Get started building PHP applications in docker containers on Red Hat Enterprise Linux in under 15 minutes.
In this tutorial, you will learn how to start building PHP applications in docker containers on Red Hat Enterprise Linux. In order to build and run containers you will first install docker on your Red Hat Enterprise Linux 7 system.
You will need a system running Red Hat Enterprise Linux 7 Server with a current Red Hat subscription that allows you to download software and updates from Red Hat. If you don’t have a Red Hat Enterprise Linux Server subscription, get Red Hat Enterprise Linux Developer Suite after registering at developers.redhat.com.
If you encounter difficulties at any point, see Troubleshooting and FAQ.
In this step, you will configure your system to build and run docker containers. In the process, you will add the necessary software repositories, then verify that your system has a current Red Hat subscription and is able to receive updates from Red Hat. Your system needs to be already registered with Red Hat.
First, you will enable two Red Hat software repositories that are disabled by default. Instructions are provided for both the command line (CLI) and graphical user interface (GUI).
Red Hat Subscription Manager can be started from the System Tools group of the Applications menu. Alternatively, you can start it from the command prompt by typing subscription-manager-gui.
Select Repositories from the System menu of the subscription manager. In the list of repositories, check the Enabled column for rhel-7-server-optional-rpms and rhel-7-server-extras-rpms. After clicking, it might take several seconds for the check mark to appear in the enabled column.
You can add or remove software repositories from the command line using the subscription-manager tool. Start a Terminal window if you don’t already have one open. Use su to become the root user. Use subscription-manager --list option to to view the available software repositories.
$ su -
# subscription-manager repos --listEnable the two additional repositories:
# subscription-manager repos --enable rhel-7-server-extras-rpms
# subscription-manager repos --enable rhel-7-server-optional-rpmsIn the next step you will:
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Update your system with any available software updates
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Install
dockerand a few additional rpms usingyum -
Configure the
dockerdaemon to start at boot time -
Start the
dockerdaemon
If you don’t have a root Terminal window open, start a Terminal window and become the root user with su.
Now download and install any available updates by running yum update. If updates are available, yum will list them and ask if it is OK to proceed.
$ su -
# yum updateInstall docker and necessary additional rpms:
# yum install docker device-mapper-libs device-mapper-event-libsEnable the docker daemon to start at boot time and start it now:
# systemctl enable docker.service
# systemctl start docker.serviceNow verify that the docker daemon is running:
# systemctl status docker.serviceYour system is now ready to build and run docker-formatted containers. If you encounter difficulties at any point, see Troubleshooting and FAQ.
This step will download and install PHP using a container from the Red Hat container registry. Installing the PHP container will make PHP available for use by other containers on your system. Because containers run in isolated environments, your host system will not be altered by the installation. You must use docker commands to use or view the container’s content.
The commands shown in this section can be used to download and install other containers, like application containers you build. Containers can specify that they require other containers to be installed, which can happen automatically. For example, you can specify in the Dockerfile that is used to describe and build your container that your application requires PHP. Then, when someone installs your container, their system will automatically download the required PHP container directly from the Red Hat container registry.
The PHP container is part of Red Hat Software Collections, which provides the latest development technologies for Red Hat Enterprise Linux. Access to the Red Hat Software Collections (RHSCL) is included with many Red Hat Enterprise Linux (RHEL) subscriptions. For more information about which subscriptions include RHSCL, see How to use Red Hat Software Collections (RHSCL) or Red Hat Developer Toolset (DTS).
If you don’t have a root Terminal window open, start a Terminal window and become the root user with su.
To download and install the PHP container, use the following command:
# docker pull registry.access.redhat.com/rhscl/php-56-rhel7
The docker images command shows the container image that was installed as well as any others that are on your system.
# docker images
Now start a bash shell inside the PHP container to have a look around. The shell prompt changes, which is an indication that you are typing at the shell inside the container. A ps -ef shows the only thing running inside the container is bash and ps. Type exit to leave the container’s bash shell.
# docker run -it rhscl/php-56-rhel7 /bin/bash
bash-4.2$ which php
/opt/rh/rh-php56/root/usr/bin/php
bash-4.2$ php -v
PHP 5.6.5 (cli) (built: Jun 10 2015 06:11:40)
bash-4.2$ pwd
/opt/app-root/src
bash-4.2$ ps -ef
UID PID PPID C STIME TTY TIME CMD
default 1 0 0 20:10 ? 00:00:00 /bin/bash
default 14 1 0 20:10 ? 00:00:00 ps -ef
bash-4.2$ exitThe prior docker run command created a container to run your command, keep any state, and isolate it from the rest of the system. You can view the list of running containers with docker ps. To see all of the containers that have been created, including those that have exited, use docker ps -a.
You can restart the container that was created above with docker start. Containers are referred to by name. Docker will automatically generate a name if you don’t provide one. Once the container has been restarted, docker attach will let you interact with the shell running inside of it. See the following example:
# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
ca29ebc027dd rhscl/php-56-rhel7 "container-entrypoint" About a minute ago Exited (0) 42 seconds ago determined_mayer
# docker start determined_mayer
pensive_lalande
# docker attach determined_mayerAt this point you are connected to the running shell inside the container. When you attach you won’t see the command prompt, so hit Enter to get it to print another one.
bash-4.2$ ps -ef
UID PID PPID C STIME TTY TIME CMD
default 1 0 0 20:11 ? 00:00:00 /bin/bash
default 12 1 0 20:12 ? 00:00:00 ps -ef
bash-4.2$ exitSince the only process in the container, bash, was told to exit the container will no longer be running. This can be verified with docker ps -a. Containers that are no longer needed can be cleaned up with docker rm <container-name>.
docker rm determined_mayer
To see what other containers are available in the Red Hat container registry, use one or more of the following searches:
# docker search registry.access.redhat.com/rhscl
# docker search registry.access.redhat.com/openshift3
# docker search registry.access.redhat.com/rhel
# docker search registry.access.redhat.com/jbossIf you need help, see Troubleshooting and FAQ.
In this step, you will create a tiny Hello World container that uses PHP as a web server. Once created, the container can be run on other systems that have docker installed. You will need to create several files in an empty directory using your favorite editor, including a Dockerfile that describes the container. You don’t need to be running under the root user to create the files, but you will need root privileges to run the docker commands.
First, create an empty directory, and then create a file named Dockerfile with the following contents, but change the MAINTAINER line to have your name and email address:
FROM rhscl/php-56-rhel7 MAINTAINER Your Name "[email protected]" EXPOSE 8000 COPY . /opt/app-root/src CMD /bin/bash -c 'php -S 0.0.0.0:8000'
Create the file index.php with the following contents:
<?php print "Hello, Red Hat Developers World from PHP " . PHP_VERSION . "\n"; ?>
Now build the container image using docker build. You will need to be root using su or sudo in the directory you created that contains Dockerfile and index.html.
# docker build -t myname/phpweb .
You can see the container image that was created using the following command:
# docker imagesNow run the container using docker run. The PHP http.server module will create a tiny web server that listens on port 8000 inside the container. The run command will map port 8000 on the host machine to port 8000 inside the container.
# docker run -d -p 8000:8000 myname/phpweb
The run command returns an ID for the container that you can ignore. To check that the container is running, use docker ps. Take note of the name that docker assigned to the running container.
# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
39392f89cbd2 myname/phpweb "container-entrypoint" 24 seconds ago Up 23 seconds 0.0.0.0:8000->8000/tcp, 8080/tcp grave_brownUse curl to access the PHP web server:
# curl http://localhost:8000/
Hello, Red Hat Developers World from PHP 5.6.5To view the logs from the running container use docker logs <container-name>:
# docker logs grave_brown
When you are done, stop the running container with the following command using the name obtained from running docker ps:
# docker stop grave_brownInformation about a container is available using docker inspect:
# docker inspect myname/phpweb
The output is a JSON structure that is easily readable. The Config section has details of the container’s runtime environment such as environment variables and default command. Note that much of the information in the container’s configuration was inherited from the parent container, which in this case is the PHP runtime container.
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Red Hat Enterprise Linux Atomic Host 7 Getting Started with Containers — This document covers working with and deploying containers on both Red Hat Enterprise Linux and Red Hat Enterprise Linux Atomic Host. It also provides information on orchestrating multi-container environments with kubernetes. See About Red Hat Enterprise Linux Atomic Host.
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Red Hat Enterprise Linux 7.2 Release Notes — includes information on recent updates to the container tools included in Red Hat Enterprise Linux and Atomic Host.
Atomic Host is specifically optimized for deploying Linux containers in environments like Infrastructure as a Service (IaaS) clouds. Atomic Host’s minimal footprint contains only the software needed to efficiently host containers. Atomic Host isn’t intended for software development activities as it doesn’t include development tools or a graphical user interface.
During software development it is suggested that you use Red Hat Enterprise Linux, which is suitable for many purposes including desktop and server installations. You can build and run containers on Red Hat Enterprise Linux, see Get Started with Docker Formatted Container Images on Red Hat Systems. The steps to build a container image that include your application can be automated with a Dockerfile.
After your application is packaged in a container you should test it on Atomic Host to ensure that it is ready for deployment. In addition to minimized footprint, production environments built for running containers benefit from Atomic Host’s enhanced security and atomic update and rollback capability.
Developers who are creating continuous integration/continuous delivery (CI/CD) environments will want to consider containers deployed on Atomic Host. This allows test environments to be quickly created while minimizing system resource requirements.
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My system is unable to download updates from Red Hat.
Your system must be registered with Red Hat using
subscription-manager register. You need to have a current Red Hat subscription or an evaluation. -
As a developer, how can I get a Red Hat Enterprise Linux subscription?
If you don’t have a Red Hat Enterprise Linux subscription, register at developers.redhat.com and then download Red Hat Enterprise Linux Developer Suite.
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How do I tell if there is a container image available that has a newer version of PHP?
How can I see what other container images are available?
I can’t find the container mentioned in this tutorial, how can I tell if the name changed?
To see what other containers are available in the Red Hat container registry, use one or more of the following searches:
# docker search registry.access.redhat.com/rhscl # docker search registry.access.redhat.com/openshift3 # docker search registry.access.redhat.com/rhel # docker search registry.access.redhat.com/jboss -
I can’t find the
dockerrpm.yumis unable to find thedockerrpm.When I try to install
docker,yumgives the error No package docker available.The
dockerrpm is in the rhel-7-server-extras-rpms software repository. It is only available for the server version of Red Hat Enterprise Linux. The rhel-7-server-extras-rpms repository is disabled by default. See the first step in this tutorial for information on enabling additional software repositories. -
Where can I learn more about delivering applications with Linux containers?
If you haven’t already joined the Red Hat Developers program, sign up at developers.redhat.com. Membership is free.
Recommended Practices for Container Development and many other container articles are available from the Red Hat Customer Portal.
If you are a Red Hat Technology Partner, visit the Container Zone at the Red Hat Connect for Technology Partners web site.