How to create a user with sudo permissions (if booted from the ISO)?

[sudo-joe]

Hello list

just booted my PC from the newly remasterd cubic ISO (Ubuntu 18.04 LTS DVD)

If I try to use "sudo", the following message is shown:

[sudo] password for test:
test is not in the sudoers file. This incident will be reported.

Question:
Is there a way to fix this in the cubic environment before creating the ISO?

Thank you very much in advance for your help!

Joe

PS
By the way, your explanations are excellent in all of my recent posts/questions :)

[PJ-Singh-001]

Here is how to create users for two scenarios:

1. If you want to create one user that is available after installation, use the preseed technique as shown in step 6 here.
   (Be sure to include sudo in the passwd/user-default-groups list).

2. If you want to create user(s) available in the Live environment (and after installation), create the user(s) in Cubic's Terminal page, as shown here.
   (Be sure to execute usermod -a -G sudo <user> for each user that requires sudo privileges).