lab/DockerSwarm/Intro-Cloud.adoc

= Εισαγωγή στο Cloud !
Apostolos rootApostolos@swarmlab.io
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== Cloud - Intro

Cloud computing is the **on-demand availability of computer system resources**, especially data storage and computing power, without direct active management by the user. The term is generally used to describe data centers available to many users over the Internet. 

Large clouds, predominant today, often have functions distributed over multiple locations from central servers. If the connection to the user is relatively close, it may be designated an edge server.

Clouds may be limited to a single organization (enterprise clouds), or be available to many organizations (public cloud).

Cloud computing relies on sharing of resources to achieve coherence and economies of scale. 

image:./Cloud_computing.svg.png[alt="Cloud_computing"] +
From Wikipedia, the free encyclopedia +
https://en.wikipedia.org/wiki/Cloud_computing[^]




=== Cloud Computing Tutorial for Beginners

* Cloud Computing Tutorial for Beginners
+
video::RWgW-CgdIk0[youtube]


== Cloud computing architecture

Cloud computing architecture refers to the components and subcomponents required for cloud computing. These components typically consist of a front end platform (fat client, thin client, mobile device), back end platforms (servers, storage), a cloud based delivery, and a network (Internet, Intranet, Intercloud). Combined, these components make up cloud computing architecture. 

=== Virtualization

In computing, virtualization refers to the act of creating a virtual (rather than actual) version of something, including virtual computer hardware platforms, storage devices, and computer network resources. 

=== Containerization

Containerization has become a major trend in software development as an alternative or companion to virtualization. It involves encapsulating or packaging up software code and all its dependencies so that it can run uniformly and consistently on any infrastructure. The technology is quickly maturing, resulting in measurable benefits for developers and operations teams as well as overall software infrastructure.

=== Virtual Machines vs Docker Containers

- A container image is a lightweight, stand-alone, executable package of a piece of software that includes everything needed to run it.

Docker is the service to run multiple containers on a machine (node) which can be on a vitual machine or on a physical machine.

- A virtual machine is an entire operating system (which normally is not lightweight).


* Virtual Machines vs Docker Containers
+
video::TvnZTi_gaNc[youtube]

==== Docker Containers

image:./container-what-is-container.png[alt="Container",align="center",width=550,height=550] 


==== Virtual Machines 

image:./container-vm-whatcontainer_2.png[alt="VirtualMachine",align="center",width=550,height=550] 

==  Orchestration

Container orchestration automates the deployment, management, scaling, and networking of containers. Enterprises that need to deploy and manage hundreds or thousands of Linux® containers and hosts can benefit from container orchestration. 
Container orchestration can be used in any environment where you use containers. It can help you to deploy the same application across different environments without needing to redesign it. And microservices in containers make it easier to orchestrate services, including storage, networking, and security. 

Containers give your microservice-based apps an ideal application deployment unit and self-contained execution environment. They make it possible to run multiple parts of an app independently in microservices, on the same hardware, with much greater control over individual pieces and life cycles.

Managing the lifecycle of containers with orchestration also supports DevOps teams who integrate it into CI/CD workflows. Along with application programming interfaces (APIs) and DevOps teams, containerized microservices are the foundation for cloud-native applications.


Container orchestration used for:

-    Provisioning and deployment
-    Configuration and scheduling 
-    Resource allocation
-    Container availability 
-    Scaling or removing containers based on balancing workloads across your infrastructure
-    Load balancing and traffic routing 
-    Monitoring container health
-    Configuring applications based on the container in which they will run
-    Keeping interactions between containers secure

===  Kubernetes vs Docker Swarm

* Kubernetes vs Docker Swarm
+
video::FmrAGliHvzQ[youtube]

=== Technical Comparisons

image:./1-2-683x1024.png[alt="dockerSwarmVsKubernetes"] +
image:./2-1-683x1024.png[alt="dockerSwarmVsKubernetes"] +



=== Conclusion

When comparing Docker Swarm vs Kubernetes, it becomes apparent that the origins of both platforms have played key roles in shaping their features and communities today.

Docker, realizing the strength of its container technology, decided to build a platform that made it simple for Docker users to begin orchestrating their container workloads across multiple nodes. However, their desire to preserve this tight coupling can be said to have limited the extensibility of the platform.

Kubernetes, on the other hand, took key concepts taken from Google Borg, and, from a high level perspective, decided to make containerization fit into the former platform’s existing workload orchestration model. This resulted in Kubernetes emphasis on reliability, sometimes at the cost of simplicity and performance.


=== Popularity of searches for each platform

image:./Screen-Shot-2018-01-09-at-5.59.05-PM-700x410.png[alt="dockerSwarmVsKubernetes"] +

Origin: 
https://www.nirmata.com/2018/01/15/orchestration-platforms-in-the-ring-kubernetes-vs-docker-swarm



== Docker


=== Images

In Docker, everything is based on Images. An image is a combination of a file system and parameters.

==== Dockerfile

A Dockerfile is a simple text file that contains a list of commands that the Docker client calls while creating an image. It's a simple way to automate the image creation process. The best part is that the commands you write in a Dockerfile are almost identical to their equivalent Linux commands. This means you don't really have to learn new syntax to create your own dockerfiles.

.Dockerfile
[source,sh]
----
FROM ubuntu:16.04
ENV DEBIAN_FRONTEND noninteractive
RUN apt-get update -y && \
    apt-get -y install gcc && \
    rm -rf /var/lib/apt/lists/*
----

==== docker build

.docker build
[source,sh]
----
docker build  -t ImageName:TagName dir

Options

    -t − is to mention a tag to the image

    ImageName − This is the name you want to give to your image.

    TagName − This is the tag you want to give to your image.

    Dir − The directory where the Docker File is present.
----

.docker build example
[source,sh]
----
docker build –t myimage:0.1 .
----


==== Displaying Docker Images

To see the list of Docker images on the system, you can issue the following command.

.docker images
[source,sh]
----
docker images
----

This command is used to display all the images currently installed on the system.


**Output:**

-    TAG − This is used to logically tag images.
-    Image ID − This is used to uniquely identify the image.
-    Created − The number of days since the image was created.
-    Virtual Size − The size of the image.


=== Containers

Containers are instances of Docker images that can be run using the Docker run command. The basic purpose of Docker is to run containers. 


==== Running a Container

Running of containers is managed with the Docker run command. To run a container in an interactive mode, first launch the Docker container.

.run docker image
[source,sh]
----
docker run –it myimage /bin/bash 
----


==== Listing of Containers

One can list all of the containers on the machine via the docker ps command. This command is used to return the currently running containers.

.run docker image
[source,sh]
----
docker ps
----

==== Display the running processes of a container


With this command, you can see the top processes within a container.
Syntax

.docker top
[source,sh]
----
docker top ContainerID 

Options

    ContainerID − This is the Container ID for which you want to see the top processes.
----

==== Stop a running container

This command is used to stop a running container.

.docker stop
[source,sh]
----
docker stop ContainerID 

Options

    ContainerID − This is the Container ID which needs to be stopped.
----

==== Attach a running container


This command is used to attach to a running container.

.docker 
[source,sh]
----
docker attach ContainerID 

Options

    ContainerID − This is the Container ID to which you need to attach.
----


==== Delete container

This command is used to delete a container.

.docker rm
[source,sh]
----
docker rm ContainerID 

Options

    ContainerID − This is the Container ID which needs to be removed.
----









:hardbreaks:

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'''

.Reminder
[NOTE]
====
:hardbreaks:
Caminante, no hay camino, 
se hace camino al andar.

Wanderer, there is no path, 
the path is made by walking.

*Antonio Machado* Campos de Castilla
====