Dec 18, 2019 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 # Before generating a new SSH key pair first, check for existing SSH keys on your Ubuntu client machine. You can do that by running the following ls command: ls -l /.ssh/id.pub.
- Dec 18, 2019 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.
- Jan 24, 2020 A quick and practical introduction to creating SSH keys on Linux. In this tutorial, we’ll cover the basics of SSH keys and how to generate an SSH key pair in Linux. Secure Shell (SSH) Secure Shell (SSH) is a secure remote login protocol that leverages public-key cryptography to encrypt the communication between a client and a server.
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?
Resolution
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
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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:
3. Distribute the private key file to your new user.
Related Information
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Joel shows you how to manage user accounts on your Amazon EC2 Linux instance (5:47)
Introduction
Secure Shell (SSH) is an encrypted protocol used by Linux users to connect to their remote servers. Hibernate manytomany the join table has sequence generated primary key.
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
![Download Download](https://www.ssh.com/s/ssh-keygen-user-key-728x467-BMs00tMu.png)
Step 1: Create SSH Key Pair
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:
Generate New Ssh Key Linux
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:
- using the ssh-copy-id script
- using Secure Copy (scp)
- 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. 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.
Ssh Keys Download
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:
4. Edit the configuration by changing the
yes
value to no
. Thus, the directive should be as following:Create New Ssh Key Linux
5. Save the file and exit the text editor.
6. To enable the changes, restart the sshdservice using the command:
6. To enable the changes, restart the sshdservice using the command:
Generate New Ssh Keys Linux 10
7. Verify the SSH connection to the server is still functioning correctly. Open a new terminal window and type in the command:
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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