Using APK for Alpine Linux with Docker

Some quick tips on how to use apk for Alpine Linux in a Docker environment. Some common use cases might be to install command line tools you will use in scripts, or to compile a PHP extension. In the former you will often be able to access a binary, and not need to worry about polluting much of your Docker layer with extra files. When you need to compile something however – like a PHP extension – you may need several build tools as well as libraries that you don’t need to keep around after you compile the module.

This first example is common for installing command line tools:

RUN apk add --no-cache --update \
  bash curl findutils sed sudo

The next example shows how to compile PHP modules and remove their dependencies after compilation.

RUN set -xe; \
    apk add --no-cache --virtual .build-deps $PHPIZE_DEPS \
      # build tools
      autoconf g++ gcc make \
      # lib tools
      bzip2-dev freetype-dev gettext-dev icu-dev imagemagick-dev libintl libjpeg-turbo-dev \
      #  libmcrypt-dev 
      libpng-dev libxslt-dev libzip-dev \
      ; \
    docker-php-ext-configure \
      gd --with-freetype-dir=/usr/include/ --with-jpeg-dir=/usr/include/ --with-png-dir=/usr/include/ \
      ; \
    docker-php-ext-install -j$(nproc) \
      bcmath bz2 calendar exif gettext gd intl mysqli opcache pcntl pdo_mysql soap xsl zip \
      ; \
    pecl channel-update pecl.php.net && \
    pecl install -o -f \
      redis \
      ; \
    docker-php-ext-enable \
      redis \
      ; \
    runDeps="$( \
      scanelf --needed --nobanner --format '%n#p' --recursive /usr/local/lib/php/extensions \
        | tr ',' '\n' \
        | sort -u \
        | awk 'system("[ -e /usr/local/lib/" $1 " ]") == 0 { next } { print "so:" $1 }' \
    )"; \
      apk add --virtual .phpexts-rundeps $runDeps; \
      apk del .build-deps