The default username and password for an Ubuntu Linux CD depend on the version of Ubuntu you are using and the installation method you have chosen.
During the installation process, you will be prompted to create a new user account and set a password for it. This user account will be the default user account for the installed system, and it will have full privileges on the system.
If you are using the Live CD version of Ubuntu, which allows you to try out the operating system without installing it, the default username and password are:
ubuntuubuntuKeep in mind that the Live CD version of Ubuntu is intended for testing and evaluation purposes only, and any changes you make to the system will not be saved after you reboot.
If you are installing Ubuntu on a new system, you will need to create a new user account and set a password for it during the installation process. The default username and password for the installed system will be the ones you have chosen during the installation process.
For more information on installing Ubuntu Linux and setting up a user account, you can refer to the Ubuntu documentation or the documentation for the installation method you are using.