Using Supervisor with Docker
Note: - If you don't like sudo then see Giving non-root access
Traditionally a Docker container runs a single process when it is
launched, for example an Apache daemon or a SSH server daemon. Often
though you want to run more than one process in a container. There are a
number of ways you can achieve this ranging from using a simple Bash
script as the value of your container's
CMD instruction to installing
a process management tool.
In this example we're going to make use of the process management tool, Supervisor, to manage multiple processes in our container. Using Supervisor allows us to better control, manage, and restart the processes we want to run. To demonstrate this we're going to install and manage both an SSH daemon and an Apache daemon.
Creating a Dockerfile
Let's start by creating a basic
Dockerfile for our
FROM ubuntu:13.04 MAINTAINER firstname.lastname@example.org RUN echo "deb http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list RUN apt-get update RUN apt-get upgrade -y
We can now install our SSH and Apache daemons as well as Supervisor in our container.
RUN apt-get install -y openssh-server apache2 supervisor RUN mkdir -p /var/run/sshd RUN mkdir -p /var/log/supervisor
Here we're installing the
(which provides the Supervisor daemon) packages. We're also creating two
new directories that are needed to run our SSH daemon and Supervisor.
Adding Supervisor's configuration file
Now let's add a configuration file for Supervisor. The default file is
supervisord.conf and is located in
ADD supervisord.conf /etc/supervisor/conf.d/supervisord.conf
Let's see what is inside our
[supervisord] nodaemon=true [program:sshd] command=/usr/sbin/sshd -D [program:apache2] command=/bin/bash -c "source /etc/apache2/envvars && exec /usr/sbin/apache2 -DFOREGROUND"
supervisord.conf configuration file contains
directives that configure Supervisor and the processes it manages. The
[supervisord] provides configuration
for Supervisor itself. We're using one directive,
which tells Supervisor to run interactively rather than
The next two blocks manage the services we wish to control. Each block
controls a separate process. The blocks contain a single directive,
command, which specifies what command to run to
start each process.
Exposing ports and running Supervisor
Now let's finish our
Dockerfile by exposing some
required ports and specifying the
to start Supervisor when our container launches.
EXPOSE 22 80 CMD ["/usr/bin/supervisord"]
Here We've exposed ports 22 and 80 on the container and we're running
/usr/bin/supervisord binary when the container
Building our image
We can now build our new image.
$ sudo docker build -t <yourname>/supervisord .
Running our Supervisor container
Once We've got a built image we can launch a container from it.
$ sudo docker run -p 22 -p 80 -t -i <yourname>/supervisord 2013-11-25 18:53:22,312 CRIT Supervisor running as root (no user in config file) 2013-11-25 18:53:22,312 WARN Included extra file "/etc/supervisor/conf.d/supervisord.conf" during parsing 2013-11-25 18:53:22,342 INFO supervisord started with pid 1 2013-11-25 18:53:23,346 INFO spawned: 'sshd' with pid 6 2013-11-25 18:53:23,349 INFO spawned: 'apache2' with pid 7 . . .
We've launched a new container interactively using the
docker run command.
That container has run Supervisor and launched the SSH and Apache daemons with
it. We've specified the
-p flag to expose ports 22 and 80. From here we can
now identify the exposed ports and connect to one or both of the SSH and Apache