How To: Login To SSH To Run One Command

In today’s article, we’re going to learn how to login to SSH to run one command. Yes, it’s another SSH article! However, this one should be relatively short. I’ve covered SSH a great deal already. This is just one more SSH trick.

SSH stands for Secure Shell and is a way to remotely control other computers. As I said in the opening paragraph, I’ve already covered a lot of SSH articles, because SSH is a tool I use regularly and it’s a tool I really like.

SSH lets me manage computers on the other side of the country without even leaving my chair. I also use SSH to manage various computers around my house. If I need to do something on a computer in another room, I can just SSH into it and do what I needed to do. It’s great!

Well, today’s SSH article is a bit different. We’re going to login to SSH to run one command. That’s all we’re going to do. We’ll login, automatically run the command, and then automatically exit the SSH connection. This is useful if you want to run a script, update, etc…

There are some previous SSH articles that you might want to read:

Install SSH to Remotely Control Your Linux Computers
Prevent SSH Root Login
Show Failed SSH Login Attempts

Alternatively, you can click to search for SSH articles. I’ve covered quite a bit of SSH material, so you can learn quite a bit from those links – even if you’re already familiar with SSH.

Well then, let’s just jump into the article… It really shouldn’t take long.

Login To SSH To Run One Command:

Like oh so many articles, and this one involving SSH, you’re going to need to start off with a terminal. You’ll also need a device that has SSH properly setup and ready to run. You can actually set SSH up on the computer you’re using and just SSH into localhost to practice this.

And, of course, if you don’t know how to open your terminal, just press CTRL + ALT + T and your default terminal should open.

With your terminal now open, the format of the command is something like this:

For example, if I wanted to connect via SSH to run one command, and that command was to list the files in the home directory, the command would look like this:

Note: That device doesn’t face the public internet, so I don’t have SSH keys enabled on the device. So, that means I have to enter my password in the image below. With that in mind, the output of that command would look like this:

login to ssh to run one command
See? It logs into the remote device, runs one command, and exits! Pretty neat, huh?

Of course, you can make it your own and there would be one less step if you had set up SSH keys. You can also make it more complicated if you want. You could try any one of the following commands, adjusting it for your needs:

Go ahead and play around with this. If you want to login to SSH to run one command, that’s how you do it. You can make the command as simple or as complicated as you want. So long as you string it together properly, the sky’s the limit!

Like I said above, you can just install SSH on your single device and practice what you read in these SSH articles. It’s not particularly taxing. There are plenty of articles to help you along the way.

Closure:

See? It’s really not all that hard to login to SSH to run one command and then exit automatically after that command has been run. It’s another handy SSH trick that you can add to your SSH toolbox. Also, the article is longer than I anticipated. Ah well…

What comes next? I have no idea. I try to not write too many consecutive articles on the same subject. Mixing them up seems the best way to go about it, as the site’s meant to be searched and not read like a blog. I do have a bunch of SSH content, but I’ve also covered a whole lot of it already.

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Install SSH to Remotely Control Your Linux Computers

If this article’s headline looks vaguely familiar, it’s probably because I previously wrote an article that told you how to install SSH. That article was on the earlier site. This article will show you how to install SSH, so that you can remotely control your Linux computers.

The old site, while up, will redirect to this address. It’s also a bit of a misnomer. We’ll be installing ‘OpenSSH‘ and enabling SSH. SSH is the protocol, OpenSSH is the application, specifically the ‘openssh-server’.

Let’s say your computer is in another room, in another state, over in another country, or perhaps on another continent entirely. How are you going to manage it? Servers are scattered across the world and it is not even remotely economical to send a person to administer each one of them in person. You’ll need to manage these devices remotely.

One of the best tools for this job is SSH.

As a home-use note; SSH is perfectly suitable to manage my own router. It’s quick, easy, lightweight, effective, doesn’t require an attached monitor, and more. What’s not to like? I SSH into my computers all the time! In fact, right this minute I’m connected to two other computers via SSH!

SSH has been around since 1995 and it lets you issue commands on a remote computer. In fact, the man page describes it like this:

ssh — OpenSSH remote login client

Which, as you can guess, means it lets you login to remote computers so that you can control them. It’s a pretty handy tool to have in your toolbox and it’s actually simple to install.

Install SSH:

SSH is really the protocol, and you can do many things over it. OpenSSH is the application that we’ll really be installing. Once that’s installed, you can login to the computer remotely and manage it that way. I use it quite often.

My homemade router doesn’t have a keyboard attached. It doesn’t even have a monitor attached. It’s not like I can just easily walk over and deal with it. I just got a laptop that, and it’s only used to test Lubuntu. I don’t always want to have to go over to the device and physically use it to start the test.

There’s also my dedicated server in Las Vegas – and I live in Maine. It wouldn’t be practical to fly out to Vegas every few days to run updates on the server. It wouldn’t make financial sense to go out there every time the server needed to be rebooted!

Those are all situations where you can use SSH. It’s available in pretty much every default repository out there. I’m surprised more people don’t use it. To get started, you just open your terminal (press CTRL + ALT + T on your keyboard) and enter the following:

If you’re using a distro with apt:

If you’re using a distro with yum:

Simply adjust that for your distro. For example, in OpenSUSE you may have installed it during the OS installation process. If it wasn’t installed during the initial OS installation then it’s just called ‘openssh’ – if you want to install a few of the applications surrounding openssh. You can also do a ‘sudo zypper install openssh-server’ like the rest of us.

Anyhow, once you’ve installed it, you may not even need to start it. If you install it on Ubuntu, you can go right ahead and test it immediately. If your distro requires that you start it manually, you should do that.

Once you’re done, you can test it easily enough. Try this:

If that works, you’ve properly installed openssh-server and can now make use of SSH. You may also need to enable it in  your firewall. Chances are that your firewall knows what SSH is.

To connect to your device from a remote computer, you’d do:

You can use a specific username in that command, like demonstrated in the testing command just above this command. It’s not mandatory, but doing so will skip a step.

Closure:

You can expect a couple more SSH articles, as this is woefully incomplete. A lot more can be done with SSH, plus SSH should be properly secured. For most of you, behind a NATed router, you don’t really have to worry too much unless you enable port forwarding. If you’re making the port available to the world-wide-web, you’re definitely going to need to add some security. Otherwise, there are a few nifty things you can do once SSH is enabled. We’ll cover those in future articles.

You can also connect with your hostname – probably. In many instances, you’d do this (distro-dependent):

For example, to connect to my testing laptop, I use the following command:

Go ahead and play around with it. There’s a number of ways to help secure SSH and we’ll go over some of that in a future article. I’ve been maintaining the ‘article every two days’ thing for a while now. I see no reason to expect that to not continue.

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