=> ERROR [5/5] RUN npm install or yarn in Dockerfile

I am trying to Dockerise a React app, but when it reaches the command to install npm it throws an error.

My Dockerfile contains:

# pull official base image
FROM node:12.6.0-alpine


# set working directory
RUN mkdir /app
COPY . /app
WORKDIR /app
ENV PATH /app/node_modules/.bin:$PATH

RUN yarn

# start app
CMD ["npm", "start"]

The error is this when it reaches the command to run npm install or yarn:

[5/5] RUN yarn:                                                                                                                             
#9 0.725 yarn install v1.16.0                                                                                                                  
#9 0.789 info No lockfile found.                                                                                                               
#9 0.801 warning package-lock.json found. Your project contains lock files generated by tools other than Yarn. It is advised not to mix package managers in order to avoid resolution inconsistencies caused by unsynchronized lock files. To clear this warning, remove package-lock.json.   
#9 0.809 [1/4] Resolving packages...
#9 1.507 warning [email protected]: Critical security vulnerability fixed in v0.21.1. For more information, see https://github.com/axios/axios/pull/3410
#9 8.363 warning formik > create-react-context > fbjs > [email protected]: core-js@<3.4 is no longer maintained and not recommended for usage due to the number of issues. Because of the V8 engine whims, feature detection in old core-js versions could cause a slowdown up to 100x even if nothing is polyfilled. Please, upgrade your dependencies to the actual version of core-js.
#9 40.35 error Couldn't find the binary git
#9 40.35 info Visit https://yarnpkg.com/en/docs/cli/install for documentation about this command.
------
executor failed running [/bin/sh -c yarn]: exit code: 1

Solution 1:

#9 40.35 error Couldn't find the binary git

Solution: install git in your docker image.

Solution 2:

Install git in your image like this

FROM node:12.6.0-alpine
RUN apk update && apk add git

# set working directory
RUN mkdir /app
COPY . /app
WORKDIR /app
ENV PATH /app/node_modules/.bin:$PATH

RUN yarn

# start app
CMD ["npm", "start"]