Ruby + Alpine + Docker: git cannot be found when it's installed? - ruby-on-rails

Question

I have a Rails App using Ruby 3 that I deploy using Docker. In my Gemfile I am installing the gem sunspot_rails via github, as the latest official release does not work with Ruby 3:
git_source(:github) { |repo| "https://github.com/#{repo}.git" }
gem 'sunspot_rails', github: 'sunspot/sunspot', glob: 'sunspot_rails/*.gemspec'
In my Production Dockerfile I have a stage which installs the required Gems:
#####################################
# Backend Dependencies
#####################################
FROM ruby:3.0.2-alpine3.14 AS vendor
RUN apk add --no-cache \
sqlite-dev postgresql-dev \
git build-base
# Install backend packages
COPY Gemfile Gemfile.lock ./
RUN bundle config set --local deployment "true" && \
bundle config set --local without "development,test" && \
bundle install
On my local machine, this works fine.
However, when I try to build the image in my CI/CD Pipeline (using drone), I get an error implying that git could not be found:
Fetching https://github.com/sunspot/sunspot.git
Retrying `git clone https://github.com/sunspot/sunspot.git /vendor/bundle/ruby/3.0.0/cache/bundler/git/sunspot-cb781ed3afb1e1091992c51d2c44d880bb461de8 --bare --no-hardlinks --quiet` at / due to error (2/4): Errno::ENOENT No such file or directory - git
Retrying `git clone https://github.com/sunspot/sunspot.git /vendor/bundle/ruby/3.0.0/cache/bundler/git/sunspot-cb781ed3afb1e1091992c51d2c44d880bb461de8 --bare --no-hardlinks --quiet` at / due to error (3/4): Errno::ENOENT No such file or directory - git
Retrying `git clone https://github.com/sunspot/sunspot.git /vendor/bundle/ruby/3.0.0/cache/bundler/git/sunspot-cb781ed3afb1e1091992c51d2c44d880bb461de8 --bare --no-hardlinks --quiet` at / due to error (4/4): Errno::ENOENT No such file or directory - git
According to the logs, git was successfully installed the step before.

Answer 1

I bumped into the same issue with Ruby 3.0.2 and Alpine 3.14 image. Still waiting for CI upgrade, but I locally it works with latest Docker. Alpine requires at least Docker 20.10.0. Check if CI runs recent Docker, kernel or something else like Gitlab runner.

Answer 2

Upgrade to a newer or different version of docker. 22.06.0-beta.0 was the next newer one for me.
In my specific case, I was trying to build a ruby:2.7.5-alpine based docker image on CircleCI. I was getting the same error, Errno::ENOENT No such file or directory - git when git was clearly installed in the Dockerfile step immediately before bundle install. It was working locally.
The docker build command is run inside of a container on CircleCI. I had chosen the latest stable docker image version docker:20.10.17-git for the container.
After reading Ivan's answer to this question, I tried a newer docker version. The only newer image listed on Docker's official images was docker:22.06.0-beta.0-git. Switching to this new image immediately fixed my problem.