Licallo/Troubleshooting.md

@@ -53,23 +53,33 @@ unset I_MPI_PMI_LIBRARY
 mpirun -n $SLURM_NTASKS ./dice
 ```
 ## X11 Forwarding
-### On mac os : xquartz is mandatory to use X11 applications
+### On mac OS : **xquartz** is mandatory to use X11 applications
 
 **Symptom**
 
-On mac, impossible to use a graphic page
+When connecting on a server from a mac through `ssh licallo -X`, the X11 forwarding fails.
+
+```
+xxx@dhcp20-65 ~ $ ssh -X xxx@licallo.oca.eu
+mfabian@hal7.oca.eu's password: 
+Warning: untrusted X11 forwarding setup failed: xauth key data not generated
+[xxx@licallo ~]$ xeyes
+Error: Can't open display: 
+```
 
 **Solution**
+(requires sudo privilege on the client)
  
+Edit the `/etc/ssh_config` file and add/changed line:
 ```
-edit ssh_config
-add /changed line
 XAuthLocation /opt/X11/bin/xauth
+```
+
+**Explanation**
 
-explications :
-ssh -X should work since XQuartz, once enabled, uses xauth.
-he only problem is that ssh is looking for xauth in /usr/X11R6/bin and on macOS with XQuartz it is in /opt/X11/bin
+`ssh -X` should work since **XQuartz**, once enabled, uses xauth.
+he only problem is that *ssh* is looking for xauth in `/usr/X11R6/bin` instead of `/opt/X11/bin` as it is on macOS with **XQuartz**
 
 ```
-source: https://stackoverflow.com/questions/27384725/ssh-x-warning-untrusted-x11-forwarding-setup-failed-xauth-key-data-not-gener
+[source](https://stackoverflow.com/questions/27384725/ssh-x-warning-untrusted-x11-forwarding-setup-failed-xauth-key-data-not-gener)