The error Error: Can't open display: occurs because the xeyes GUI application cannot connect to an X11 display server. This is a common issue when using ssh -X to forward X11 applications from a remote machine (like your Debian 13 ARM AWS EC2 a1.metal instance) to your local machine (Linux Mint 22.3 Cinnamon).

Here’s how to solve it:

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1. Ensure X11 Forwarding is Enabled on the Server

On your Debian 13 ARM AWS EC2 instance, check if X11 forwarding is allowed in the SSH server configuration:

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sudo nano /etc/ssh/sshd_config

Ensure the following lines are present and uncommented:

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X11Forwarding yes
X11DisplayOffset 10
X11UseLocalhost no

Restart the SSH service:

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sudo systemctl restart ssh

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2. Install X11 Client Utilities on the Server

On the Debian 13 ARM AWS EC2 instance, install the required X11 client utilities:

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sudo apt update
sudo apt install xauth x11-apps

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3. Enable X11 Forwarding on the Client

On your Linux Mint 22.3 Cinnamon machine, ensure that X11 forwarding is enabled when connecting via SSH:

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ssh -X user@your-debian-ec2-ip

• Replace user with your username on the Debian instance.
• Replace your-debian-ec2-ip with the IP address of your EC2 instance.

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4. Verify X11 Forwarding is Working

After connecting, check if the DISPLAY environment variable is set:

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echo $DISPLAY

• If it shows something like localhost:10.0, X11 forwarding is working.

If not, manually set the DISPLAY variable:

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export DISPLAY=localhost:10.0

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5. Test with a Simple X11 Application

Run xeyes again:

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xeyes

• If it works, you should see the xeyes window appear on your local machine.

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6. Firewall and Security Groups (AWS-Specific)

If you're still facing issues, ensure that:

• Your AWS Security Group allows inbound and outbound traffic on port 6010 (X11 uses ports starting from 6000 + display number, e.g., localhost:10.0 uses port 6010).
• Your local firewall (on Linux Mint) allows X11 traffic.

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7. Debugging

If the issue persists, enable verbose SSH output to debug:

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ssh -X -v user@your-debian-ec2-ip

• Look for errors related to X11 forwarding in the output.

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8. Alternative: Use xhost on Local Machine

On your Linux Mint machine, allow connections from the remote host:

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xhost +

• Warning: This allows any host to connect to your X server. Use it temporarily and revoke access afterward with xhost -.

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9. ARM-Specific Considerations

Since you're using an ARM-based EC2 instance (a1.metal), ensure that:

• The xeyes application is compatible with ARM architecture. If not, you may need to install an ARM-compatible version or use a different X11 application for testing.

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Summary of Commands

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