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Docker Basics

Docker commands

https://docs.docker.com/engine/reference/commandline

Images

docker search nmap

Pull image

docker pull uzyexe/nmap

Run image:

docker run -it uzyexe/nmap --help
docker run -i -d --name myubuntu ubuntu
  • -d for running in the backgound
  • –interactive or -i argument keep the container running

Check history in images

docker image history image-name

Containers

Run a command in a running container

docker exec myubuntu whoami

spawn a shell in the container

docker exec -it myubuntu bash

List containers

docker ps -a

Show the running processes of a container

docker top myubuntu

Check logs in the container

docker logs CONTAINER_ID

Manage Data In Docker

Docker volumes

create volume

docker volume create data
/# ls /var/lib/docker/volumes/
data  metadata.db

run a container to use data volumes

docker run --name ubuntu -d -v data:/opt -it ubuntu:18.04

Bind mounts

docker run --name ubuntu -d -v /opt:/opt -it ubuntu:18.04

tmpfs mounts

https://docs.docker.com/storage/tmpfs/

Docker Registry

Deploy local registry

https://docs.docker.com/registry/deploying/

docker run -d -p 5000:5000 --restart=always --name registry registry:2

Store the images

add the image name with the registry url as a prefix

docker tag ubuntu:1.0 localhost:5000/ubuntu:1.0

push the image to the docker registry

docker push localhost:5000/ubuntu:1.0

check images on the registy

curl localhost:5000/v2/_catalog

Docker Networking

Basic commands

See available networks

docker network ls
docker network list

remove

docker network rm mynetwork
Network Descriptions
bridge This is the default network driver when you don’t specify a driver to the containers. Containers on the same bridged network can speak to each other, but are isolated from containers on other bridged networks. All containers can access the external network through NAT
host The containers use the host’s networking directly, while retaining separation on storage and processing. Ports exposed by the container are exposed on the external network using the host’s IP address
macvlan When creating a macvlan, you assign a parent network device (e.g. “eth0”). Each container on the macvlan network will receive its own MAC address on the network that eth0 is connected to. Each container has full network access. Warning: when misconfigured, you may overrun the network with too many MACs, or you may duplicate IP addresses
none networking is disabled with this network driver, containers cannot communicate to each others, nor with the external network

Bridge config

https://blog.oddbit.com/post/2018-03-12-using-docker-macvlan-networks/

Create new and view detail

docker network create mynetwork
docker network create --subnet 192.10.1.0/16 app
docker inspect mynetwork

attach container using mynetwork

docker run -d --name ubuntu --network mynetwork -it ubuntu:18.04

connect to running container

docker network connect app ubuntu

macvlan config

create

docker network create --driver macvlan mymacvlan

attach container using mymacvlan

docker run -d --name ubuntu --network mymacvlan -it ubuntu:18.04

detail vlan for container

docker inspect ubuntu -f "{{json .NetworkSettings.Networks }}" | jq

https://docs.docker.com/network/macvlan/

none config

create

docker run -d --name ubuntu --network=none -it ubuntu:18.04

Create Docker Image

Dockerfile

# FROM python base image
FROM ubuntu:18.04

# COPY startup script
COPY . /app

WORKDIR /app

RUN apt update && apt install nginx -y
RUN apk add --no-cache gawk sed bash grep bc coreutils

# EXPOSE port 8080 for communication to/from server
EXPOSE 8080

ENTRYPOINT ["/bin/bash", "-c"]
# CMD specifcies the command to execute container starts running.
CMD ["/app/run_app_docker.sh"]
Syntax Description
FROM: Creates a layer from Docker Image. Specifies the base image to use.
COPY: Copies the files from the local directory to the docker image on a specific location.
ADD: Similar to COPY but supports file download (HTTP), auto extracting compressed file(s), and replacing the existing file to a specific location if needed forcefully.
RUN: Run OS command (just like you would do on a terminal) but only executes it during the image creation process.
ENTRYPOINT: Run a command as the default command when the container starts. Its the entrypoint to the utility/command.
CMD: Command to run when a container starts or arguments to ENTRYPOINT if specified.

https://goinbigdata.com/docker-run-vs-cmd-vs-entrypoint/

sleep infinity tells the container to keep the process alive.

FROM ubuntu:18.04

RUN apt update && apt install nginx -y

CMD ["/bin/bash", "-c" , "service nginx start; sleep infinity"]

Build Image

https://docs.docker.com/engine/reference/builder/

docker build -f /path/to/a/Dockerfile -t shykes/myapp .
  • -f flag with docker build to point to a Dockerfile anywhere in your file system
  • -t tag at which to save the new image

Docker Compose

Introduction

Dockerfile: handle 1 container

Docker Compose: handle multiple containers using a single file called docker-compose.yml

version: "3"

services:
  ubuntu:
    image: ubuntu:18.04
    stdin_open: true        # the same way like docker run -i

Run

docker-compose up -d

Compose file

version: "3"

services:
  web:
    image: nginx
    container_name: webserver       # name of container
    ports:
     - "80:80"                      # similar to docker run -p 80:80
    environment:
     - NGINX_HOST=example.com       # similar to docker run -e VAR=value
    volumes:
     - ./:/var/www/html/app             # ./ means a bind mounts
     - image_data:/var/www/html/images  # image_data means use docker volume

volumes:
  image_data:                       # similar to docker volume create
Syntax Descriptions
version Version of compose file format to use
image Specify the image to run
container_name Specify a custom container name, rather than a default name
ports Expose port(s), similar to docker run -p argument
environment Add environment variables into the container by defining a key-value pair
volumes Volumes to save our data persistently using various options type like bind or volumes