Postgres tablespace on mounted usb
PostgreSQL won't run off NTFS on Linux. Format the drive as ext4.

Frankly, putting a database on a USB key on a tablespace isn't usually a great idea. The tablespace is unreadable without the rest of the database, and the rest of the database is useless without the tablespace. So you're creating a fragile system with two points of failure.

It's a much better idea to instead move the whole PostgreSQL data directory onto the USB drive.