Cannot install gems from git in dockerized rails app

Question

Please, help me with building my first docker image. My Gemfile contails:

gem 'webpacker', github: 'rails/webpacker'

Here is Dockerfile:

FROM ruby:2.4-alpine

...
ADD Gemfile $INSTALL_PATH/Gemfile
ADD Gemfile.lock $INSTALL_PATH/Gemfile.lock
RUN bundle install
ADD . $INSTALL_PATH
...

Docker and docker-compose:

Docker version 17.03.1-ce, build c6d412e
docker-compose version 1.13.0, build 1719ceb

When I run

docker build .

I receive errors:

Fetching https://github.com/rails/webpacker.git
sh: git: not found

Git error: command `git clone 'https://github.com/rails/webpacker.git'
"/usr/local/bundle/cache/bundler/git/webpacker-
61415c05b31197242a5fde705ba334f36321be12"
--bare --no-hardlinks --quiet` in directory /test_task has failed.

I guess, the reason is related with github source, because if I remove all gems with github source from Gemfile, then gems will be fetched correctly from rubygems repository

Upd: when I use ruby:2.4-slim instead of alpine linux as base image, then build completes without errors

Answer 1

It seems you don't have git inside the container. To install it on an Alpine image, you should add to your Dockerfile this:

FROM ruby:2.4-alpine
RUN apk update && apk add git
... the rest of your Dockerfile ...

Hope it helps.