Best project management software for a system migration?

We are migrating a very old computer system that runs virtualized on top of AIX to being virtualized on top of CentOS Linux. The details aren't that important, but there are a bunch of things that could potentially break as the result of software updates and other issues that will be different between the two systems.

This is a system that has been developed over 40 years, and there is a huge amount of tribal knowledge. I think management isn't even aware of all the processes that are run on it.

We need a system for people to log their daily computer processes and then sign off that they are working on the new system once migrated. Approximately 100 employees using the system in different capacities.

Thoughts on the best way to handle this?