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====== Remote Access to your Workstation ======
For security reasons, access to your Lorentz workstation is only possible within the Lorentz network.

==== Example 1 ====

Should you want to open an ssh session to your workstation and you are located outside the Lorentz network you can tunnel your request through ''ssh.lorentz.leidenuniv.nl''. For example
<code>
ssh -f <your_username>@ssh.lorentz.leidenuniv.nl -L 2222:<your_workstation>.lorentz.leidenuniv.nl:22 -N
</code>
instructs your machine to `tunnel' requests to local port 2222 through ''ssh.lorentz.leidenuniv.nl'' to finally reach port 22 (sshd) on your workstation. Use ''ps'' to see if the command above executed successfully <code>
ps  aux | grep ss[h]
your_username   6217  0.0  0.0  89612  2948 ?        Ss   13:19   0:00 ssh -f your_username@ssh.lorentz.leidenuniv.nl -L 2222:your_workstation.lorentz.leidenuniv.nl:22 -N
</code>
At this point you are ready to initiate an ssh session to your workstation
<code>
ssh -p 2222 localhost
</code>

NOTE: Should you want ssh to set the DISPLAY environment variable, you can use option ''-X'' when you run ssh. You can invoke the ssh manual pages by typing ''man ssh''.


==== Example 2 ====
Case scenario: you are at home and you would like to connect to your workstation named `asselijn'.
Locally (e.g. on your laptop), create a file ''.ssh/config'' with a section for the machine to which you want to log in, containing the ProxyCommand ssh option to do the tunnelling:
<code>
Host asselijn.lorentz.leidenuniv.nl asselijn
ProxyCommand /usr/bin/ssh -W %h:%p ssh.lorentz.leidenuniv.nl
</code>
And if you have a different username locally and on the institute desktops, that can be added like this:
<code>
Host asselijn.lorentz.leidenuniv.nl asselijn
ProxyCommand /usr/bin/ssh -W %h:%p username@ssh.lorentz.leidenuniv.nl
User username
</code>
If you need access to multiple hosts, just copy and edit the example above.

==== Example 3 ====
You sit in your office at the IL and have started a jupyter notebook on marisXX port YYYY. To connect to your notebook using the browser on your workstation you must tunnel through `novamaris'. Edit your local .ssh/config
<code>
Host maris
   HostName novamaris.lorentz.leidenuniv.nl
   LocalForward YYYY localhost:YYYY

Host marisXX
   HostName marisXX
   ProxyJump maris
   LocalForward YYYY localhost:YYYY

</code>

You are now ready to tunnel your connections through novamaris and visualize your notebook at ''http://localhost:YYYY''.

**NOTE**: For this to work your workstation must have OpenSSH v7.3+.

==== Example 4 ====
Same situation as in Example 3 but this time you sit behind your laptop at home.

<code>
Host lorentz
     HostName ssh.lorentz.leidenuniv.nl
     User <your-IL-username>
     IdentityFile ~/.ssh/id_rsa

Host maris
     HostName novamaris.lorentz.leidenuniv.nl
     ProxyJump lorentz
     IdentityFile ~/.ssh/id_rsa
     User <your-IL-username>

Host marisXX
     HostName marisXX.lorentz.leidenuniv.nl
     ProxyJump maris
     IdentityFile ~/.ssh/id_rsa
     User <your-IL-username>
     LocalForward YYYY localhost:YYYY
</code>

==== Example 5: Using Putty ====
You will need to open two putty sessions. The first one opens a tunnel, the second one uses it. For the sake of clarity let us call the first session `Tunnel' and the second one `Tunnel_use'. In this example we will establish a connection to the Maris headnode ''novamaris'' through an ssh tunnel on ''ssh.lorentz.leidenuniv.nl''. 
=== Session 1: Tunnel ===
Open putty and create a session called Tunnel, then set it according to the snapshots below

{{ :institute_lorentz:tunnel1.png |}}

{{ :institute_lorentz:tunnel2.png |}}



Please note the settings in the port forwarding panel. We use an arbitrary port (2222), but you can choose any numbers above 1024 provided they are not currently in use. By pushing `Open', a terminal will appear so that you can authenticate using your Lorentz institute credentials. Leave this terminal open and proceed
with the creation of session `Tunnel_use'

{{ :institute_lorentz:tunnel3.png |}}

Now push `Open' and a terminal will appear asking your authentication credentials on ''novamaris''. Any other putty connection to ''localhost:2222'' will ssh directly to ''novamaris''.
===== VNC: GNU/Linux =====
For detailed instructions on how to set up a vnc session you are encouraged to follow [[:vnc|these]] 
instructions.

Finally, take a look at [[linux:x2go|x2go]] should you be interested.
===== VNC: Windows Users =====
Please read [[linux:putty|here]].

===== Proxy Browsing =====
Read [[:china|here]]
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