Mophilly
Koozali sme server upgrade notes are here:
https://wiki.koozali.org/SME_Server:9.0Also see the Backup server config Howto article for various tips on transferring limited data sets, here:
https://wiki.contribs.org/Backup_server_configUsers & groups are spread across various db config files so it is not easily possible to transfer ONLY users & groups, as lots of other db config settings you may not want will also be transferred.
My best suggestion to you is to make notes of important changes you have made to sme8. Remove those hacks & custom templates. Also consider to uninstall contribs. If you have useful contribs installed that have large data sets you want to retain, then leave those installed so the data is included in the backup.
Perform a supported full backup or alternative & use that to restore to your newly installed sme9 operating system.
Then reinstall required contribs & reconfigure custom templates to suit sme 9 requirements.
Also (if not done automatically) remove all sme8 non standard repositories & reconfigure them to suit sme9.