Frequently Asked Questions

System

The system does not boot

Verify that you downloaded the correct image, that it is fully downloaded, and that you flashed the decompressed image (not the compressed archive).

If everything looks correct, try downloading the image again to avoid partial downloads.

Remote access

SSH does not work

Factory images enable SSH by default. In most cases, you only need to make sure Cubie A7S and your PC are on the same LAN, then connect via SSH.

Troubleshooting:

1. Check Cubie A7S network connectivity and IP address: use ip a.
2. Confirm Cubie A7S and your PC are on the same LAN: ping each other.
3. Check whether SSH service is running: sudo systemctl status ssh.

VNC does not work

VNC requires manual server configuration. If you follow the tutorial, note that the VNC server will stop after every reboot or shutdown.

Troubleshooting:

1. Complete the VNC configuration steps in the tutorial.
2. Make sure SSH works first.
3. Check whether the VNC server is running: vncserver -list.
4. Connect to ip:5901 where ip is the Cubie A7S IP address.

Serial console

Cannot open the serial device

If you see Error: Permission denied, cannot open /dev/ttyUSB0:

Try the following:

1. Check that the USB‑to‑UART adapter is correctly connected to the PC.

2. Check device permissions.

On Linux, if you do not have permission to access the device, run the following to grant access.

• View device info

For example, using /dev/ttyUSB0:

Linux$

ls -l /dev/ttyUSB0

If the device exists, you will see output similar to:

crw-rw---- 1 root dialout 188, 0 Sep 10 21:24 /dev/ttyUSB0

• Add your user to the dialout group

Linux$

sudo usermod -a -G dialout $USER

• Re-login (or refresh group membership)

Linux$

newgrp dialout

3. Check whether the serial device is in use by another program.

Network bandwidth testing

Port already in use

If you see iperf3: error - unable to start listener for connections: Address already in use, an iperf3 process is already using port 5201.

Fix:

1. Find the iperf3 process

Linux@host$

ps -ef | grep iperf3

2. Kill the iperf3 process (replace <PID> with the actual PID)

Linux@host$

sudo kill <PID>

KDE Discover does not work

KDE Discover uses OpenGL rendering by default. If the current GPU driver does not support OpenGL rendering, KDE Discover may not work. Use apt in the terminal to install packages instead.

Linux@host$

sudo apt search <package_name>
sudo apt install <package_name>

apt supports fuzzy searching. When using apt install, you can press Tab to auto-complete package names.

For example, to install VLC:

Linux@host$

sudo apt search vlc
sudo apt install vlc