Installing haskell's cabal or ghcup inside a dockerfile wont work - docker

Question

This is my dockerfile for haskell:
FROM ubuntu:focal
RUN apt-get update && apt-get install -y build-essential curl \
libffi-dev libffi7 libgmp-dev libgmp10 \
libncurses-dev libncurses5 libtinfo5
ENV BOOTSTRAP_HASKELL_NONINTERACTIVE=1
RUN sh -c "curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | sh"
RUN sh -c "curl -sSL https://get.haskellstack.org/ | sh"
even though it install ghcup I cannot run cabal neither ghcup.
What is wrong?
Even running this inside the docker container in bash will say
[ Warn ] Cabal ver 3.4.0.0 already installed; if you really want to reinstall it, you may want to run 'ghcup rm cabal 3.4.0.0' first
but I cannot launch cabal or ghcup.

Answer 1

ghcup maintainer here.
I recommend to use ghcup as follows in Docker, which will not require messing with PATH:
FROM ubuntu:focal
ARG DEBIAN_FRONTEND=noninteractive
ENV TZ=Europe/Berlin
# install dependencies
RUN \
apt-get update -y && \
apt-get install -y --no-install-recommends \
curl \
libnuma-dev \
zlib1g-dev \
libgmp-dev \
libgmp10 \
git \
wget \
lsb-release \
software-properties-common \
gnupg2 \
apt-transport-https \
gcc \
autoconf \
automake \
build-essential
# install gpg keys
ARG GPG_KEY=7784930957807690A66EBDBE3786C5262ECB4A3F
RUN gpg --batch --keyserver keys.openpgp.org --recv-keys $GPG_KEY
# install ghcup
RUN \
curl https://downloads.haskell.org/~ghcup/x86_64-linux-ghcup > /usr/bin/ghcup && \
chmod +x /usr/bin/ghcup && \
ghcup config set gpg-setting GPGStrict
ARG GHC=8.10.7
ARG CABAL=latest
# install GHC and cabal
RUN \
ghcup -v install ghc --isolate /usr/local --force ${GHC} && \
ghcup -v install cabal --isolate /usr/local/bin --force ${CABAL}
You can read about isolated installations here.

Answer 2

You have to include their paths to PATH in order to be discoverable.
In addition, I prefer to use bash instead of sh.
This one is working as expected and note the two different ways to declare ENV variables as also some common commands:
FROM debian:stable-slim as build
# Install dependencies *You don't need all of them
RUN apt-get update -y \
&& apt-get upgrade -y \
&& apt-get install -y git jq bc make automake libnuma-dev \
&& apt-get install -y rsync htop curl build-essential \
&& apt-get install -y pkg-config libffi-dev libgmp-dev \
&& apt-get install -y libssl-dev libtinfo-dev libsystemd-dev \
&& apt-get install -y zlib1g-dev make g++ wget libncursesw5 libtool autoconf \
&& apt-get clean
# Install ghcup
ENV BOOTSTRAP_HASKELL_NONINTERACTIVE=1
RUN bash -c "curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | sh"
RUN bash -c "curl -sSL https://get.haskellstack.org/ | sh"
# Add ghcup to PATH
ENV PATH=${PATH}:/root/.local/bin
ENV PATH=${PATH}:/root/.ghcup/bin
# Install cabal
RUN bash -c "ghcup upgrade"
RUN bash -c "ghcup install cabal 3.4.0.0"
RUN bash -c "ghcup set cabal 3.4.0.0"
# Install GHC
RUN bash -c "ghcup install ghc 8.10.4"
RUN bash -c "ghcup set ghc 8.10.4"
# Update Path to include Cabal and GHC exports
RUN bash -c "echo PATH="$HOME/.local/bin:$PATH" >> $HOME/.bashrc"
RUN bash -c "echo export LD_LIBRARY_PATH="/usr/local/lib:$LD_LIBRARY_PATH" >> $HOME/.bashrc"
RUN bash -c "source $HOME/.bashrc"
# Update cabal
RUN bash -c "cabal update"