Add hint on juron -XF

Batch-Systems.md

@@ -14,6 +14,11 @@ Important commands:
 * Open interactive pseudo-terminal shell (`-tty`): `bsub -tty -Is /bin/bash`
 * With GPU resources (`-R […]`): `bsub -R "rusage[ngpus_shared=1]" -tty -Is /bin/bash`
 * Forward X, e.g. for *Visual Profiler* (`-XF`): `bsub -R "rusage[ngpus_shared=1]" -I -XF nvvp`
+    - Trouble with this? Make sure you have done the following<a name="xftrouble"></a>
+        + On your local machine, add the `id_train0XX` SSH key to your agent with `ssh-add id_train0XX`
+        + Connect to JURON forwarding your SSH agent (`ssh -A […]`)
+        + On JURON, verify that the system knows your `id_train0XX` key with `ssh-add -l`
+        + *Hint: Have a look at the **Creating Alias** part of the `Login.{md,pdf}` section of the documentation. Much better than creating aliases in your shell.*
 * Use node in exclusive mode (`-x`): `bsub -x -I hostname` (*Please keep your exclusive jobs short*)
 
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