OS6 on ReadyNAS Pro 4 (RNDP4000)

it is possible to install readynas os 6 on to legacy x86 readynas devices, however it requires a factory default (ie you must backup any data and restore it after).

it is not officially supported by netgear, but they seem to (so far) have been keeping the older hardware working on the ongoing os6 releases.

that is not to say they couldn't drop support at any time, but as of currently the latest os6 releases do work with the legacy devices once they are converted.

I don't know where the current procedures to convert from 4.x to 6.x are anymore, so maybe someone else can either link or re-post them for you.

But basically it involved factory defaulting 4.x device, then using a (older) modfied os6 file, that will overwrite the 4.x firmware on the internal flash, which is then used to a new clean o6 install.

Once the device has been converted to os6, then you can simply upgrade via the UI or normal os6 firmware update procedures.

I have 3 legacy readynas which were all converted to os6 years ago, and have been working and upgraded continously since then.