Hi
You can do the migration kindly follow the steps
1. On exiting Trex on windows OS take the backup of business index objects using python script. by using the SAP Note 975965 - TREX 7.0/7.1: Data backup (online) and recovery
2. Install and configuration the Trex 7.1 on linux OS, refer the SCN link
TREX 7.1 INSTALLATION ON LINUX and connection to SAP ERP 6
3. Restore the Index object from the backup.
BR
SS