How to ssh to a a Linux VM

What Is SSH?

One essential tool to master as a system administrator is SSH.

SSH, or Secure Shell, is a protocol used to securely log onto remote systems. It is the most common way to access remote Linux and Unix-like servers, such as VPS instances.

In this guide, we will discuss how to use SSH to connect to a remote system.

Basic Syntax
The tool on Linux for connecting to a remote system using SSH is called, unsurprisingly, ssh.

The most basic form of the command is:

ssh remote_host

The remote_host in this example is the IP address or domain name that you are trying to connect to.

This command assumes that your username on the remote system is the same as your username on your local system.

If your username is different on the remote system, you can specify it by using this syntax:
ssh remote_username@remote_host

Once you have connected to the server, you will probably be asked to verify your identity by providing a password.

Later, we will cover how to generate keys to use instead of passwords.

To exit back into your local session, simply type:

How Does SSH Work?

SSH works by connecting a client program to an ssh server.

In the above commands, ssh is the client program. The ssh server is already running on the remote_hostthat we specified.

You will be presented with a login screen:



Log in with your credentials.

The process needed to start an ssh server depends on the distribution of Linux that you are using.

On Ubuntu, you can start the ssh server on the VPS by typing:

sudo service ssh start

That should start the sshd server and you can then log in remotely.

How To Configure SSH

When you change the configuration of SSH, you are changing the settings of the sshd server.

In Ubuntu, the main sshd configuration file is located at /etc/ssh/sshd_config.

Back up the current version of this file before editing:

sudo cp /etc/ssh/sshd_config{,.bak}

Open it with a text editor:

sudo nano /etc/ssh/sshd_config

You will want to leave most of the options in this file alone. However, there are a few you may want to take a look at:

Port 22

The port declaration specifies which port the sshd server will listen on for connections. By default, this is 22.

It may be a good idea to change this to a non-standard port to help obscure your server from random port scans. If you do change your port, we will show you how to connect to the new port later on.

HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_dsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key

The host keys declarations specify where to look for global host keys. We will discuss what a host key is later.

SyslogFacility AUTH
LogLevel INFO

These two items indicate the level of logging that should occur.

If you are having difficulties with SSH, increasing the amount of logging may be a good way to discover what the issue is.

LoginGraceTime 120
PermitRootLogin yes
StrictModes yes

These parameters specify some of the login information.

LoginGraceTime specifies how many seconds to keep the connection alive without successfully logging in.

It may be a good idea to set this time just a little bit higher than the amount of time it takes you to log in normally.

PermitRootLogin selects whether root is allowed to log in.

In most cases, this should be changed to “no” when you have created user account that has access to elevated privileges (through su or sudo) and can log in through ssh.

strictModes is a safety guard that will refuse a login attempt if the authentication files are readable by everyone.

This prevents login attempts when the configuration files are not secure.

X11Forwarding yes
X11DisplayOffset 10

These parameters configure an ability called X11 Forwarding. This allows you to view a remote system’s graphical user interface (GUI) on the local system.

This option must be enabled on the server and given with the client during connection with the “-X” option.

If you changed any settings in this file, make sure you restart your sshd server to implement your modifications:

sudo service ssh restart

You should thoroughly test your changes to ensure that they operate in the way you expect.

It may be a good idea to have a few sessions active when you are making changes. This will allow you to revert the configuration if necessary.

If you run into problems, remember that you can log in through the Console Access button on your droplet page.

How To Log Into SSH with Keys

While it is helpful to be able to log in to a remote system using passwords, it’s often a better idea to set up key-based authentication.

How Does Key-based Authentication Work?

Key-based authentication works by creating a pair of keys: a private key and a public key.

The private key is located on the client machine and is secured and kept secret.

The public key can be given to anyone or placed on any server you wish to access.

When you attempt to connect using a key-pair, the server will use the public key to create a message for the client computer that can only be read with the private key.

The client computer then sends the appropriate response back to the server and the server will know that the client is legitimate.

This entire process is done in the background automatically after you set up keys.

How To Create SSH Keys

SSH keys should be generated on the computer you wish to log in from. This is usually your local computer.

Enter the following into the command line:

ssh-keygen -t rsa

Press enter to accept the defaults. Your keys will be created at ~/.ssh/ and ~/.ssh/id_rsa.

Change into the .ssh directory by typing:

cd ~/.ssh

Look at the permissions of the files:

ls -l
-rw-r--r-- 1 demo demo  807 Sep  9 22:15 authorized_keys
-rw------- 1 demo demo 1679 Sep  9 23:13 id_rsa
-rw-r--r-- 1 demo demo  396 Sep  9 23:13

As you can see, the id_rsa file is readable and writable only to the owner. This is how it should be to keep it secret.

The file, however, can be shared and has permissions appropriate for this activity.

How To Transfer Your Public Key to the Server

You can copy the public key to the remote server by issuing this command:

ssh-copy-id remote_host

This will start an SSH session, which you will need to authenticate with your password.

After you enter your password, it will copy your public key to the server’s authorized keys file, which will allow you to log in without the password next time.

Client-Side Options

There are a number of optional flags that you can select when connecting through SSH.

Some of these may be necessary to match the settings in the remote host’s sshd file.

For instance, you if you changed the port number in your sshd configuration, you will need to match that port on the client-side by typing:

ssh -p port_number remote_host

If you only wish to execute a single command on a remote system, you can specify it after the host like so:

ssh remote_host command_to_run

You will connect to the remote machine, authenticate, and the command will be executed.

As we said before, if X11 forwarding is enabled on both computers, you can access that functionality by typing:

ssh -X remote_host

Providing you have the appropriate tools on your computer, GUI programs that you use on the remote system will now open their window on your local system.


Learning your way around SSH is a worthwhile pursuit, if only because it is such a common activity.

As you utilize the various options, you will discover more advanced functionality that can make your life easier. SSH has remained popular because it is secure, light-weight, and useful in diverse situations.

Zimbra Mail settings for outlook

This is a guide on how to setup Zimbra mailbox on outlook

Incoming mail settings or mail.domain e.g

Leave the ports to the default ones allocated by outlook


Outgoing mail settings or mail.domain e.g

Leave the ports to the default ones allocated by outlook

Remote Desktop To A Windows Server

Remote Desktop To A Windows Server

Learn how to connect to your Windows Server using Remote Desktop.

You will need to Find Your Server Information Details before logging on to your server via Remote Desktop.

Step 1
If your home or work computer (where ever you may be) is a Windows Operating System, the Remote Desktop application will already be installed.

Windows XP:

Click Start > All Programs > Accessories > Remote Desktop Connection or
Start > All Programs > Accessories > Communications > Remote Desktop Connection Launch Remote Desktop Connection from the Start menu

Launch Remote Desktop Connection from the Start menu

If you can not find the Remote Desktop Connection icon, keep looking in the Accessories sub-menus. The icon may be in a non-standard location.

Windows Vista/Windows 7:
Click the Start Menu Button and in the Search Box, type Remote Desktop and the icon should appear. Click the icon to launch.
Launch Remote Desktop Connection from the Start Menu

Launch Remote Desktop Connection from the Start Menu
Step 2
In the Remote Desktop window, type your IP address of your server or a domain that points to the server and click the Connect button.
Enter the server's IP address and click Connect

Enter the server’s IP address and click Connect
Step 3
If you are prompted by a Security Warning, click the Connect button.
Click the Connect button

Click the Connect button
Step 4
If using Windows Vista or Windows 7, you may have to select Use another account.
Select Use another account

Select Use another account
Step 5
By default, you will use the User Name and Password listed in the 1&1 Control Panel in the Server Access Data section. Enter the username and password and then click the OK button to connect.
Enter your credentials to log in

Enter your credentials to log in