How to upgrade your linux server

How do you do an in place upgrade on a older Linux Server and why would you want to.  Well why you would want to is obvious, security patches, and giving longer life to the server on the newer software; that is a good reason.  With browsers being constantly upgraded, along with security issues being found every other day it seems, staying up to date is just a good idea.

So how do we stay up to date?

Typically, if you have been staying up to date you will eventually get prompted to do an upgrade to an newer version of linux at some point.  All the following commands will need to be run as root (sudo).

sudo apt-get update

Downloads package information from all configured sources.  Running this command keeps your package information up-to-date

sudo apt-get upgrade

This command only upgrades.  The upgrades are only upgrades available to the platform, as defined in /etc/apt/sources.list or in /etc/apt/sources.list.d/.  This upgrades your packages, not your OS and it will not remove packages.

sudo apt-get dist-upgrade, 

Intelligently installs or removes packages as needed.  This command has a smart conflict resolution system.  The system attempts to upgrade the most important packages, at the expense of those deemed less important.  This command will also delete software if it is required to complete the upgrade process.

sudo apt-get autoremove

Removes packages that were automatically installed because another package required them but, if they are no longer needed this command removes them.

sudo apt-get autoclean

Clears the local repository of retrieved package files, but it only removes files that can no longer be downloaded and are virtually useless. It helps to keep your cache from growing too large

sudo do-release-upgrade

The do-release-upgrade command will upgrade the system from one release to another. This is the command you want if you want to upgrade from Ubuntu 18.04 to 20.04.  NOTE:  The system must be fully upgraded to run. use the apt-get upgrade, followed by sudo apt-get dist-upgrade commands before running the do-release-upgrade command.

Sources

https://www.digitalocean.com/community/questions/updating-ubuntu-16-04-to-20-04
https://www.techrepublic.com/article/how-to-tell-the-difference-between-apt-get-upgrade-apt-get-dist-upgrade-and-do-release-upgrade/