Use docker base image provide the needed dependencies.

Dockerfile

@@ -1,30 +1,30 @@
-FROM debian:stretch-slim
+FROM docker:stable
 MAINTAINER Jan Boonen <[email protected]>
 
 ARG VERSION
 ENV OS "linux"
 ENV BIT "64"
 
-RUN echo "Installing curl..." && \
-    apt update && apt install -y curl && \
-    if [ x$VERSION = 'latest' ] ; then \
+RUN apk add --no-cache curl
+
+RUN VERSION=${VERSION:-latest} && \
+    if [ $VERSION = 'latest' ]; then \
       echo "Downloading latest version of Operator SDK from Github..." && \
       curl -sL https://api.github.com/repos/operator-framework/operator-sdk/releases |\
         grep browser_download |\
-        grep $OS |\
+        grep ${OS} |\
         cut -d '"' -f 4 |\
         grep operator-sdk |\
-        grep x86_$BIT-$OS |\
+        grep x86_${BIT}-${OS} |\
         grep -v .asc |\
         head -n 1 |\
         xargs curl -sOL; \
    else \
       echo "Downloading version $VERSION of Operator SDK from Github..." && \
       curl -sOL "https://github.com/operator-framework/operator-sdk/releases/download/v${VERSION}/operator-sdk-v${VERSION}-x86_${BIT}-${OS}-gnu"; \
    fi && \
-   cp ./operator-sdk-* /usr/local/bin/operator-sdk && rm -f ./operator-sdk && \
+   cp ./operator-sdk-* /usr/local/bin/operator-sdk && rm -f ./operator-sdk* && \
    chmod a+x /usr/local/bin/operator-sdk && \
-   rm -rf /var/lib/apt/lists/* /tmp/* && \
    mkdir -p /source
 
 WORKDIR /source

README.md

@@ -1,10 +1,17 @@
 # operator-sdk
-Run the [Kubernetes Operator SDK](https://github.com/operator-framework/operator-sdk) using Docker. This is especially useful in environments where 
-installing the binaries is not an option (e.g. in CI/CD pipelines).
+
+Run the [Kubernetes Operator SDK](https://github.com/operator-framework/operator-sdk) using Docker. This is especially 
+useful in environments where installing the binaries is not an option (e.g. in CI/CD pipelines). The `latest` version of
+this image will be the latest release of the *Operator SDK*.
 
 ## Usage
-Build a custom operator using the `operator-sdk` command:
+
+Before you start, you must have a Docker daemon running on the host machine. You can check this by using the command 
+`docker version`. In order to build a custom operator using the `operator-sdk` binary, use the following command:
 
 ```bash
-docker run --rm -v ${PWD}:/source build operator-image:operator-version
+docker run --rm -v ${PWD}:/source -v /var/run/docker.sock:/var/run/docker.sock --privileged boonen/operator-sdk:latest build operator-image:operator-version
 ```
+
+This command will mount the current working directory in `/source` and build the operator based on the source code in the
+working directory.