Unable to boot macOS, macOS recovery and macOSinternet with rEFInt

[daniele]

iMac with dual boot: macOS Sierra and Ubuntu MATE.
I installed rEFInt and everything was working well, I could start both macOS and Ubuntu.

Last week, during the macOS updating process, my home internet connection dropped down. It had been kept down for hours. As the upgrade process seemed to be freezed I performed a shut-down by pressing the power bottom.
Now I try to complete the updating process but macOS doesn't start any more.
Even the macOS recovery (still present in a partition on my HD) doesn't start.
Meanwhile Ubuntu is starting as before.

Can I perform OSX Internet boot? How?

Thanks in advance

Daniele

[Roderick W. Smith]

I recommend you check on Mac forums for information on downloading the Mac installer and writing it to a USB flash drive or DVD, then install from that. Unfortunately, I don't have step-by-step instructions handy. A big caveat: The instructions I've seen for this have all assumed a working macOS installation, so you may need to use another computer, dig a while to find something that'll work from Linux, or figure out how to adapt the instructions yourself.