05 - Docker - Containers

Docker - Containers

- Container is operating system-level virtualization ( Linux Kernal )

Allow for multiple isolated user-space instances called containers
They share a single kernel
Can be added or removed any times

- Containers consist of a self-contained Linux file system

Can be from any Linux distribution which is compatible with the host kernel
Usually contain a single application such as a server

- Operating

Is often used in Cloud Computing

Docker Architecture

Docker is available in two editions:

Community Edition (CE) - open-source
Enterprise Edition (EE)

Docker uses a client-server architecture

Client

REST API ( the primary user interface which communicates )

Over HTTP
Over local Unix Socket

Docker CLI

docker build
docker pull
docker run

Servers (Docker_Host)

Is the Docker daemon
Responsible for building, running, and distributing containers

Docker daemon
Container
Images

Registry (docker.io , DockerHub)

Responsible for the storage, management, and delivery of Docker images

Docker Hub
Private
Other Vendor

Docker Images and Containers

Docker images are read-only templates

Foundation is a simplified version of the Linux operating system
Changes to foundation, such as application installations added to the Image
Images are the templates or build commands for Docker

Docker containers are running environments

Has OS, environment, program, network, etc.
Runs (probably one) application
All required software contained in image
Can have boot-up configuration
They can be run, started, stopped, and deleted

Docker Images

Docker images are built in layers

Each layer is a file system
The layers are combined in a union file system to make a single image
o Images are the build component of Docker

Images start from a base image

Foundation is usually a specifically prepared Linux operating system

Custom base images can also be created

Docker Image is then built by adding layers:

Interactively
Defined in a directive file called a “Dockerfile”

Docker Containers

The docker ‘run’ command starts a container based on a named Docker Image

Docker first looks for a local copy of the image

If it does not exist it is pulled from a Docker Registry

The default Registry is the Docker Hub Registry

A new container is created using the file system from the image
A read-write layer is added to the top of the file system
A network interface is created and an IP address is assigned from a pool
Standard input, output, and error streams are connected
A specified application is executed

Docker container appears as a child of the daemon process, ms are connected

Docker Registries

A Docker registry stores Docker images
Docker Hub is a public registry that anyone can use, and Docker is configured to look for images on Docker Hub by default
You can even run your own private registry
When you use the docker pull or docker run commands, the required images are pulled from your configured registry
When you use the docker push command, your image is pushed to your configured registry

Docker Lab

$ vagrant ssh

$ sudo su -
$ hostnamectl set-hostname docker.unixcloudfusion.in

$ cat /etc/hosts
192.168.33.20 docker.unixcloudfusion.in

**** Download Docker

$ wget get.docker.com

$ cat index.html
$ rm -f index.html

**** Installing of docker c
$ curl -fsSL get.docker.com | sh

$ systemctl status docker

$ systemctl start docker
$ systemctl enable docker

$ usermod -aG docker vagrant
$ su vagrant

docker info

docker version

docker help

docker container ls

docker ps -a

docker run hello-world

** hub.docker.com -> docker repository

docker ps -a

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

34bf1f33b482 hello-world "/hello" 5 minutes ago Exited (0) 5 minutes ago wizardly_spence

** Search images from registry ( docker hub)

docker search ubuntu

** Pull an image from a registry

docker pull centos:lastest

3c72a8ed6814: Pull complete

Digest: sha256:76d24f3ba3317fa945743bb3746fbaf3a0b752f10b10376960de01da70685fbd

Status: Downloaded newer image for centos:latest

docker.io/library/centos:latest

docker run centos:latest whoami

root

docker run centos:latest w

docker run centos:latest date

** Interactive mode

** -i --> interactive keeps STDIN open

** -t --> tty allocate a pseduo TTY

docker run -i -t centos:latest /bin/bash

[root@6ee6f22ebdae /]# cat /etc/hosts

127.0.0.1 localhost

::1 localhost ip6-localhost ip6-loopback

fe00::0 ip6-localnet

ff00::0 ip6-mcastprefix

ff02::1 ip6-allnodes

ff02::2 ip6-allrouters

172.17.0.2 6ee6f22ebdae

docker stats

docker run -it --name centosvm1 centos:latest /bin//bash

** Stop a running container through SIGTERM
docker stop centosvm1

** Delete an image

docker rm centosvm1

docker attach centosvm1 ** not recommended way to use attach docker

docker run -it --name centosvm2 centos:latest /bin/bash

docker pause centosvm2

docker unpuase centosvm2

docker restart ventosvm2

** Stop a running container through SIGKILL

docker kill centosvm2

** List all images that are locally stored with the Docker engine

docker images

[root@localhost ~]# docker images

REPOSITORY TAG IMAGE ID CREATED SIZE

centos latest 0d120b6ccaa8 3 months ago 215MB

hello-world latest bf756fb1ae65 11 months ago 13.3kB

** Delete an image from the local image store

docker rmi hello-world

[root@localhost ~]# docker rmi hello-world

Error response from daemon: conflict: unable to remove repository reference "hello-world" (must force) - container 34bf1f33b482 is using its referenced image bf756fb1ae65

** Failed .. first, remove hello container

docker rm 34bf1f33b482

docker rmi hello-world

[root@localhost ~]# docker rmi hello-world

Untagged: hello-world:latest

Untagged: hello-world@sha256:e7c70bb24b462baa86c102610182e3efcb12a04854e8c582838d92970a09f323

Deleted: sha256:bf756fb1ae65adf866bd8c456593cd24beb6a0a061dedf42b26a993176745f6b

docker run -it --name centosvm3 centos:latest

yum install -y which

yum install -y net-tools

docker diff centosvm3 ** difference after the base image of centos

docker commit centosvm3 centos-net

docker run -it --name custom-centos centos-net:latest

docker inspect centos-net

docker volume help

** Exec container

docker exec -it centosvm3 /bin/bash

** Access containir again

docker attach centosvm3

** Delete all container which stops state

docker container prune

** Delete all images

docker images prune -a

** Save Images into iso file

docker images

docker save -o mycentos.iso centosvm3

** Load iso file into image in any other environment ( like usb and share folder )

docker load -i mycentos.iso

** How to Automate the process to create web server image and deploy container

mkdir nginx

cd nginx

vi index.html
<h1>Hello World</h1>

vi Dockerfile

FROM centos:latest

MAINTAINER ali.muhammad@yahoo.com

RUN yum install -y nginx

COPY index.html /usr/share/nginx/html

ENV JAVA_HOME=/usr/java/latest

EXPOSE 80

CMD ["ngix", "-g", "daemon off;"]

CMD ["echo", "Image created"]

docker build -t webserver:v1 .

docker images

docker run -d -p 80:80 webserver:v1 ** container detach mode

To exit a container and to leave it running use : CTRL-p CTRL-q

docker logs -tail 100 webserver:v1

** Create own registry

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

docker pull ubuntu:16.04 ** download from docker hub

docker images

docker tag ubuntu:16.04 localhost:5000/ubuntu-nonprod

docker push localhost:5000/ubuntu-nonprod

docker rmi ubuntu:16.04

docker rmi localhost:5000/ubuntu-nonprod

docker pull localhost:5000/ubuntu-nonprod

** Open site hub.docker.com and create own account

Docker ID : mali1969

Email:

Password:

docker login --username=mali1969

Password :

docker tag webserver:v1 mali1969/ifra-automation:webserver-nginx-image

docker push mali1969/infra-automation:webserver-nginx-image

DOCKER NETWORKING

Docker Container Networking

1. Default

- Bridge

- Host

- None

2. User-defined

docker network ls

NETWORK ID NAME DRIVER SCOPE

7d4acdf70879 bridge bridge local

58a93505bcec host host local

41d8819ffdeb none null local

docker network inspect bridge

[

{

"Name": "bridge",

"Id": "7d4acdf70879132a57d0c0ac0d6e2e51754f85165d151f5481ed3a3cb52f8116",

"Created": "2020-12-12T02:08:52.657934281Z",

"Scope": "local",

"Driver": "bridge",

"EnableIPv6": false,

"IPAM": {

"Driver": "default",

"Options": null,

"Config": [

{

"Subnet": "172.17.0.0/16",

"Gateway": "172.17.0.1"

}

, , , , , ,

}

]

docker images

docker run -it webserver:v1

docker exec -it 2bc991329d75 bash

docker network create isolated_bridge

docker network ls

docker network inspect isloated_bridge

docker run -d --network isolated_bridge webserver:v1

docker network connect isloated_bridge trusting_hugle

docker network disconnect isolated_bridge trusting_hugle

docker stop <container id >

docker network rm isolated_bridge

docker network ls

DOCKER COMPOSE

sudo curl -L "https://github.com/docker/compose/releases/download/1.26.2/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose

sudo chmod +x /usr/local/bin/docker-compose

docker-compose -- version

docker-compose version 1.26.2, build eefe0d31

mkdir iac

cd iac

mkdir sshd ngnix mysql

vi docker-compose.yml

version: "2"

services:

sshd:

build: sshd

image: centos-sshd:latest

ports:

- "2222:22"

services:

nginx:

build: nginx

image: centos-nginx:latest

ports:

- "80:80"

services:

mysql:

build: mysql

image: centos-mysql:latest

ports:

- "3306:3306"

** only sshd

cd sshd

vi Dockerfile

FROM centos:lastest

RUN yum install -y openssh-server

RUN mkdir /var/run/sshd

RUN useradd -c "Student User" -m student

RUN echo "student:student" | chpasswd

RUN ssh-keygen -t rsa -f /etc/ssh/ssh_host_rsa_key -q -N ""

EXPOSE 22

CMD ["/usr/sbin/sshd", "-D"]

cd ..

docker-compose up -d

ssh -p 2222 student@192.168.33.15

docker-compose down

docker logs registry

ls -ld /usr/local/bin/docker-compose

chown root:docker /usr/local/bin/docker-compose

cat /etc/passwd | grep student

ls -l /run/nologin

rm /run/nologin

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