Docker Cookbook

1.13 Creating, Starting, Stopping, and Removing Containers | 23

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$ docker restart a842945e2414
a842945e2414
$ docker ps
CONTAINER ID IMAGE COMMAND ... NAMES
a842945e2414 python:2.7 "python -m SimpleHTT ... fervent_hodgkin
$ docker kill a842945e2414
a842945e2414
$ docker rm a842945e2414
a842945e2414
$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
If you have a lot of stopped containers that you would like to
remove, use a subshell to do it in one command. The 
-q
option of
docker ps
will return only the containers’ IDs:
$ docker rm $(docker ps -a -q)
1.14 Building a Docker Image with a Dockerfile
Problem
You understand how to download images from a publicly available Docker registry
but you would like to build your own Docker images.
Solution
Use a Dockerfile. A 
Dockerfile
is a text file that describes the steps that Docker needs
to take to prepare an image—including installing packages, creating directories, and
defining environment variables, among other things. In 
Chapter 2
, we will expand
much further about Dockerfiles and image creation. This recipe covers the basic con‐
cept of building an image.
As a toy example, let’s say you want to create an image based on the 
busybox
image
but that you want to define an environment variable. The 
busybox
image is a Docker
image that contains the 
busybox
 binary, which combines most Unix utilities in a sin‐
gle binary. Create the following text file named 
Dockerfile
in an empty working direc‐
tory:
FROM busybox
ENV foo=bar
Then to build a new image called 
busybox2
, you use the 
docker build
command like
so:
$ docker build -t busybox2 .
Sending build context to Docker daemon 2.048 kB
Step 0 : FROM busybox