Sudo cannot be used because sudoers permissions are mistakenly Modified In Ubuntu (you can retrieve the sudo permission when you forget the root password)

In Ubuntu, the sudoers permission cannot be changed by mistake (you can retrieve the sudo permission when you forget the root password). Because the sudoers permission is modified, sudo cannot be used, it happens that the Ubuntu root password is not set, and the result can only be modified in the single-user mode (with root power). In Ubuntu, during the boot, press shift to display various modes. Select the second recovery mode, press e to edit the file. The page is changed to rw single init =/bin/bash. Press ctrl + x to enter the single-user mode, you can use the root permission to modify what you want to change!