Docker Operations Log (Part 2)

Continuing from Docker Operations Log (Part 1)

Basic Docker Usage

Deleting a Container

Remember to stop the container using stop before deleting it.

docker rm CONTAINER_NAME

Or

docker rm CONTAINER_ID

After deletion, you can use

docker ps -a

to confirm if the container has disappeared.

Creating an Image from a Previously Exported Container

If you previously exported a container as c_test.tar, you can use it to create a new image:

cat c_test.tar | docker import - ubuntu_test_repo:1.0

ubuntu_test_repo is the repository name, and 1.0 is the tag.
You can use

docker images

to list and check it.
Once you have an image, you can create new containers from it.

Deleting an Image

If I use

docker images

and the listed images are:

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
aaa                 2.0                 b30c39fffb75        4 seconds ago       64.2MB
aaa                 1.0                 6b8046192d83        8 seconds ago       64.2MB
ubuntu_test_repo    1.0                 864c36a752c3        5 hours ago         64.2MB
ubuntu              latest              549b9b86cb8d        2 weeks ago         1.84kB
hello-world         latest              fce289e99eb9        12 months ago       1.84kB

To delete the image with repository name aaa and tag 1.0:

docker rmi aaa:1.0

This will work.
All containers using this image must be rm’d first.

Dockerfile

A Dockerfile is a file that allows users to create images in a simpler way.

It is divided into four parts:

• Image
• Maintainer (who is responsible for this Dockerfile)
• Operation commands
• Command to run when the container starts

Here’s an Nginx example:

# This is how to comment in a Dockerfile

# Image
FROM ubuntu

# Maintainer
MAINTAINER user user@example.com

# Operation commands
RUN apt-get update \
&& apt-get upgrade -y \
&& apt-get install -y nginx

# Container Start Command
CMD ["nginx", "-g", "daemon off;"]

Building an Image

You can use docker build to create an image.

If the Nginx Dockerfile mentioned above is located at /tmp/d_file and named test_d_file, to build it into an image and tag it as test-nginx-img/1.0:

docker build -t test-nginx-img/1.0 -f /tmp/d_file/test_d_file .

After building, check with docker images:

REPOSITORY           TAG                 IMAGE ID            CREATED             SIZE
test-nginx-img/1.0   latest              7293588d00a9        27 seconds ago      152MB

Reference

Docker docs