This could be maybe a trivial question but reading docs for ARG and ENV doesn't put things clear to me.
I am building a PHP-FPM container and I want to give the ability for enable/disable some extensions on user needs.
Would be great if this could be done in the Dockerfile by adding conditionals and passing flags on the build command perhaps but AFAIK is not supported.
In my case and my personal approach is to run a small script when container starts, something like the following:
#!/bin/sh
set -e
RESTART="false"
# This script will be placed in /config/init/ and run when container starts.
if [ "$INSTALL_XDEBUG" == "true" ]; then
printf "\nInstalling Xdebug ...\n"
yum install -y php71-php-pecl-xdebug
RESTART="true"
fi
...
if [ "$RESTART" == "true" ]; then
printf "\nRestarting php-fpm ...\n"
supervisorctl restart php-fpm
fi
exec "$@"
This is how my Dockerfile
looks like:
FROM reynierpm/centos7-supervisor
ENV TERM=xterm \
PATH="/root/.composer/vendor/bin:${PATH}" \
INSTALL_COMPOSER="false" \
COMPOSER_ALLOW_SUPERUSER=1 \
COMPOSER_ALLOW_XDEBUG=1 \
COMPOSER_DISABLE_XDEBUG_WARN=1 \
COMPOSER_HOME="/root/.composer" \
COMPOSER_CACHE_DIR="/root/.composer/cache" \
SYMFONY_INSTALLER="false" \
SYMFONY_PROJECT="false" \
INSTALL_XDEBUG="false" \
INSTALL_MONGO="false" \
INSTALL_REDIS="false" \
INSTALL_HTTP_REQUEST="false" \
INSTALL_UPLOAD_PROGRESS="false" \
INSTALL_XATTR="false"
RUN yum install -y https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm \
https://rpms.remirepo.net/enterprise/remi-release-7.rpm
RUN yum install -y \
yum-utils \
git \
zip \
unzip \
nano \
wget \
php71-php-fpm \
php71-php-cli \
php71-php-common \
php71-php-gd \
php71-php-intl \
php71-php-json \
php71-php-mbstring \
php71-php-mcrypt \
php71-php-mysqlnd \
php71-php-pdo \
php71-php-pear \
php71-php-xml \
php71-pecl-apcu \
php71-php-pecl-apfd \
php71-php-pecl-memcache \
php71-php-pecl-memcached \
php71-php-pecl-zip && \
yum clean all && rm -rf /tmp/yum*
RUN ln -sfF /opt/remi/php71/enable /etc/profile.d/php71-paths.sh && \
ln -sfF /opt/remi/php71/root/usr/bin/{pear,pecl,phar,php,php-cgi,phpize} /usr/local/bin/. && \
mv -f /etc/opt/remi/php71/php.ini /etc/php.ini && \
ln -s /etc/php.ini /etc/opt/remi/php71/php.ini && \
rm -rf /etc/php.d && \
mv /etc/opt/remi/php71/php.d /etc/. && \
ln -s /etc/php.d /etc/opt/remi/php71/php.d
COPY container-files /
RUN chmod +x /config/bootstrap.sh
WORKDIR /data/www
EXPOSE 9001
Here is the whole repository if you need to take a deep look in order to understand how I am doing things
Currently this is working but ... If I want to add let's say 20 (a random number) of extensions or any other feature that can be enable|disable then I will end with 20 non necessary ENV
(because Dockerfile doesn't support .env files) definition whose only purpose would be set this flag for let the script knows what to do then ...
ENV
for this purpose? I am open to ideas if you have a different approach for achieve this please let me know about it
From Dockerfile reference:
The
ARG
instruction defines a variable that users can pass at build-time to the builder with the docker build command using the--build-arg <varname>=<value>
flag.The
ENV
instruction sets the environment variable<key>
to the value<value>
.
The environment variables set usingENV
will persist when a container is run from the resulting image.
So if you need build-time customization, ARG
is your best choice.
If you need run-time customization (to run the same image with different settings), ENV
is well-suited.
If I want to add let's say 20 (a random number) of extensions or any other feature that can be enable|disable
Given the number of combinations involved, using ENV
to set those features at runtime is best here.
But you can combine both by:
ARG
ARG
as an ENV
That is, with a Dockerfile including:
ARG var
ENV var=${var}
You can then either build an image with a specific var
value at build-time (docker build --build-arg var=xxx
), or run a container with a specific runtime value (docker run -e var=yyy
)