Originally published at: https://www.cyberciti.biz/faq/aws-lightsail-upgrade-ubuntu-16-04-lts-to-18-04-lts/
By default, Lightsail will install Ubuntu 16.04 LTS. How do I upgrade to Ubuntu Linux 18.04 LTS when using AWS Lightsail cloud server? How do I upgrade to a newer version of Ubuntu such as Ubuntu Linux 18.04 LTS?