These update procedures contain only essential information and best practices for updating a running ubuntu server and keeping the downtime low.
Ubuntu 16.04.6 to Ubuntu 18.04
Backup – If you use a cloud hoster like digitalocean, create a snapshot. It’s recommended to power off the VM before creating the snapshot for keeping file integrity. If you do not use a virtual machine or cloud hoster, it is recommended to make a copy of the entire file system. At least you need to back up the directories /home, /etc and /var
Update Installed Packages
Before beginning the release upgrade, it’s recommended to update to the latest versions of all packages for the current release. Update the package list:
sudo apt-get update
Next, upgrade installed packages to their latest available versions:
sudo apt-get upgrade
When this is finished use the command below. This will execute additional updates that require changing dependencies, adding, or removing new packages if necessary. It will process upgrade steps which may have been kept back by apt-get upgrade.
sudo apt-get dist-upgrade
Upgrade Ubuntu to 18.04
sudo do-release-upgrade
Update from MySQL 5.7 to 8.0
Download package config
wget -c https://dev.mysql.com/get/mysql-apt-config_0.8.14-1_all.deb
reconfigure packages
sudo dpkg -i mysql-apt-config_0.8.13-1_all.deb
Update packages
sudo apt-get update
Update MySQL
sudo apt install mysql-client or mysql-server