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- All right, our next topic is about SSH.

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SSH is secure shell.

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Why would you want to use secure shell?

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Well, for the simple reason

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that it provides a remote shell access.

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The thing is that many
people are working with Linux

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but they are working with Linux in cloud

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or as a virtual machine.

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And if that's the case

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you have no direct access
to your Linux machine.

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That is why you need secure shell.

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In order to use secure shell

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you need to install it
and you need to enable it.

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If you're on Ubuntu,

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sudo apt install openssh-server.

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And if you're on Red Hat,

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well by default on Red Hat,

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you will find that ssh is
normally already installed.

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If that is not the case,

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sudo dnf install openssh-server

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followed by sudo systemctl enable.

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The (indistinct) is now sshd.

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Next,

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you need an SSH client
to access the SSH server.

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If you're on Linux and MacOS,

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a native command line
SSH client is available.

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If you're on Windows
you can use MobaXterm.

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MobaXterm is an easy
to use Windows utility

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in which you enter the IP
address of your target machine

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and you can easily connect to
your target machine using SSH.

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Now, SCP is a convenient tool
that allows you to copy files

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from the local computer
to the remote computer.

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And why am I mentioning it here?

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For the simple reason that SCP
is a part of the SSH package.

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So you install SSH,

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you get SCP for free.

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So the command looks like scp/etc/hosts

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to 192.168.29.111:/tmp/.

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And you can see that the 192.168.29.111,

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that's the name of the server.

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And the name of the server
has a colon behind it

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and after that, there's the path.

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Now let me demonstrate how
we can get started with SSH.

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So for this demo I'm starting on Ubuntu,

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using sudo apt install openssh-server.

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Because on Ubuntu you
don't get SSH by default.

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Well, depends on Ubuntu server.

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There's an option that is asking you,

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hey, do you want to install OpenSSH?

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And if you answer yes, you get it,

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but otherwise you don't.

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Now I'm going to use ip a.

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Ip a, one of the first
commands that we learned about,

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is showing me that this Ubuntu machine

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is 192.168.29.142.

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That's the IP address
that I'm going to use.

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So let me go to the CentOS machine.

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And from the CentOS machine

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I'm using ssh student@192.168.29.141.

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And there we go.

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This is what's happening the first time

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that you make connection
with the remote SSH server.

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It's probably complaining
about some key fingerprint.

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What is that?

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That's the identity.

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The SSH client is keeping
the identity of the host

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that it has connected with in the past.

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That's an additional level of security.

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So if you answer yes,

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you store the identity locally,

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and the next time that you
log in to this remote server

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you will not be prompted anymore.

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Your local client knows that
you are on the right server.

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And oops, do you see that?

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I opened an SSH session to myself.

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That's not what I wanted.

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I wanted to go to Ubuntu, 142.

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Aha, let's try it again, 142.

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Again, the prompt for the identity,

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I'm entering my student password,

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and look at that, welcome to Ubuntu.

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I'm on Ubuntu and I
can do whatever I want.

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Well, you know what I want?

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I want to create a file,

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echo greetings from ubuntu

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to ubunut.txt.

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What is ubunut?

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That's just a file name.

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And I'm going to use scp of ubunut.txt

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to 192.168.29.141:/tmp/.

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That's the SCP command,

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and SCP is pretty convenient as well.

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So I'm entering yes because
I want to copy it over.

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And there we go,

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I'm copying it over using
the student account.

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Now you can also copy it over
using another user account.

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In SSH you can always use username@.

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Username@ in front of
the name of your server

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will connect as that specific user.

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Now it happens to be that on
CentOS there's the root user.

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So I am being prompted for
the root user password here,

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and that is copying ubunut to
the root user home directory.

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So if I use sudo cat /root/ubunut.txt,

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then you can see greetings from ubuntu.

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And hey, did you notice?

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I wasn't prompted for any sudo password.

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So it seems that my sudo cat
is working the way I wanted it.

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That's all for now.