After installing ua-netinst, on a Pi 3 model B v1.2, I get a rainbow screen.
This may be because the card has just not been done right from the beginning, although if it ends up changed something is going on. Maybe.
If, after you prep the card, insert it for the first time, and power on the pi, you see the green ACT light flickering intermittently, then it is booting and presumably ua-netinst is doing its thing.
If instead you just see the green ACT light on solid or not at all, the card is not properly formatted and nothing is happening.
From the comments here, this is expected and I need to re-copy the start.elf, start_cd.elf, start_db.elf and start_x.elf file to the SD card.
I would regard those comments a little bit like directions you might get on the sidewalk late at night from someone stumbling drunk. This person may or may not have any idea what they are talking about, but it certainly reads like a blind guess (keeping in mind there is such thing as "dumb luck"). And/or I'm not so sure the context the comments are made in are what you are assuming they are.
You should not have to do anything beyond what is explained here:
Format your SD card as FAT32 (MS-DOS on Mac OS X) and extract the installer files in.
- Format the card.
- Unzip the ua-netinst zip file.
- Copy everything from the zip file onto the FAT32 formatted card.
Then go to this step, which does include "cross your fingers" in the description.
Beware that while
ua-netinst should work with the Pi 3 since it is (presumably...) just installing the latest Raspbian over top of itself, the last time ua-netinst was updated was before the Pi 3 was released, and there are some files required to make the 3 work specific to it that need to end up on the first partition. If that isn't happening, you will have problems.
Also beware that ua-netinst is I think at best "cross your fingers" friendly from a complete novice perspective. Your life will be much, much, much easier if you can get access to an HDMI display and keyboard for an evening and just install Raspbian the normal way. You learn to walk before you run and all that.