Docker uses the Ubuntu20.04 Unity desktop, and the startup command to set the password is as follows.
sudo docker run -it -p 5901:5901 -p 6080:6080 -p 4040:4040 -e PASSWORD=123456 --privileged --name ubuntu-unity-novnc land007/ubuntu-unity-novnc:20.04Visit http://127.0.0.1:6080/vnc.html in your browser,
After booting, you can remotely display the following address. The password is 123456. This password is the VNC connection and the ubuntu password.
You can also use a random password as follows.
#Start
sudo docker rm -f ubuntu-unity-novnc; sudo docker run -it -p 5901:5901 -p 6080:6080 -p 4040:4040 --privileged --name ubuntu-unity-novnc land007/ubuntu-unity-novnc:20.04
#View password
sudo docker exec ubuntu-unity-novnc cat /home/ubuntu/password.txt