What Is Docker?
Docker describes themselves as "an open platform for developers and sysadmins to build, ship, and run distributed applications".
Docker allows you to run containers. A container is a sandboxed process running an application and its dependencies on the host operating system. The application inside the container considers itself to be the only process running on the machine while the machine can run multiple containers independently.
You can install Docker CE in different ways, depending on your needs:
Before you install Docker CE for the first time on a new host machine, you need to set up the Docker repository. Afterward, you can install and update Docker from the repository.
SET UP THE REPOSITORY
yum-utils provides the yum-config-manager utility, and device-mapper-persistent-data and lvm2 are required by the devicemapperstorage driver.$ sudo yum install -y yum-utils \ device-mapper-persistent-data \ lvm2$ sudo yum-config-manager \ --add-repo \ https://download.docker.com/linux/centos/docker-ce.repoOptional: Enable the nightly or test repositories.
These repositories are included in the docker.repo file above but are disabled by default. You can enable them alongside the stable repository. The following command enables the nightly repository.
$ sudo yum-config-manager --enable docker-ce-nightlyTo enable the test channel, run the following command:
$ sudo yum-config-manager --enable docker-ce-testYou can disable the nightly or test repository by running the yum-config-managercommand with the --disable flag. To re-enable it, use the --enable flag. The following command disables the nightly repository.
$ sudo yum-config-manager --disable docker-ce-nightlyINSTALL DOCKER CE
$ sudo yum install docker-ce docker-ce-cli containerd.io060A 61C5 1B55 8A7F 742B 77AA C52F EB6B 621E 9F35, and if so, accept it.yum install or yum update command always installs the highest possible version, which may not be appropriate for your stability needs.docker group is created, but no users are added to the group.$ yum list docker-ce --showduplicates | sort -rdocker-ce.x86_64 3:18.09.1-3.el7 docker-ce-stabledocker-ce.x86_64 3:18.09.0-3.el7 docker-ce-stabledocker-ce.x86_64 18.06.1.ce-3.el7 docker-ce-stabledocker-ce.x86_64 18.06.0.ce-3.el7 docker-ce-stable[Jenkins@instance-1 ~]$ docker info | grep -i root
Docker Root Dir: /var/lib/docker
[Jenkins@instance-1 ~]$ mkdir jenkins-data
[Jenkins@instance-1 ~]$ cd /home/Jenkins/jenkins-data/
[Jenkins@instance-1 jenkins-data]$ cat docker-compose.yml
version: '3'
services:
jenkins:
container_name: jenkins
image: jenkins/jenkins
ports:
- "8080:8080"
volumes:
- /home/Jenkins/jenkins-data/jenkins_home:/var/jenkins_home
networks:
- net
networks:
net:
[Jenkins@instance-1 jenkins-data]$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
jenkins/jenkins latest d6170c74e3ca 5 days ago
*******************IMPORTANT TIPS************
[Jenkins@instance-1 jenkins-data]$ sudo /usr/local/bin/docker-compose up -d
[Jenkins@instance-1 jenkins-data]$ sudo /usr/local/bin/docker-compose up -d
Recreating jenkins ... done
uid=1002(Jenkins) gid=1003(Jenkins) groups=1003(Jenkins),993(docker)
[Jenkins@instance-1 jenkins-data]$ sudo chown 1002:1002 jenkins_home -R ##give full access
http://35.243.159.3:8080/ -------->Jenkins URL
c:/etc/hosts --
35.243.159.3
common error
[Jenkins@instance-1 ~]$ sudo /usr/local/bin/docker-compose stop
ERROR:
Can't find a suitable configuration file in this directory or any
parent. Are you in the right directory?
Supported filenames: docker-compose.yml, docker-compose.yaml
[Jenkins@instance-1 ~]$ cd jenkins-data/
[Jenkins@instance-1 jenkins-data]$ sudo /usr/local/bin/docker-compose stop
Stopping jenkins ... done
Step 1 - Running A Container
The first task is to identify the name of the Docker Image which is configured to run Redis. With Docker, all containers are started based on a Docker Image. These images contain everything required to launch the process; the host doesn't require any configuration or dependencies.
Jane can find existing images at registry.hub.docker.com/or by using the command docker search <name>. For example, to find an image for Redis, you would use docker search redis.
Task
Using the search command, Jane has identified that the Redis Docker Image is called redis and wants to run the latest release. Because Redis is a database, Jane wants to run it as a background service while she continues to work.
To complete this step, launch a container in the background running an instance of Redis based on the official image.
The Docker CLI has a command called run which will start a container based on a Docker Image. The structure is docker run <options> <image-name>.
By default, Docker will run a command in the foreground. To run in the background, the option -d needs to be specified.
$ docker run -d redis
a2dd0786c7a26995aeb1406281c63929ebce53f5553de388cc711c805871998f
By default, Docker will run the latest version available. If a particular version was required, it could be specified as a tag, for example, version 3.2 would be docker run -d redis:3.2.
As this is the first time Paras is using the Redis image, it will be downloaded onto the Docker Host machine
Step 2 - Finding Running Containers
The launched container is running in the background, the docker ps command lists all running containers, the image used to start the container and uptime.
This command also displays the friendly name and ID that can be used to find out information about individual containers.
The command docker inspect <friendly-name|container-id>provides more details about a running container, such as IP address.
The command docker logs <friendly-name|container-id> will display messages the container has written to standard error or standard out.
Step 3 - Accessing Redis
$ docker run -d --name redisHostPort -p 6379:6379 redis:latest
29e98281a75cd2733edd7a5434d346627e7eae4fc1409a0f46118b97c0b190cf
Step 4 - Running A Container In The Foreground
The command docker run ubuntu pslaunches an Ubuntu container and executes the command ps to view all the processes running in a container.
Using docker run -it ubuntu bash allows Jane to get access to a bash shell inside of a container.
Step 1 - Create Dockerfile
Docker Images start from a base image. The base image should include the platform dependencies required by your application, for example, having the JVM or CLR installed.
This base image is defined as an instruction in the Dockerfile. Docker Images are built based on the contents of a Dockerfile. The Dockerfile is a list of instructions describing how to deploy your application.
In this example, our base image is the Alpine version of Nginx. This provides the configured web server on the Linux Alpine distribution.
Create your Dockerfile for building your image by copying the contents below into the editor.
Copy to EditorFROM nginx:alpineCOPY . /usr/share/nginx/htmlThe first line defines our base image. The second line copies the content of the current directory into a particular location inside the container.
Step 2 - Build Docker Image
Build our static HTML image using the build command below.
docker build -t webserver-image:v1 .You can view a list of all the images on the host using docker images.
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
webserver-image v1 ed7a9a1bfcbb 17 seconds ago 16.1MB
nginx alpine 0be75340bd9b 39 hours ago 16.1MB
redis latest 4760dc956b2d 13 months ago 107MB
ubuntu latest f975c5035748 13 months ago 112MB
alpine latest 3fd9065eaf02 15 months ago 4.14MB
$ curl docker
<h1>Hello World</h1>
The first line of the Dockerfile should be FROM nginx:1.11-alpine
FROM nginx:1.11-alpine
Task2 :
A new index.html file has been created for you which we want to serve from our container. On the next line after the FROM command, use the COPY command to copy index.html into a directory called /usr/share/nginx/html
Protip
If you're copying a file into a directory then you need to specify the filename as part of the destination.
COPY index.html /usr/share/nginx/html/index.html
Task3:
We want our web server to be accessible via port 80, add the relevant EXPOSE line to the Dockerfile.
EXPOSE 80
Task
The command to run NGINX is nginx -g daemon off;. Set this as the default command in the Dockerfile.
Protip
An alternative approach to CMD is ENTRYPOINT. While a CMD can be overridden when the container starts, a ENTRYPOINT defines a command which can have arguments passed to it when the container launches.
In this example, NGINX would be the entrypoint with -g daemon off; the default command.
CMD ["nginx", "-g", "daemon off;"]
Step 5 - Building Containers
Using the docker build command to build the image. You can give the image a friendly name by using the -t <name> option.
Protip
You can use docker images to see a list of the images on your local machine.
docker build -t my-nginx-image:latest . ( Instead of dot (.) you can specify the docker file.
Step 6 - Launching New Image
$ docker run -d -p 80:80 my-nginx-image:latest
9a89a8325d5fed557791322063ce922cda17b7de44959d8e5181572594ac5142
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
my-nginx-image latest b29d65df4ae0 4 minutes ago 54.3MB
redis latest 4760dc956b2d 13 months ago 107MB
ubuntu latest f975c5035748 13 months ago 112MB
alpine latest 3fd9065eaf02 15 months ago 4.14MB
nginx 1.11-alpine bedece1f06cc 2 years ago 54.3MB
sudo useradd Jenkins
sudo passwd Jenkins
sudo vi /etc/sudoers
usermod -aG docker jenkins
sudo usermod -aG docker Jenkins
sudo vi /etc/sudoers
sudo curl -L "https://github.com/docker/compose/releases/download/1.24.0/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
cd /usr/local/bin/
ls -ltr
sudo chmod +x /usr/local/bin/docker-compos
How to send commands to a docker client from docker engine.
docker exec -it jenkins cat /var/jenkins_home/secrets/initialAdminPassword
1 sudo apt-get update
2 sudo apt-get install apt-transport-https ca-certificates curl gnupg2 software-properties-common
3 curl -fsSL https://download.docker.com/linux/debian/gpg | sudo apt-key add -
4 sudo apt-key fingerprint 0EBFCD88
5 sudo apt-get install docker-ce
6 sudo apt-get install docker-ce docker-ce-cli containerd.io
7 sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/debian \
8 $(lsb_release -cs) \
9 stable"
10 sudo apt-get update
11 sudo apt-get install docker-ce docker-ce-cli containerd.io
12 docker ps
13 sudo docker ps
14 docker pull ubuntu
15 sudo docker pull ubuntu
16 docker image
17 docker images
18 sudo docker images
19 sudo docker exec -it d131e0fa2585 /bin/bash
20 sudo docker ps
21 sudo docker images
22 clear
23 sudo docker images
24 exit
25 sudo docker network inspect bridge
26 sudo docker network --help
27 sudo docker network create -d bridge mynw
28 docker network ls
29 sudo docker network ls
30 sudo docker ps
31 docker rmi ce048c7f00ae
32 sudo docker rmi ce048c7f00ae
33 docker images
34 sudo docker images
35 sudo docker rmi 7ad00eb59e26
36 sudo docker stop ce048c7f00ae
37 sudo docker rmi 7ad00eb59e26
38 sudo docker rmi -f 7ad00eb59e26
39 docker ps
40 sudo docker images
41 yum update -y
42 sudo su -
43 sudo docker ps
44 sudo docker images
45 sudo docker commit -tag git_maven:v.1 --name ubuntu_customized d131e0fa2585
46 sudo docker commit --tag git_maven:v.1 --name ubuntu_customized d131e0fa2585
47 sudo docker commit -t git_maven:v.1 --name ubuntu_customized d131e0fa2585
48 sudo docker commit tag d131e0fa2585 git_maven:v.1 --name ubuntu_customized
49 sudo docker commit tag d131e0fa2585 golden
50 sudo docker commit d131e0fa2585
51 docker ps
52 sudo docker ps
53 sudo docker commit a4c99b9f74ff
54 docker ps
55 sudo docker ps
56 sudo docker images
57 sudo docker commit --help
58 sudo docker tag --help
59 docker tag 7ad00eb59e26 cutomized:v.1
60 sudo docker tag 7ad00eb59e26 cutomized:v.1
61 sudo docker images
62 sudo docker push rkidambi/parasrepo:v2
63 sudo docker tag cutomized:v.1 rkidambi/parasrepo:v2
64 sudo docker push rkidambi/parasrepo:v2
65 sudo docker push rkidambi/parasrepo:cutomized
66 sudo docker tag cutomized:v.1 rkidambi/parasrepo:customized_os
67 sudo docker push rkidambi/parasrepo:cutomized_os
68 sudo docker push rkidambi/parasrepo:customized_os
69 sudo docker network inspect
70 sudo docker network inspect bridge
71 sudo docker network
72 sudo docker network ls
73 sudo inspect
74 sudo docker inspect
75 sudo docker inspect --help
76 sudo docker inspect ex
77 sudo docker ps
78 sudo docker inspect relaxed_turing
79 sudo docker network ls
80 docker ps
81 sudo dockerps
82 sudo docker ps
83 docker pull rkidambi/parasrepo:v1
84 sudo docker pull rkidambi/parasrepo:v1
85 sudo docker pull rkidambi/parasrepo:v2
86 docker ps
87 sudo docker images
88 docker ps
89 sudo docker ps
90 sudo docker exec -itd 7ad00eb59e26 /bin/bash
91 sudo docker run -itd 7ad00eb59e26
92 sudo docker ps
93 sudo docker run -itd 7ad00eb59e26
94 sudo docker ps
95 sudo docker network disconnect bridge 2cb3d3fc0fb4
96 docker ps
97 sudo docker ps
98 sudo docker network inspect bridge
99 sudo docker network connect bridge mynw objective_feistel
100 docker network connect mynw objective_feistel
101 sudo docker network inspect mynw
102 sudo docker network connect mynw objective_feistel
103 sudo docker network inspect mynw
104 sudo docker ps
105 docker images
106 sudo docker images
107 sudo docker run -itd cutomized /bin/bash
108 sudo docker run -itd cutomized:v.1 /bin/bash
109 docker ps
110 sudo docker ps
111 docker login
112 sudo docker login
113 sudo docker tag cutomized:v.1 rkidambi/ubuntu:v1
114 docker images
115 sudo docker images
116 docker push rkidambi/ubuntu
117 sudo docker push rkidambi/ubuntu
118 sudo docker ps
119 sudo docker images
120 sudo docker run -itd ubuntu
121 docker ps
122 sudo docker ps
123 sudo docker exec -it a4c99b9f74ff /bin/bash
124 df -h
125 sudo docker exec -it a4c99b9f74ff /bin/bash
In 1.12, Docker introduced Swarm Mode. Swarm Mode enables the ability to deploy containers across multiple Docker hosts, using overlay networks for service discovery with a built-in load balancer for scaling the services.
Swarm Mode is managed as part of the Docker CLI, making it a seamless experience to the Docker ecosystem.
Docker Swarm Mode introduces three new concepts which we'll explore in this scenario.
This scenario will help you learn how to deploy these new concepts.
Step 1 - Initialise Swarm Mode
Turn single host Docker host into a Multi-host Docker Swarm Mode. Becomes Manager By default, Docker works as an isolated single-node. All containers are only deployed onto the engine. Swarm Mode turns it into a multi-host cluster-aware engine.
The first node to initialise the Swarm Mode becomes the manager. As new nodes join the cluster, they can adjust their roles between managers or workers. You should run 3-5 managers in a production environment to ensure high availability.
Swarm Mode is built into the Docker CLI. You can find an overview the possibility commands via docker swarm --help
The most important one is how to initialise Swarm Mode. Initialisation is done via init.
docker swarm initAfter running the command, the Docker Engine knows how to work with a cluster and becomes the manager. The results of an initialisation is a token used to add additional nodes in a secure fashion. Keep this token safe and secure for future use when scaling your cluster.
In the next step, we will add more nodes and deploy containers across these hosts.
Step 2 - Join Cluster
With Swarm Mode enabled, it is possible to add additional nodes and issues commands across all of them. If nodes happen to disappear, for example, because of a crash, the containers which were running on those hosts will be automatically rescheduled onto other available nodes. The rescheduling ensures you do not lose capacity and provides high-availability.
On each additional node, you wish to add to the cluster, use the Docker CLI to join the existing group. Joining is done by pointing the other host to a current manager of the cluster. In this case, the first host.
Docker now uses an additional port, 2377, for managing the Swarm. The port should be blocked from public access and only accessed by trusted users and nodes. We recommend using VPNs or private networks to secure access.
The first task is to obtain the token required to add a worker to the cluster. For demonstration purposes, we'll ask the manager what the token is via swarm join-token. In production, this token should be stored securely and only accessible by trusted individuals.
token=$(docker -H 172.17.0.4:2345 swarm join-token -q worker) && echo $tokenOn the second host, join the cluster by requesting access via the manager. The token is provided as an additional parameter.
docker swarm join 172.17.0.4:2377 --token $tokenBy default, the manager will automatically accept new nodes being added to the cluster. You can view all nodes in the cluster using docker node ls
Step 3 - Create Overlay Network
Swarm Mode also introduces an improved networking model. In previous versions, Docker required the use of an external key-value store, such as Consul, to ensure consistency across the network. The need for consensus and KV has now been incorporated internally into Docker and no longer depends on external services.
The improved networking approach follows the same syntax as previously. The overlay network is used to enable containers on different hosts to communicate. Under the covers, this is a Virtual Extensible LAN (VXLAN), designed for large scale cloud based deployments.
The following command will create a new overlay network called skynet. All containers registered to this network can communicate with each other, regardless of which node they are deployed onto.
docker network create -d overlay skynet