How to safely upgrade critical server software

IF you manage a server - any server - it's going to have all sort of software running on it (common examples are mail servers, database servers and web applications) and software has to be updated from time to time.

From my experience software that is part of "Microsoft web platform" (Windows, the .net framework and IIS plugins provided by Microsoft - not including SQL server) tend to install without problems and update using windows automatic updates without serious issues - most of the time.

3rd party software obviously ranges from completely automated upgrades to almost impossible to update.

Here is the workflow I've adopted to upgrading software on my server, every time I've deviated from this script I've had problems:

1. First, check all the services provided by the server, make sure everything is working - you want to make sure there are no unrelated problems before you start the upgrade.
2. Find the upgrade instruction from the software vendor's web site, make sure you have a copy you can view if the server goes off-line.
3. Find you license files, activation keys and anything else like that.
4. If the software vendor has a portal, log into it, make sure your portal user is associated with your software license (some vendor will require your portal user name and password during installation, this step will make sure you have those).
5. If you don't have physical access to the server log into the control panel that let you turn the server on/off and reboot it remotely (sometimes, you will reboot the server and it will just not come back on-line, having the control panel open will let you force the server to restart in those cases).
6. Download the installation for the new version and any supporting files.
7. Backup your existing data.
8. Read the upgrade instruction carefully, look for any prerequisites and dependencies - make sure they are installed.
9. Now you are ready for the actual work - follow the upgrade instructions carefully.
10. Check the new version is working
11. Verify the new version is not in demo or trial mode, if it is use the licensing info from the 3rd step to re-activate it.
12. Now re-check every other service provided by the server and make sure you didn't break anything else during the upgrade.
13. If you managed to get this far without error - congratulations - you have successfully upgraded critical server software with no issues - if you did get errors now is a good time to contact the support team.

I've just wanted to blog about it so I don't forget any steps in the future, I'd like to hope this will save someone else some downtime but realistically I know we have to make our own mistakes in order to learn from them.

If you have your own upgrade process, recommendation or horror stories feel free to write about it in the comments.