2. What Needs To Be Done Before Starting The Ssh Service?

SSH has become the default method of accessing a remote Linux server these days.

SSH stands for Secure Shell and it'southward a powerful, efficient, and popular network protocol used to plant communication between two computers in a remote fashion. And let's non forget the secure function of its name; SSH encrypts all traffic to foreclose attacks like hijacking and eavesdropping while offering different authentication methods and a myriad of configuration options.

In this beginner's guide, you'll learn:

The basic concept of SSH
Setting up SSH server (on the arrangement y'all want to access remotely)
Connecting to remote server via SSH from the client machine (your personal computer)

The absolute basics of SSH

Before you see whatever configuration procedure, it will exist better to get through the absolute basic concept of SSH.

The SSH protocol is based on server-customer architecture. The "server" allows the "customer" to be connected over a advice channel. This aqueduct is encrypted and the exchange is governed by the employ of public and private SSH keys.

OpenSSH is one of the most pop open source tools that provides the SSH functionality on Linux, BSD and Windows.

For a successful SSH fix, y'all need to:

Have SSH server components on the motorcar that acts as the server. This is provided by openssh-server package.
Have SSH client component on the machine from where you want to connect to the remote server machine. This is provided by openssh-client bundle and virtually Linux and BSD distributions come up preinstalled with it.

It is important to keep a stardom between the server and client. Y'all might not want your personal computer to act as SSH server unless yous have good reasons where you lot want others to connect to your system via SSH.

Generally, you lot have a defended system working as the server. For case, a Raspberry Pi running Ubuntu server. You enable SSH on the Raspberry Pi then that you could control and manage the device from your chief personal computer using SSH in a terminal.

With that information, let's see how yous can prepare up a SSH server on Ubuntu.

Configuring SSH Server on Ubuntu

Setting up SSH is not complicated and only needs a few steps to practise information technology.

Prerequisites

A user with sudo privileges on the server machine
Internet connexion to download the required packages
At least another organization in your network. It can be some other figurer on your LAN, a remote server via Net, or a virtual machine hosted in your computer.

Again, the SSH server installation should be done on the system that you lot want to human action as server and to which you lot want to connect remotely via SSH.

Footstep 1: Install required packages

Permit'due south beginning by opening a terminal window to enter the necessary commands.

Call up to update your Ubuntu system before installing new packages or software with to make sure that you are running the latest versions.

                          sudo apt update && sudo apt upgrade

The package you need to run SSH Server is provided by openssh-server component from OpenSSH:

            sudo apt install openssh-server

Footstep 2: Checking the status of the server

Once the downloading and installation of the package is washed the SSH service should exist already running, but to exist sure we will bank check it with:

            service ssh status

You lot may also use the systemd commands:

            sudo systemctl status ssh

You should come across something like this, with the word Active highlighted. Striking q to return to the command prompt.

If in your case the service is non running you will have to activate like this:

            sudo systemctl enable --at present ssh

Step 3: Allowing SSH through the firewall

Ubuntu comes with a firewall utility called UFW (UncomplicatedFirewall) which is an interface for iptables that in plow manages the network'southward rules. If the firewall is agile, it may prevent the connection to your SSH Server.

To configure UFW and so that it allows the wanted admission, y'all need to run the post-obit command:

            sudo ufw permit ssh

The status of UFW can be checked running sudo ufw status.

At this time our SSH Server is up and running, just waiting for a connectedness from a client.

Connecting to the remote system from your local machine

Your local Linux system should already accept SSH client installed. If non, you may always install information technology using the following command on Ubuntu:

            sudo apt install openssh-client

To connect to your Ubuntu system y'all need to know the IP address of the computer and use the ssh command, like this:

            ssh [email protected]

Change username to your actual user in the organisation and address to the IP accost of your Ubuntu machine.

If you don't know the IP address of your computer you lot can type ip a in the final of the server and check the output. You should have something like this:

ssh find ip — Using "ip a" to observe the IP address

As tin can be seen here my IP address is 192.168.1.111. Let's try connecting using the [email protected] format.

            ssh [email protected]

The first time you lot connect to a SSH server, information technology will ask for permission to add the host. Type aye and hit Enter to continue.

Connecting for the first time with SSH — First fourth dimension connecting to the server

Immediately SSH tells you lot that the host was permanently added then asks for the password assigned to the username. Type in the password and hit Enter one more time.

Host added, at present type in the countersign

And voila! You will be logged into your Ubuntu organisation remotely!

Now you tin can work in your remote system's terminal as normal.

Endmost the SSH connexion

To shut the connectedness you lot just need to type exit and it will close information technology at once, without asking for confirmation.

Closing the connection with exit — Closing the connection with "exit"

Stopping and Disabling SSH in Ubuntu

If you want to stop SSH service y'all will need this command:

            sudo systemctl end ssh

This will terminate the service until you restart information technology or until the system is rebooted. To restart it, type:

            sudo systemctl showtime ssh

Now, if you want to disable it from starting during organisation boot, apply this:

            sudo systemctl disable ssh

This won't stop the service from running during the current session, merely from loading during startup. If you want to let it offset again during organization boot, type:

            sudo systemctl enable ssh

Other SSH clients

The tool ssh is included in most *nix systems, from Linux to macOS, just those are not the only options in existence, here are a couple of clients that can exist used from other operating systems:

PuTTY is a gratis and open source SSH customer which is hugely pop among Windows users. Y'all can also install PuTTY on Ubuntu. It's full of features and very easy to use. If you are connecting to your Ubuntu automobile from a Windows station, PuTTY is a groovy choice.
JuiceSSH is an amazing tool for Android users. If you are on the go and demand a mobile client to connect to your Ubuntu system, I amply recommend giving JuiceSSH a go. It's been around for almost 10 years and it's free to utilize.
And finally, Termius is bachelor for Linux, Windows, macOS, iOS, and Android. It has a gratuitous tier version and also several premium options. If you are running a lot of servers and working with teams sharing connections then Termius is a good selection for you lot.

Wrapping Upwardly

With these instructions, you tin set up SSH equally a server service in our Ubuntu systems to be able to connect remotely and deeply to your computer in order to work with the command line and perform whatsoever required task.

Our other website, Linux Handbook, has various advisory manufactures on SSH. From hither, I recommend reading the following:

Getting started with SSH on Linux
Using SSH Config file to manage multiple SSH connections
Adding public key to SSH server for password less authentication
SSH hardening tips to secure your SSH server

If yous find it overwhelming, Linux Handbook has a premium video form that explains SSH for beginners along with easily-on labs to follow. This volition requite you a more streamlined knowledge of the topic.

Happy remote working!