use the systemMediaSize=min boot option when launching the installer. This option reduces the ESX‑OSData partition to approximately 24 GB of usable space (the theoretical minimum is 33 GB, but in practice it uses around 24 GB).
If your target hardware uses consumer-grade hardware (like Realtek NICs or Intel NUCs), the default ISO will halt with a "No Network Adapters" error. You must inject community drivers (Community VIBs) into the ISO before flashing it. esxi 70 download iso portable