Server upgrades.

Upgrading the operating system on your home machine is a piece of cake compared to doing it in the server environment, Generally when you care changing a server os, you use a new systems so that if there are issues you can go back to the old system as a failsafe. There are always issues setup up new operating systems especially with hardware drivers, so dealing with that can be fun.

When you set up a new system the storage formats are completely different.   Some applications will balk at that, In some cases it could be just a permissions problem. Also network printers and input devices have to be set up. Remembering once when we went from Novell to NT printing out student invoices did not work or barely worked. The consulting company said it worked when they tested it, but never really did a mass testing. We ended up pooling printers to make things work well enough till a better fix was done.

To add to that scenario, you have to make sure the general permissions of files are correctly setup. For instance, years ago everything was locked down on Novell, Microsoft there was no real security, so you had to go directory, and file by file and change as needed.

There were always server applications that did not want to work with the newer systems OS applications could and will fail, This is especially true with specific permissions access.  You will need to make adjustments to allow your applications work in the new environment. . This was even true between versions of Microsoft servers. You would have to contact vendors for fixes and updates which on many cases the vendors were reluctant to do. In many cases you had to perform miracles on your own to make things work,  That led to issues, because vendors would threaten to sue you if you changed their software for copyright and or other violations.

Once you had that done, you had to go application by application to make sure the clients interacted with the server properly. This meant you had to completely revise your control (batch, shell, etc) files because the same scripts would no longer work anymore. Then you had to go to the clients and correct shortcuts to connect to the new control files. We usually just built a new image to work with.  Then there was the testing and retesting to make sure everything worked, That was just the tip of the iceberg.. Moving on, Of course, all this had to be done without the user ever knowing a change was made.  Being a software administrator is so much fun,