The client software for Windows (v1.4.14.34018) and Linux is also officially EOSL but may be accessible via the Lenovo Support Portal if you can provide a valid serial number. How to Install / Reflash via USB
This is the operating system that runs directly on the ix2 hardware. Without the correct firmware, your NAS is just a plastic box with spinning drives. The latest version for the ix2 is typically Lenovo LifeLine 4.1.111 or a similar 4.1.x build. lenovo ix2 software download