I often install new Linux virtual machines where I’m the only interactive user and so I see no sense in entering password every several minutes. Unfortunately, sudoers syntax is not at all intuitive, so every time I need to google for the same lines to be added.

• Run sudo visudo.
• Update the %sudo line to be:

  %sudo   ALL=(ALL:ALL) NOPASSWD: ALL
  

Update: In Ubuntu 20.04, installer created a file in /etc/sudoers.d/ which overrode the setting in sudoers. I removed it.