Docker learning Phase-I


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# 1  
Docker learning Phase-I

Hello All,

I had recently learnt a bit of Docker(which provides containerization process).
Here are some of my learning points from it.

Let us start first with very basic question:

What is Docker:
Docker is a platform for sysadmins and developers to DEPLOY, DEVELOP and RUN applications with containers.

The use of Linux containers to deploy applications is called containerization.

Flexible: Even the most complex applications can be containerized.
Lightweight: Containers leverage and share the host kernel.
Interchangeable: You can deploy updates and upgrades on-the-fly.
Portable: You can build locally, deploy to the cloud, and run anywhere.
Scalable: You can increase and automatically distribute container replicas.
Stackable: You can stack services vertically and on-the-fly.


What is an Image: We could say Image as an executable which has all things needed to run an application EG--> code, libraries, environment variables, config files.

What is Container: Whenever we run an image then its executable form is called Container.

Prerequisites: Ubuntu/Linux server then in case you need to publish your images to Docker repository an account on Docker HUB.

Steps for installing Docker:

1st Step: Use curl command to install its binaries along with apt-key to make sure downloads are valid.

Code:
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

2nd Step: Add Docker repository to APT resources:
Code:
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"

3rd Step: Update apt-get for Ubuntu server(where we are going to learn Docker)
Code:
sudo apt-get update

4th Step: To make sure we are going to install Docker from Docker's repo rather than default Ubuntu 16.04 repo run following.
Code:
apt-cache policy docker-ce

5th Step: Finally Install Docker now.
Code:
sudo apt-get install -y docker-ce

6th Step: Run systemctl to make sure that this service is added in rc boot of server and should come up after reboot of server.
Code:
sudo systemctl status docker

● docker.service - Docker Application Container Engine
   Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
   Active: active (running) since Thu 2018-10-18 20:28:23 UTC; 35s ago
     Docs: https://docs.docker.com
 Main PID: 13412 (dockerd)
   CGroup: /system.slice/docker.service
           ├─13412 /usr/bin/dockerd -H fd://
           └─13421 docker-containerd --config /var/run/docker/containerd/containerd.toml

7th Step: Now lets run only docker command and see what output is coming.
Code:
  attach      Attach local standard input, output, and error streams to a running container
  build       Build an image from a Dockerfile
  commit      Create a new image from a container's changes
  cp          Copy files/folders between a container and the local filesystem
  create      Create a new container
  diff        Inspect changes to files or directories on a container's filesystem
  events      Get real time events from the server
  exec        Run a command in a running container
  export      Export a container's filesystem as a tar archive
  history     Show the history of an image
  images      List images
  import      Import the contents from a tarball to create a filesystem image
  info        Display system-wide information
  inspect     Return low-level information on Docker objects
  kill        Kill one or more running containers
  load        Load an image from a tar archive or STDIN
  login       Log in to a Docker registry
  logout      Log out from a Docker registry
  logs        Fetch the logs of a container
  pause       Pause all processes within one or more containers
  port        List port mappings or a specific mapping for the container
  ps          List containers
  pull        Pull an image or a repository from a registry
  push        Push an image or a repository to a registry
  rename      Rename a container
  restart     Restart one or more containers
  rm          Remove one or more containers
  rmi         Remove one or more images
  run         Run a command in a new container
  save        Save one or more images to a tar archive (streamed to STDOUT by default)
  search      Search the Docker Hub for images
  start       Start one or more stopped containers
  stats       Display a live stream of container(s) resource usage statistics
  stop        Stop one or more running containers
  tag         Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
  top         Display the running processes of a container
  unpause     Unpause all processes within one or more containers
  update      Update configuration of one or more containers
  version     Show the Docker version information
  wait        Block until one or more containers stop, then print their exit codes

8th Step: Check for docker version by running as follows.
Code:
docker --version
Docker version 18.09.0, build 4d60db4

9th Step: Pull first image from Docker's repository as follows.
Code:
docker run hello-world

Output approximate will be as follows.
Code:
...
Hello from Docker!
This message shows that your installation appears to be working correctly.
...

Will post further details on how to call a basic Python program through Docker image and show how it will NOT require packages(needed by that program) for your Ubuntu server(they will be their in containers to support programs not in local server).

One could refer Docker site's documentation in link Docker Documentation | Docker Documentation too.

Stay tuned with this thread. Your edits/views/comments/feed back are Welcome Smilie


Hello Neo,

Would like to request you if we can create a new forum for Docker, so users could post threads there.
Kindly do let me know your views on same.


Thanks,
R. Singh

Last edited by RavinderSingh13; 01-06-2019 at 08:56 AM..
These 2 Users Gave Thanks to RavinderSingh13 For This Post:
# 2  
The installation process only takes Debian-based distributions into account. It can be installed on RedHat-derived distributions using rpm (CentOS, Fedora, RedHat, RHEL, SuSE) using this procedure if you have yum or this procedure using zypper.

Also notice that for RHEL (the enterprise version of RedHat) and SLES (the enterprise version of SuSE) only Docker EE (Enterprise Edition) is supported. It is entirely possible to install the CE versions (i.e. for test purposes) but of course this voids all support from RedHat, SuSE, etc..

bakunin

Last edited by bakunin; 01-06-2019 at 09:13 AM.. Reason: corrected link
These 2 Users Gave Thanks to bakunin For This Post:
# 3  
Quote:
Originally Posted by RavinderSingh13
Hello Neo,

Would like to request you if we can create a new forum for Docker, so users could post threads there.
Kindly do let me know your views on same.


Thanks,
R. Singh
Done.

https://www.unix.com/docker/
This User Gave Thanks to Neo For This Post:
# 4  
Wouldn't it be more wider to not limit to 'Docker' but a more general 'Containers' ?
This would, in theory, cover all possible container variations, starting from zones, jails to any kubernets implementation (docker, c-rio etc.)

The 'containers' would be a focal point to seek advice about all single kernel virtualization techs and their implementations such as docker swarm, openshift, zoneclusters etc.
It's a very big topic regarding security, implementation, network layer (vxlans), various APIs and build/versioning tools.

Regards
Peasant.
These 3 Users Gave Thanks to Peasant For This Post:
# 5  
Yes I scond "Containers". Docker and others to be mentioned in the short description.
Some years ago there was a discussion "Nagios" versus "Infrastructure Monitoring"...
# 6  
Peasant is right. An now, that MadeInGermany mentioned it, my failing memory disinterred this discussion too.

bakunin
# 7  
I think, for now, I leave it as "Docker" because I seriously doubt we will see a lot of "container" posts; and Ravinder's goal is to focus on Docker and attract Docker users.

If anyone wants to post a lot of "Container" discussions, then we will consider making a "Container" forum. Having a specific forum is not going to cause people to post; and in the past, specific names to forums that were requested also did not result in people flocking to post because a forum had a specific name.

So in my view, we don't need to think about "forums" too much, just tag "containers" and behold, we have full access to all container discussions.

Ravinder wanted a Docker forum, so he has one because he plans to post a lot here. If he does not follow though, I will eventually move all the discussions in the "Docker" forum elsewhere.
This User Gave Thanks to Neo For This Post:
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