MoTTY X11 proxy: No authorisation provided

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• 28 Aug, 2025
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• 51 Secs Read

MoTTY X11 proxy: No authorisation provided

Error

MoTTY X11 proxy: No authorisation provided
java.lang.NoClassDefFoundError: Could not initialize class sun.awt.X11.XToolkit

Causes:

• $DISPLAY is not correctly set,

• xauth is missing or not configured,

• or .Xauthority is not being used or trusted.

Solution:

Step 1: Confirm xauth is installed

which xauth

If it returns nothing:

sudo yum install xauth # RHEL/CentOS
# or
sudo apt install xauth # Debian/Ubuntusudo yum install xauth # RHEL/CentOS
# or
sudo apt install xauth # Debian/Ubuntu

Step 2: In session config:

• Go to Advanced SSH settings

• ✅ Ensure “X11 forwarding” is checked

Step 3: Verify environment variable

After login, run:

echo $DISPLAY

Expected output:

localhost:10.0

Step 4: Generate .Xauthority entries

xauth list

If it returns nothing or errors:

xauth generate $DISPLAY . trusted

Then re-check:

xauth list

Step 5: Test with lightweight GUI app

xclock

If xclock opens a window on your Windows desktop → SUCCESS ✅

Step  6 : Check output of below command

echo $DISPLAY
xauth list

export DISPLAY=localhost:10.0
xclock

If above one is failed

Step 7: Install xclock

sudo yum install xorg-x11-apps -y

Re-run the test

xclock