Santiago,

the cleanup part in the manifest is used to get rid of files that are not necessary anymore for a specific extension, and is executed during an extension update. The "old" way to do this was to create some text files that holds the information of files to delete,

I delete log files from time to time from /Portals/_default/logs (normally before I do an upgrade of DNN, to have a smaller size of the file backup). I leave those which are only some days old.

Another thing to delete is all files in /install/AuthSystem, /install/Container, /install/JavaScriptLibrary, /install/Language, /install/library, install/Module, /install/Provider and /install/Skin (except the file PlaceHolder.txt) before I unzip the upgrade package over the installation.

When I uninstall an extension, I check if all the files have been deleted (you find this information normally in the manifest of the extension), esp. the assembly (in the /bin folder).

There is propably more to delete and being safe.

Happy DNNing!
Michael

THank you very much @MichaelTobisch. THat's a start. It's been a very long time for me since I developed a module back in the old days so I forgot where to look for the manifest or what it looks like (FileName). Any pointers are greatly appreciated. 

Santiago,

the manifest is normally in the install package, and has a .dnn extension, in some cases you may find it in the installation folder of the extension (e.g. /DesktopModules/xyz/).

The schema is documented here.

Happy DNNing!
Michael