Prerequisites for Installing Rails on Windows

• 2018/08/05

Setup

I tested on:

• Windows 10 (64-bit)
• Ruby 2.4
• Rails 5.2

Where it failed

Running

gem install rails

from the prompt threw an error complaining that msys2 was missing, and gem list --local confirmed the install never completed. Naturally rails -v did not work either.

Root cause and fix

• During the Ruby installer flow there is a screen that lets you install msys2. I skipped it, which caused the failure.
• You can apparently install msys2 separately, but I reinstalled Ruby instead.

After reinstalling Ruby, a prompt opens automatically. Do not press Enter immediately—follow these steps:

1. Type 1 and press Enter to install.
2. Type 2 and press Enter to update.
3. Type 3 and press Enter to install the MINGW toolchain.

I do not know every detail, but it seems required so Ruby can compile native extensions written in C.

Finally, rerun:

gem install rails

and the installation succeeds.