Copying users and authorizations to another system

How can I copy all users and all authorizations to another system and/or client? And if I do this, will all users and authorizations in the target system be overwritten? To copy all users and their respective authorizations from one system into another you can export them via SCC8, copy profile SAP_USER. And, yes. The users and their authorizations in the target system will be overwritten once you import the ones from the source system.