====== Connecting to a Linux computer using SSH from a Linux computer (text mode interface) ======

Many software applications on Linux are designed in a way that they can be used using a text mode interface only. This means, there is no graphical user interface which is operated with a mouse or a touchscreen but just a command prompt which takes single text commands which can be combined with options and parameters.

To connect to a remote computer running Linux through SSH from a computer running Linux, first navigate through your //Applications// menu, find the //System Tools// submenu and click //Mate Terminal//.

{{:services:remote-access:ssh_terminal_menu.png|}}

The terminal window should open similar to the following picture. To establish an SSH connection to a remote Linux computer at the department, type:

ssh **username**@**computer**.physik.fu-berlin.de

It is highly recommended to use the computer //login// since it is a machine guaranteed to be running 24/7 and has enough hardware ressources to be used by several users simualtanously for login.

Thus:

**ssh username@login.physik.fu-berlin.de**

{{:services:remote-access:ssh_terminal_window2.png|}}

The SSH command has some additional, useful options:

  * -x - disable X forwarding
  * -X - enable X forwarding (allows to run remote graphical applications); use together with -C
  * -C - enable compression; use this when enabling X forwarding

=====Key authentication (required from outside the FU network)=====
Remote access using ssh from outside the FU network now requires **ssh-key** authentication.
Key authentication works by having files on each machine that act as sort "password" instead.

To create a key file, on the **local** computer use the command ''ssh-keygen'' and follow it's instructions.
{{:services:remote-access:ssh-keygen.png}}

By default this command produces two files in the ''.ssh'' subdirectory of your home folder.
The file ''id_rsa'' is your **key** file, also called **private key**.
The file ''id_rsa.pub'' is the corresponding **lock**, also called **public key**.

To complete the setup you have to append the contents of ''id_rsa.pub'' to the ''.ssh/authorized_keys'' file on the **remote** computer.
One way to do this is to move ''id_rsa.pub'' from your **local** to the remote computer and then, on the **remote computer** run
<xterm>
cat id_rsa.pub >> .ssh/authorized_keys
</xterm>

Now you should be able to log in using key authentication.