Introduction

When establishing a remote connection between a client and a server, a primary concern is ensuring security. For Linux users, the best practice of accessing and managing your server remotely is through the cryptographic protocol known as Secure Shell (SSH).

Generate SSH Keys on Windows 10 Use the Ubuntu command line or PuTTY running on Windows 10 to generate SSH keys for use with SSH authentication and your own remote connections. Difficulty: 2 out of 5. In this guide, I will explain to you how to set up SSH keys on Ubuntu 18.04. SSH is an acronym for Secure Shell. Secure Shell (SSH is a cryptographic network protocol, and it is responsible for encrypting the information between a user and the remote machine. It allows users to perform secure network services.

SSH encrypts all data transferred from one machine to another, making sure that no sensitive information is compromised during the process. As a desktop client, you can safely run a command line, transfer files, secure network services, and much more.

By following the steps below, you will learn how to enable SSH on Ubuntu 18.04.

• Ubuntu 18.04 Bionic Beaver (or any other Debian-based Linux, including Ubuntu 17.04, 16.10, 16.04, etc.)
• A user with sudo privileges
• Permissions to access the remote computer
• Access to a terminal/command-line
• The apt-get tool, pre-loaded in Ubuntu and other Debian-based distros
• OpenSSH 7.5 or higher

The SSH server is not installed by default on Ubuntu systems. To install and enable SSH on Ubuntu follow the steps found below:

Matlab r2015b activation key generator. 1. Open the terminal either by using the CTRL+ALT+T keyboard shortcut or by running a search in Ubuntu Dash and selecting the Terminal Icon.

2. Before starting the installation process, check if an SSH server has already been installed on your computer. Use the following command:

If you see the following message, you will have to go through the SSH installation process.

3. To install SSH, first update the package repository cache with:

4. Now install the OpenSSH software package by entering:

If prompted, type in your password and press y(yes) to permit the installation.

5. To verify the installation was successful and SSH is running use the command:

The confirmation message that you are looking for is: Active: active (running)

This means you have installed and enabled SSH on your remote machine, which can now accept commands from your SSH client.

6. To return to the command line prompt enter q.

Once you have gone through the process of enabling SSH on Ubuntu 18.04, you are ready to log into your remote machine.

1. Open the terminal (CTRL+ALT+T) and type the following command:

Change the username and IP address to the username and IP address of the Ubuntu computer on which you have installed SSH.

Generate Ssh Keys Ubuntu 18.04 Update

2. If you do not know the IP address, you can quickly identify it through the terminal by typing the command:

This should display the public IP address of the machine where SSH was installed.

Once you have identified and typed in all the information, you have officially logged into your server. You are free to manage it from the comfort of your workstation safely.

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After successfully installing OpenSSH on Ubuntu, you can edit its configuration file.

You can change the default port (generally a good idea, as a precautionary security measure), disable the “root ” user or make other configuration adjustments.

1. Open your SSH configuration file with the command:

Gedit is a text editor which comes by default in Ubuntu, but you can also use other text editors such as nano. If you prefer using nano, you can easily install it by running the following command:

2. When prompted, type in your password and press y(yes) to permit the installation.)

3. Then replace “gedit ” with “nano” type in the command:

4. Now that you have opened the file (using any of the text editors recommended above) find and make any necessary changes.

For example, if you wish to change the port number to listen on TCP port 2222 instead of the default TCP port 22, find the line in which Port 22 is specified by default, and change it to Port 2222.

Important: Changing the default port number is an SSH security best practice. Everyone is aware of the default port number so changing it is a recommended security precaution.

Another critical security precaution is to make sure that the root is disabled. That way, the root user cannot be invoked remotely, and security will be significantly improved.

1. In the configuration file, find the line that reads PermitRootLogin_yesand change it to PermitRootLogin_no.

2. After you have made the desired changes, save and close the file by using the CTRL+W keyboard shortcut (or the commands to save and close in your editor of choice).

3. For the changes to take into effect, restart SSH with the following command:

If you have decided to change the default port number, you must configure your firewall to allow traffic via the specified port.

Let’s use the example of Port 2222.

The default firewall configurations tool in Ubuntu is UFW, configure it with the command:

Some firewalls may require allowing traffic to the public IP address of the machine running SSH.

Note: The 'p2222” is the port number we have defined in the Configure SSH section. If you used the default port 22, then it is not necessary to put the port number.

How to Disable SSH on Ubuntu

To temporarily disable SSH:

To start SSH again:

To completely disable SSH after reboot:

To enable SSH on Ubuntu host again:

By following the simple steps above, you now know how to enable SSH on Ubuntu 18.04. Now you can establish a reliable and secure protocol between you and a remote device.

Get started by logging to your machine to perform sysadmin tasks with the command prompt.

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SSH (Secure Shell) is a encrypted protocol which allows client system to communicate securely with a server. You can connect to your system remotely, perform administrative tasks and access files. Communicate with server using SSH keys is more secure and convenient way than password authentication. In this tutorial, we have described how to create SSH keys on Ubuntu 18.04 system and how to copy it to server using different ways.

Prerequisites

Before you begin, you should have the non-root user account on your server with sudo privileges.

Creating SSH keys on Ubuntu

At first, we will create a key pair on client system using below command:

By default, ssh-keygen will generate 2048-bit RSA key pair. If you wish to create larger 4096-bit key then you can pass -b 4096 in flag as below:

It should show output like below:

Hit the Enter key to save the key pairs at ./ssh directory or you can specify location as per your choice.

After that, it will prompt to enter a secure passphrase as below. Passphrase will add an additional security layer to your keys. It is optional, if you don’t want to set then you can skip it by just hitting Enter key.

Next, you will see output as following:

Now you have public and private keys which you can use to authenticate with your Ubuntu server.

You also can verify that your files are generated or not by typing:

It will show output like this:

Copy the Public Key to Ubuntu Server

Now, next step is to place public key to your Ubuntu 18.04 server. Simple and fast way to copy public is to use ssh-copy-id utility. Run the below command:

It will be prompted to enter password for your username:

Once the user is authenticate successfully, the public key will be appended to ~/.ssh/authorized_keys file on remote user and connection will be disconnected.

Now you can try login to your machine with command ssh username@server_ip_address and check that only the key(s) added which you want to add.

If your local system don’t have ssh-copy-id utility installed then you can use following command to copy the public key:

Ensure that you have password-based SSH access to your server then only you can use above method.

Login to the Server using SSH Keys

Now, you should be able to login to the remote machine without the remote user’s password.

You can try to connect using SSH command:

If you are first time to login then it may prompt you as following. Type yes and hit Enter key to continue:

Now, if you haven’t set passphrase for your keys then you will be logged in immediately without asking passphrase. Otherwise it will be asked to enter passphrase. After successful authentication, a new shell session will open your user account on the Ubuntu 18.04 server.

Disable SSH Password Authentication

You can add one more security layer by disabling the password authentication for SSH. Before starting process, make sure that you are able to authenticate to your server without entering password and must have sudo enabled user account.

Let’s login to your server using ssh:

Generate Ssh Keys Ubuntu 18.04 Windows 7

Now edit the SSH configuration file located at /etc/ssh/sshd_config:

Find PasswordAuthentication directive and if line commented out then uncomment the line and set the value to “no” as given below:

Save and close the file. You must need to restart the SSH service using below command:

Now, password-based authentication is disabled on your Ubuntu server.

Ubuntu 18.04 Allow Ssh

Conclusion

You learned how to create a new SSH keys pair and set up an SSH key-based authentication on Ubuntu 18.04 machine. You can set up same key to multiple remote hosts. At the end, you also learned how to disable SSH password authentication.

By default, SSH listens on port 22. You can reduce the risk of automated attacks by changing the default SSH port.

If you have any question or suggestion, please leave comment below.