Adding GD support to a Docker image

I had to create a new docker container to emulate a site we have working on older versions of MySQL and PHP (don’t ask, long story).

The CMS was failing spectacularly. After suspecting memory issues and other esoteric settings I realized it was much more basic: there was no GD support in this container and the plugin that manipulated images was dying without generating any error messages (thanks for that, plugin developer).

Long story short, here’s my Dockerfile to get GD support working. This was one of those “look at a bunch of stack exchange answers and kind of merge them together” solutions so I’m not 100% sure how universally it will work. The bits in red are what I added for GD support. Frankly I’m not sure about that RUN NUMPROC line… I need to research that more because I honestly don’t understand what it is doing.

EDIT: OK the -j parameter passed to docker-php-ext-install is the number of make jobs that can run concurrently (in order to speed up compilation). The RUN NUMPROC line is looking at how many CPUs you have and telling make it can run that many jobs at the same time.

Edit 2: As of April 2, 2019 I started running into problems where my docker build who throw up errors like this:
Failed to fetch http://deb.debian.org/debian/dists/jessie-updates/main/binary-amd64/Packages

Apparently Debian “Jessie” updates have been moved to the archives. The solution is to tweak the sources list, new line added in green
Solution comes from https://github.com/debuerreotype/docker-debian-artifacts/issues/66#issuecomment-476616579

FROM php:5.6.38-apache

COPY 000-default.conf /etc/apache2/sites-available/000-default.conf
COPY php.ini /usr/local/etc/php/php.ini
RUN mkdir -p /etc/apache2/ssl/
COPY ./ssl.crt /etc/apache2/ssl/ssl.crt
COPY ./ssl.key /etc/apache2/ssl/ssl.key
RUN mkdir -p /var/run/apache2/

RUN sed -i '/jessie-updates/d' /etc/apt/sources.list # Now archived

RUN apt-get update -y && apt-get install -y zlib1g-dev libjpeg62-turbo libpng-dev libjpeg-dev

RUN docker-php-ext-configure gd \
--with-png-dir=/usr/lib/ \
--with-jpeg-dir=/usr/lib/ \
--with-gd

RUN NUMPROC=$(grep -c ^processor /proc/cpuinfo 2>/dev/null || 1) \
&& docker-php-ext-install -j${NUMPROC} gd

RUN docker-php-ext-install pdo_mysql
RUN docker-php-ext-install mysqli
RUN a2enmod rewrite
RUN a2enmod ssl

EXPOSE 80
EXPOSE 443

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