my notes on upgrading Ubuntu 16.04 to 18.04

The upgrade of simple setups is going expectedly smooth
As usual, I add Bionic repositories along with Xenial's and upgrade all packages using apt, like this :

cd /etc/apt/sources.list.d
sed 's/xenial/bionic/g' < xenial.list > bionic.list
apt update
apt install apt dpkg perl
apt autoremove
apt upgrade
apt autoremove
apt dist-upgrade
apt autoremove
rm xenial.list
apt update
reboot

After the reboot, I review 'Obsolete and locally-installed packages' with 'aptitude' and remove what I don't need ('initscripts', 'sysv-rc', 'insserv' and some orphaned libs). Also I review 'journalctl' for red spots, and various application logs possibly affected by the upgrade

notes collected on more complex setups:

• if you have EFF 'certbot' installed from separate xenial/certbot apt source, remove this source before upgrade, as Bionic has its own certbot packages


• PHP is upgraded from 7.0 to 7.2 and renames its FPM socket with the new version. Reflect this change in your web server configuration. Also I had to update yii2 package within one older application ('composer update') which had conflict over the 'Object' class name in the older yii2 version


• Java is updated to v10.0.1 with apparent intention to update it to v11 (package names with 'jdk-11' and directory names with 'java-11'). To fix a problem arisen on one of my systems, I had to follow a StackOverflow recipe and add '--add-modules java.xml.bind' to 'JAVA_OPTS' in '/etc/default/tomcat8'. To run Nexus OSS v2, add this string to the environment variable 'JDK_JAVA_OPTIONS'