update merlin6 nomachine docs

docs/merlin6/how-to-use-merlin/connect-from-linux.md

@@ -0,0 +1,42 @@
+# Connecting from a Linux Client
+
+## SSH without X11 Forwarding
+
+This is the standard method. Official X11 support is provided through [NoMachine](nomachine.md).
+For normal SSH sessions, use your SSH client as follows:
+
+```bash
+ssh $username@merlin-l-01.psi.ch
+ssh $username@merlin-l-001.psi.ch
+ssh $username@merlin-l-002.psi.ch
+```
+
+## SSH with X11 Forwarding
+
+Official X11 Forwarding support is through NoMachine. Please follow the document
+[{Job Submission -> Interactive Jobs}](##/merlin6/interactive-jobs.html#Requirements) and
+[{Accessing Merlin -> NoMachine}](nomachine.md) for more details. However,
+we provide a small recipe for enabling X11 Forwarding in Linux.
+
+* For enabling client X11 forwarding, add the following to the start of `~/.ssh/config`
+to implicitly add `-X` to all ssh connections:
+
+   ```bash
+   ForwardAgent yes
+   ForwardX11Trusted yes
+   ```
+
+* Alternatively, you can add the option `-Y` to the `ssh` command. In example:
+
+   ```bash
+   ssh -X $username@merlin-l-01.psi.ch
+   ssh -X $username@merlin-l-001.psi.ch
+   ssh -X $username@merlin-l-002.psi.ch
+   ```
+
+* For testing that X11 forwarding works, just run `xclock`. A X11 based clock should
+popup in your client session:
+
+   ```bash
+   xclock
+   ```