by Pablo Hernández.
Right on spot! Thanks a million Leon.
Use
database for session information is off (unchecked).
However, PHP session.save_path is pointing to ~/tmp/, where I could finally find the sess_* files (thought I had searched my fs before but obviously failed).
Two additional questions if I may:
1) Now that I add session.save_path to my google searches I see there are tons of resources, from changing php.ini to adding $CFG entries to config.php. Any best practices you could please recommend?
2) My pre-migration server had 238 session files in total after a few months of service, the new server already has 5,520 session files (and growing by the minute) after only 4 days. Files are +/- evenly distributed by date, with some ~1,380 files per day. I only have 476 registered users.