Add TensorBoard JupyterHub documentation

doc.zih.tu-dresden.de/docs/software/tensorboard.md

@@ -3,19 +3,44 @@
 TensorBoard is a visualization toolkit for TensorFlow and offers a variety of functionalities such
 as presentation of loss and accuracy, visualization of the model graph or profiling of the
 application.
-On ZIH systems, TensorBoard is only available as an extension of the TensorFlow module. To check
+
+## Using JupyterHub
+
+The easiest way to use TensorBoard is via [JupyterHub](../access/jupyterhub.md). The default
+TensorBoard log directory is set to `/tmp/<username>/tf-logs` on the compute node, where Jupyter 
+session is running. In order to show your own directory with logs, it can be "sym-linked" to the 
+default folder. Open a "New Launcher" menu (`Ctrl+Shift+L`) and select "Terminal" session. It 
+will start new terminal on the respective compute node. Create a directory `/tmp/lazariv/tf-logs`
+and link it with your log directory 
+`ln -s <your-tensorboard-target-directory> <local-tf-logs-directory>`
+
+```Bash
+mkdir -p /tmp/$USER/tf-logs
+ln -s <your-tensorboard-target-directory> /tmp/$USER/tf-logs
+```
+
+Update TensorBoard tab if needed with `F5`.
+
+## Using TensorBoard
+
+On ZIH systems, TensorBoard is also available as an extension of the TensorFlow module. To check
 whether a specific TensorFlow module provides TensorBoard, use the following command:
 
-```console
+```console hl_lines="9"
 marie@compute$ module spider TensorFlow/2.3.1
 [...]
-Included extensions
-[...]
+        Included extensions
+        ===================
+        absl-py-0.10.0, astor-0.8.0, astunparse-1.6.3, cachetools-4.1.1, gast-0.3.3,
+        google-auth-1.21.3, google-auth-oauthlib-0.4.1, google-pasta-0.2.0,
+        grpcio-1.32.0, Keras-Preprocessing-1.1.2, Markdown-3.2.2, oauthlib-3.1.0, opt-
+        einsum-3.3.0, pyasn1-modules-0.2.8, requests-oauthlib-1.3.0, rsa-4.6,
+        tensorboard-2.3.0, tensorboard-plugin-wit-1.7.0, TensorFlow-2.3.1, tensorflow-
+        estimator-2.3.0, termcolor-1.1.0, Werkzeug-1.0.1, wrapt-1.12.1
 ```
 
 If TensorBoard occurs in the `Included extensions` section of the output, TensorBoard is available.
 
-## Using TensorBoard
 
 To use TensorBoard, you have to connect via ssh to the ZIH system as usual, schedule an interactive
 job and load a TensorFlow module:

[Elias Werner]

tmp/<username>/tf-logs or tmp/marie/tf-logs ?

[Taras Lazariv]

I would suggest using <username>

[Martin Schroschk]

I go with Taras.