简单的dockerfile例子
这里先给一个简单的例子，用来说明基本的dockerfile的组成：
# Barebones Apache installation on Ubuntu
FROM ubuntu
MAINTAINER DockerFan version 1.0
ENV DEBIAN_FRONTEND noninteractive
ENV APACHE_RUN_USER www-data
ENV APACHE_RUN_GROUP www-data
ENV APACHE_LOG_DIR /var/log/apache2
ENV APACHE_LOCK_DIR /var/lock/apache2
ENV APACHE_PID_FILE /var/run/apache2.pid
RUN apt-get update && apt-get install -y apache2
EXPOSE 8080
CMD ["/usr/sbin/apache2ctl", "-D", "FOREGROUND"]
解释
Here’s what the instructions do:
- FROM is always your first instruction, because it names the base image you’re building your new image from.
-
MAINTAINER is the creator of the Dockerfile.
-
ENV sets environment variables, in the form ENV [key] [value]. This assigns a single value to the key, as in our example Dockerfile. The value can be any string, including spaces and punctuation, so you can configure values like IP addresses, URLs, and passphrases. Note that when you set DEBIAN_FRONTEND noninteractive (for an unattended installation) in your Dockerfile there is no equals sign, as there is when you script a standard Debian or Ubuntu installation with export DEBIAN_FRONTEND=noninteractive.
-
There are multiple instructions for setting environment variables: ADD, COPY, ENV, EXPOSE, LABEL, USER, WORKDIR, VOLUME, STOPSIGNAL, and ONBUILD.
-
RUN executes commands. The example above, RUN apt-get update && apt-get install -y apache2, demonstrates two important steps. It is a good practice to use apt-get update && apt-get install foo together to ensure that an updated packaged will be installed. Docker makes generous use of caching, so this prevents a cached packaged from being installed. If you’re sure your cached packages are fresh enough then it’s not necessary, and will save you some download time. apt-get install -y must be used together with ENV DEBIAN_FRONTEND noninteractive; it means answer Yes to all prompts and run non-interactively.
-
EXPOSE defines which ports you want open at runtime, in a space-delimited list.
-
CMD can be used only once in your Dockerfile. If you have more than one, only the last one will run. The preferred syntax is CMD [“executable”,”param1″,”param2″]. The parameters are optional and comma-separated if you have more than one.
完整的LAMP dockerfile
# Ubuntu LAMP stack with Apache, MariaDB, PHP, and SSL
FROM ubuntu
MAINTAINER DockerFan version 1.0
ENV DEBIAN_FRONTEND noninteractive
ENV APACHE_RUN_USER www-data
ENV APACHE_RUN_GROUP www-data
ENV APACHE_LOG_DIR /var/log/apache2
ENV APACHE_LOCK_DIR /var/lock/apache2
ENV APACHE_PID_FILE /var/run/apache2.pid
# Install Apache, SSL, PHP, and some PHP modules
RUN apt-get update && apt-get install -y apache2
openssl
php5
php5-cli
php5-apcu
# Install MariaDB and set default root password
RUN echo 'mariadb-server mariadb-server/root_password password mypassword' | debconf-set-selections
RUN echo 'mariadb-server mariadb-server/root_password_again password mypassword' | debconf-set-selections
RUN apt-get install mariadb-server -y
# Disable the default Apache site config
# Install your site's Apache configuration and activate SSL
ADD my_apache.conf /etc/apache2/sites-available/
RUN a2dissite 000-default
RUN a2ensite my_apache
RUN a2enmod ssl
# Remove APT files
RUN apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
EXPOSE 443 8080
CMD ["/usr/sbin/apache2ctl", "-D", "FOREGROUND"]
The section that installs Apache, SSL, and PHP shows the proper Docker way to install multiple packages at once, with each package on its own line ending in a backslash. The MariaDB installation sections shows how to use debconf to automatically set the root DB password.
You will need your own Apache virtual host configuration file, and it should be in the same directory as your Dockerfile. Use the ADD instruction to build it into your image. I like to do a little housecleaning to keep my image as small as possible by running apt-get clean, and removing temp files.
Since we are using SSL, we’ll need port 443 available. On a production system, you would probably want only port 443 enabled, and use mod_rewrite to automatically redirect HTTP requests to HTTPS.