<!--[metadata]>
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title = "Dockerizing a Redis service"
description = "Installing and running an redis service"
keywords = ["docker, example, package installation, networking,  redis"]
[menu.main]
parent = "engine_dockerize"
+++
<![end-metadata]-->

# Dockerizing a Redis service

Very simple, no frills, Redis service attached to a web application
using a link.

## Create a Docker container for Redis

Firstly, we create a `Dockerfile` for our new Redis
image.

    FROM        ubuntu:14.04
    RUN         apt-get update && apt-get install -y redis-server
    EXPOSE      6379
    ENTRYPOINT  ["/usr/bin/redis-server"]

Next we build an image from our `Dockerfile`.
Replace `<your username>` with your own user name.

    $ docker build -t <your username>/redis .

## Run the service

Use the image we've just created and name your container `redis`.

Running the service with `-d` runs the container in detached mode, leaving
the container running in the background.

Importantly, we're not exposing any ports on our container. Instead
we're going to use a container link to provide access to our Redis
database.

    $ docker run --name redis -d <your username>/redis

## Create your web application container

Next we can create a container for our application. We're going to use
the `-link` flag to create a link to the `redis` container we've just
created with an alias of `db`. This will create a secure tunnel to the
`redis` container and expose the Redis instance running inside that
container to only this container.

    $ docker run --link redis:db -i -t ubuntu:14.04 /bin/bash

Once inside our freshly created container we need to install Redis to
get the `redis-cli` binary to test our connection.

    $ sudo apt-get update
    $ sudo apt-get install redis-server
    $ sudo service redis-server stop

As we've used the `--link redis:db` option, Docker
has created some environment variables in our web application container.

    $ env | grep DB_

    # Should return something similar to this with your values
    DB_NAME=/violet_wolf/db
    DB_PORT_6379_TCP_PORT=6379
    DB_PORT=tcp://172.17.0.33:6379
    DB_PORT_6379_TCP=tcp://172.17.0.33:6379
    DB_PORT_6379_TCP_ADDR=172.17.0.33
    DB_PORT_6379_TCP_PROTO=tcp

We can see that we've got a small list of environment variables prefixed
with `DB`. The `DB` comes from the link alias specified when we launched
the container. Let's use the `DB_PORT_6379_TCP_ADDR` variable to connect to
our Redis container.

    $ redis-cli -h $DB_PORT_6379_TCP_ADDR
    $ redis 172.17.0.33:6379>
    $ redis 172.17.0.33:6379> set docker awesome
    OK
    $ redis 172.17.0.33:6379> get docker
    "awesome"
    $ redis 172.17.0.33:6379> exit

We could easily use this or other environment variables in our web
application to make a connection to our `redis`
container.
