A beginner’s guide to SSH for remote connection on Linux

Establish connections with remote computers using secure shell.
139 readers like this.
woman on laptop sitting at the window

CC BY 3.0 US Mapbox Uncharted ERG

One of Linux's most appealing features is the ability to skillfully use a computer with nothing but commands entered into the keyboard—and better yet, to be able to do that on computers anywhere in the world. Thanks to OpenSSH, POSIX users can open a secure shell on any computer they have permission to access and use it from a remote location. It's a daily task for many Linux users, but it can be confusing for someone who has yet to try it. This article explains how to configure two computers for secure shell (SSH) connections, and how to securely connect from one to the other without a password.


When discussing more than one computer, it can be confusing to identify one from the other. The IT community has well-established terms to help clarify descriptions of the process of networking computers together.

  • Service: A service is software that runs in the background so it can be used by computers other than the one it's installed on. For instance, a web server hosts a web-sharing service. The term implies (but does not insist) that it's software without a graphical interface.
  • Host: A host is any computer. In IT, computers are called a host because technically any computer can host an application that's useful to some other computer. You might not think of your laptop as a "host," but you're likely running some service that's useful to you, your mobile, or some other computer.
  • Local: The local computer is the one you or some software is using. Every computer refers to itself as localhost, for example.
  • Remote: A remote computer is one you're not physically in front of nor physically using. It's a computer in a remote location.

Now that the terminology is settled, you can begin.

Activate SSH on each host

For two computers to be connected over SSH, each host must have SSH installed. SSH has two components: the command you use on your local machine to start a connection, and a server to accept incoming connection requests. Some computers come with one or both parts of SSH already installed. The commands vary, depending on your system, to verify whether you have both the command and the server installed, so the easiest method is to look for the relevant configuration files:

$ file /etc/ssh/ssh_config
/etc/ssh/ssh_config: ASCII text

Should this return a No such file or directory error, then you don't have the SSH command installed.

Do a similar check for the SSH service (note the d in the filename):

$ file /etc/ssh/sshd_config
/etc/ssh/sshd_config: ASCII text

Install one or the other, as needed:

$ sudo dnf install openssh-clients openssh-server

On the remote computer, enable the SSH service with systemd:

$ sudo systemctl enable --now sshd

Alternately, you can enable the SSH service from within System Settings on GNOME or System Preferences on macOS. On the GNOME desktop, it's located in the Sharing panel:

Start a secure shell

Now that you've installed and enabled SSH on the remote computer, you can try logging in with a password as a test. To access the remote computer, you must have a user account and a password.

Your remote user doesn't have to be the same as your local user. You can log in as any user on the remote machine as long as you have that user's password. For instance, I'm sethkenlon on my work computer, but I'm seth on my personal computer. If I'm on my personal computer (making it my current local machine) and I want to SSH into my work computer, I can do that by identifying myself as sethkenlon and using my work password.

To SSH into the remote computer, you must know its internet protocol (IP) address or its resolvable hostname. To find the remote machine's IP address, use the ip command (on the remote computer):

$ ip addr show | grep "inet "
inet scope host lo
inet brd [...]

If the remote computer doesn't have the ip command, try ifconfig instead (or even ipconfig on Windows).

The address is a special one and is, in fact, the address of localhost. It's a "loopback" address, which your system uses to reach itself. That's not useful when logging into a remote machine, so in this example, the remote computer's correct IP address is In real life, I would know that because my local network uses the subnet. If the remote computer is on a different network, then the IP address could be nearly anything (never, though), and some special routing is probably necessary to reach it through various firewalls. Assume your remote computer is on the same network, but if you're interested in reaching computers more remote than your own network, read my article about opening ports in your firewall.

If you can ping the remote machine by its IP address or its hostname, and have a login account on it, then you can SSH into it:

$ ping -c1
PING ( 56(84) bytes of data.
64 bytes from icmp_seq=1 ttl=64 time=4.66 ms
$ ping -c1 akiton.local
PING ( 56(84) bytes of data.

That's a success. Now use SSH to log in:

$ whoami
$ ssh sethkenlon@
bash$ whoami

The test login works, so now you're ready to activate passwordless login.

Create an SSH key

To log in securely to another computer without a password, you must have an SSH key. You may already have an SSH key, but it doesn't hurt to create a new one. An SSH key begins its life on your local machine. It consists of two components: a private key, which you never share with anyone or anything, and a public one, which you copy onto any remote machine you want to have passwordless access to.

Some people create one SSH key and use it for everything from remote logins to GitLab authentication. However, I use different keys for different groups of tasks. For instance, I use one key at home to authenticate to local machines, a different key to authenticate to web servers I maintain, a separate one for Git hosts, another for Git repositories I host, and so on. In this example, I'll create a unique key to use on computers within my local area network.

To create a new SSH key, use the ssh-keygen command:

$ ssh-keygen -t ed25519 -f ~/.ssh/lan

The -t option stands for type and ensures that the encryption used for the key is higher than the default. The -f option stands for file and sets the key's file name and location. You'll be prompted to create a password for your SSH key. You should create a password for the key. This means you'll have to enter a password when using the key, but that password remains local and isn't transmitted across the network. After running this command, you're left with an SSH private key called lan and an SSH public key called lan.pub.

To get the public key over to your remote machine, use the ssh-copy-id. For this to work, you must verify that you have SSH access to the remote machine. If you can't log into the remote host with a password, you can't set up passwordless login either:

$ ssh-copy-id -i ~/.ssh/lan.pub sethkenlon@

During this process, you'll be prompted for your login password on the remote host.

Upon success, try logging in again, but this time using the -i option to point the SSH command to the appropriate key (lan, in this example):

$ ssh -i ~/.ssh/lan sethkenlon@
bash$ whoami

Repeat this process for all computers on your network, and you'll be able to wander through each host without ever thinking about passwords again. In fact, once you have passwordless authentication set up, you can edit the /etc/ssh/sshd_config file to disallow password authentication. This prevents anyone from using SSH to authenticate to a computer unless they have your private key. To do this, open /etc/ssh/sshd_config in a text editor with sudo permissions and search for the string PasswordAuthentication. Change the default line to this:

PasswordAuthentication no

Save it and restart the SSH server (or just reboot):

$ sudo systemctl restart sshd && echo "OK"

Using SSH every day

OpenSSH changes your view of computing. No longer are you bound to just the computer in front of you. With SSH, you have access to any computer in your house, or servers you have accounts on, and even mobile and Internet of Things devices. Unlocking the power of SSH also unlocks the power of the Linux terminal. If you're not using SSH every day, start now. Get comfortable with it, collect some keys, live more securely, and expand your world.

What to read next
Seth Kenlon
Seth Kenlon is a UNIX geek, free culture advocate, independent multimedia artist, and D&D nerd. He has worked in the film and computing industry, often at the same time.


It's also worth looking at your ssh log files once you open any computer to remote ssh. You will see constant attempts to log into the system.

Great article, appreciate your hard work! This is good advice too, so many systems get compromised because of a weak password.

it didn't work.I've the following environment for studing: ubuntu server which has been accessed by my client (fedora). I was able to create the priv key and the public one on the server side (ubuntu server) then I ran:

ssh-copy-id -i ~/.ssh/lan.pub my_user@My_Server

Does it must run on the server side or on my client machine?

When you use ssh-copy-id, you use it from the machine you want to SSH *from* (this is considered your "local" machine). In the scenario you describe, that means you'll run it from your Fedora machine. It sounds like you did that (I assume your server is My_Server), so it should work. I'd need to know more about what error you've encountered.

The comment section isn't the greatest format for support, though. I suggest going over to http://linuxquestions.org, signing up for an account (it's $0), and asking for help there. Lots of people eager to help.

In reply to by Rafael da Silv… (not verified)

You should always protect your private key with a passphrase. We had to disable SSH key access to our HPC system because users didn't use a passphrase with their key.

Great point. I've updated the article to reinforce the importance of a passphrase on the key itself.

In reply to by jonathan

Here's another *really* useful hint:

ssh -Y sethkenlon@

Then you can run any X-based program from the remote machine, and the windows show up on your local machine.

So I log in to my Raspberry Pi and run

$ pcmanfm

and this runs the file browser, with the windows on my local machine!

just some improving remark:

Instead of specifying the sshkey in the commandline, you can use ssh-agent:
First associate the key just once with the agent

eval `ssh-agent`

then you can use

ssh-copy-id remotelogin@remotehost

to copy all the keys registered in the ssh-agent to the remotehost.

next time ssh will try automaticly to use the key associated with the ssh-agent

Great workflow. I like to teach the manual way first so it feels less "magical" (plus I use -i a lot because I have unique keys for different hosts). But I like your method, too. Maybe it's material for an add-on article!

In reply to by Joost Ringoot (not verified)

Creative Commons LicenseThis work is licensed under a Creative Commons Attribution-Share Alike 4.0 International License.