Build and Install Tools Using Containers

Another challenge in my quest to not have any programming languages installed directly on my computer is installing programs that need to be built from source. I’ve been using jj in place of Git for the last few months¹. To install it you can either download the pre-build binaries, or build from source using cargo. When I first started using it there was a minor bug that was fixed on main but not the latest release, so I needed to build and install it myself instead of just downloading the binary.

Naturally the solution is to hack around it with containers. The basic idea is to use an base image that matches the host OS (Ubuntu images for most languages are not hard to come by) and build in that, and only copy the executable out into the host system.

To install jj and scm-diff-editor I make a Containerfile like this:

FROM docker.io/library/rust:latest
WORKDIR /src
RUN apt install libssl-dev openssl pkg-config
RUN cargo install --git https://github.com/martinvonz/jj.git --locked --bin jj jj-cli
RUN cargo install --git https://github.com/arxanas/git-branchless scm-record --features scm-diff-editor
COPY install.sh .
ENTRYPOINT /src/install.sh

This just runs the necessary cargo commands to install the two executables in the image. The install.sh script is super simple, it just copies the executables from the image into a bind-mounted folder:

#!/bin/bash
for bin in jj scm-diff-editor; do
  cp "$(which "$bin")" "/output/$bin"
done

So the last part is just putting it all together with a pod config file:

images:
  jj-install:
    tag: jj-install:latest
    from: Containerfile
    build_flags:
      cache-ttl: 24h

containers:
  install:
    name: jj-install
    image: jj-install:latest
    interactive: true
    autoremove: true
    bind_mounts:
      ~/.local/bin: /output

I can then run pod build to create a new image and build new executables with cargo. Then pod run the container to copy them out of the image and into the $PATH on my host system.

This is the same approach I used for the automatic install script for pod itself—except using podman commands directly rather than a pod config. I’ve done the same thing to install rubyfmt since that is only packaged with Brew, or requires Cargo to build from source.

I’m sure at some point an incompatibility between libraries inside and outside of the container will create a whole host of bizarre issues, but until then I will continue using this approach to install things.