be sure that your key matches the guidelines at Importing Your Own Public Key to Amazon EC2.

Add a new user to the EC2 Linux instance

1. Connect to your Linux instance using SSH.

2. Use the adduser command to add a new user account to an EC2 instance (replace new_user with the new account name). The following example creates an associated group, home directory, and an entry in the /etc/passwd file of the instance:

Note: If you add the new_user to an Ubuntu instance, include the --disabled-password option to avoid adding a password to the new account:

3. Change the security context to the new_user account so that folders and files you create have the correct permissions:

Note: When you run the sudo su - new_user command, the name at the top of the command shell prompt changes to reflect the new user account context of your shell session.

4. Create a .ssh directory in the new_user home directory:

5. Use the chmod command to change the .ssh directory's permissions to 700. Changing the permissions restricts access so that only the new_user can read, write, or open the .ssh directory.

6. Use the touch command to create the authorized_keys file in the .ssh directory:

7. Use the chmod command to change the .ssh/authorized_keys file permissions to 600. Changing the file permissions restricts read or write access to the new_user.

Retrieve the public key for your key pair

Retrieve the public key for your key pair using the method that applies to your configuration:

Verify your key pair's fingerprint

After you import your own public key or retrieve the public key for your key pair, follow the steps at Verifying Your Key Pair's Fingerprint.

Update and verify the new user account credentials

After you retrieve the public key, use the command shell session that is running under the context of the new user account to confirm that you have permission to add the public key to the .ssh/authorized_keys file for this account:

1. Run the Linux cat command in append mode:

2. Paste the public key into the .ssh/authorized_keys file and then press Enter.

Note: For most Linux command line interfaces, the Ctrl+Shift+V key combination pastes the contents of the clipboard into the command line window. For the PuTTY command line interface, right-click to paste the contents of the clipboard into the PuTTY command line window.

3. Press and hold Ctrl+d to exit cat and return to the command line session prompt.

(Optional) Allow the new user to use sudo

Note: If you don't want to allow the new user to use sudo, proceed to Verify that the new user can use SSH to connect to the EC2 instance.

1. Use the passwd command to create a password for the new user:

Note: You're prompted to reenter the password. Enter the password a second time to confirm it.

2. Add the new user to the correct group.

For Amazon Linux, Amazon Linux 2, RHEL, and CentOS:

Use the usermod command to add the user to the wheel group.

For Ubuntu:

Use the usermod command to add the user to the sudo group.

Verify that the new user can use SSH to connect to the EC2 instance

1. Verify that you can connect to your EC2 instance when using ssh as the new_user by running the following command from a command line prompt on your local computer:

To connect to your EC2 Linux instance using SSH from Windows, follow the steps at Connecting to Your Linux Instance from Windows Using PuTTY.

2. After you connect to your instance as the new_user by using SSH, run the id command from the EC2 instance command line to view the user and group information created for the new_user account:

The id command returns information similar to the following:

Centos Ssh Setup

3. Distribute the private key file to your new user.

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