Docker Primer

This document will provide some quick info and commands to use once the Docker engine is installed on a machine.

Docker Hub

Visit the docker hub website to find docker images for use. Many of the images have documentation you can follow to get the container up and running.

Commands

Start docker

If docker is not running on Ubuntu use sudo service docker start

Download a container image

docker pull python3 will pull the latest version
docker pull python3:<tag> will pull the tagged version

List images on your machine

docker image ls

REPOSITORY         TAG                     IMAGE ID       CREATED         SIZE
google/cloud-sdk   latest                  2c1fab49df09   3 months ago    2.87GB
enzcheck           v1                      fc432184a3ab   5 months ago    415MB
amazonlinux        latest                  c1c1e5b1da96   6 months ago    143MB
openjdk            18.0.1.1-jdk-bullseye   73415276e8bd   16 months ago   667MB
python             latest                  a5d7930b60cc   22 months ago   917MB

Run container in interactive mode and leave container running

docker run -id --name python_dev python3
The --name parameter will be used to more easily reference the container. If no name is provided, a randominzed name is assisgned.

View all containers (running or not)

docker ps -a

CONTAINER ID   IMAGE                           COMMAND       CREATED         STATUS                      PORTS     NAMES
b74590299efe   google/cloud-sdk:latest         "bash"        3 months ago    Exited (0) 3 months ago               gcp
72330cfcfee4   amazonlinux                     "/bin/bash"   5 months ago    Exited (0) 3 months ago               aws
7740137bb556   openjdk:18.0.1.1-jdk-bullseye   "jshell"      16 months ago   Exited (0) 3 months ago               java_dev
61686bdb8d31   python                          "python3"     21 months ago   Exited (137) 27 hours ago             python_dev

Stop a container (does not erase data or configuration)

docker stop <name of container>
Example: docker stop python_dev

Start a stopped container

docker start python_dev

Remove a container (erases data and the container will have to be “run” again.)

docker rm python_dev or docker rm <CONTAINER ID>
CONTAINER ID can be viewed by using the docker ps -a command

Remove an image from your machine

docker rmi <IMAGE ID>
<IMAGE ID> can be found by running the docker image ls command

Running a container with port forwarding

You can expose the containers ports by specifiying the -p switch. This will allow you to reach the container from your local host. docker run -id --name apache_web -p 80 httpd

docker ps -a
CONTAINER ID   IMAGE       COMMAND              CREATED         STATUS            PORTS                                     NAMES
a1e73b6c80f5   httpd       "httpd-foreground"   7 seconds ago   Up 6 seconds      0.0.0.0:32768->80/tcp, :::32768->80/tcp   apache_web

Notice how the PORTS are shown.
You can now use a browser to go to http://localhost:32768 and reach the containers exposed port 80

If you like, you can also specify the local port.
docker run -id --name apache_web -p 8080:80 httpd

CONTAINER ID   IMAGE       COMMAND              CREATED          STATUS                      PORTS                                   NAMES
2d706ad8dff3   httpd       "httpd-foreground"   54 seconds ago   Up 53 seconds               0.0.0.0:8080->80/tcp, :::8080->80/tcp   apache_web

Notice that port 8080 now maps to port 80 on the container.
https://localhost:8080 to reach the web server on the container.

Advanced Docker

Create an isolated network

docker network create --driver bridge isolated_nw
docker run -id --network=isolated_nw --name=apache_web httpd

isolated_nw is the name of the network created earlier for sharing dns names name is the container name as well as the dns name inside the container

Map local directory to a directory on the container

docker run -id --name=apache_web -v ~/apache_files:/tmp/ httpd

The -v commmand (volume) will map your local home directory’s apache_files to the /tmp