# Minimal Base Python Container Image

The *pythonctnr* image contains ONLY the Python runtime, and nothing else.  It
is suitable for deploying applications written in pure Python, without any
external library dependencies.  No shell or other OS utilities are included.
Just `/usr/bin/python3` and the libraries it needs to run.


## Building

The contents of the container image are built with [buildroot][0].

```sh
make -C ~/src/buildroot O=${PWD}/_build pythonctnr_defconfig
make -C _build
```

This will produce a `rootfs.tar` tarball in `_build/images`, which is then
converted to a container image using `buildah`.

```sh
ctnr=$(buildah from scratch)
buildah add ${ctnr} _build/images/rootfs.tar /
buildah commit ${ctnr} pythonctnr:latest
```

[0]: https://buildroot.org/


## Usage

The container image can be used like any other image, e.g. in a `Dockerfile`.
*pip* is included, to allow installing Python distribution packages.

```Dockerfile
FROM pythonctnr

RUN ["/usr/bin/python3", "-m", "pip", "install", "mypkg"]
```

**NOTE**: Because there is no shell, the default string form of the `RUN`
instruction does not work.  You must use the *exec* form.