Rusty  Shanahan

Rusty Shanahan

1593351300

Docker under the Hood — 2. Container from Scratch, and Image Storage

In the previous article of this series, we discussed about the contents of a docker iamge — the root filesystem, and the configuration. We also tried to download the mini root filesystem of an alpine linux, and we inspected some of the configurations of a docker image (if you haven’t done so, please read the previous article first).

#containers #cloud-computing #software-development #devops #docker

What is GEEK

Buddha Community

Docker under the Hood — 2. Container from Scratch, and Image Storage
Mikel  Okuneva

Mikel Okuneva

1602317778

Ever Wondered Why We Use Containers In DevOps?

At some point we’ve all said the words, “But it works on my machine.” It usually happens during testing or when you’re trying to get a new project set up. Sometimes it happens when you pull down changes from an updated branch.

Every machine has different underlying states depending on the operating system, other installed programs, and permissions. Getting a project to run locally could take hours or even days because of weird system issues.

The worst part is that this can also happen in production. If the server is configured differently than what you’re running locally, your changes might not work as you expect and cause problems for users. There’s a way around all of these common issues using containers.

What is a container

A container is a piece of software that packages code and its dependencies so that the application can run in any computing environment. They basically create a little unit that you can put on any operating system and reliably and consistently run the application. You don’t have to worry about any of those underlying system issues creeping in later.

Although containers were already used in Linux for years, they became more popular in recent years. Most of the time when people are talking about containers, they’re referring to Docker containers. These containers are built from images that include all of the dependencies needed to run an application.

When you think of containers, virtual machines might also come to mind. They are very similar, but the big difference is that containers virtualize the operating system instead of the hardware. That’s what makes them so easy to run on all of the operating systems consistently.

What containers have to do with DevOps

Since we know how odd happenings occur when you move code from one computing environment to another, this is also a common issue with moving code to the different environments in our DevOps process. You don’t want to have to deal with system differences between staging and production. That would require more work than it should.

Once you have an artifact built, you should be able to use it in any environment from local to production. That’s the reason we use containers in DevOps. It’s also invaluable when you’re working with microservices. Docker containers used with something like Kubernetes will make it easier for you to handle larger systems with more moving pieces.

#devops #containers #containers-devops #devops-containers #devops-tools #devops-docker #docker #docker-image

Rusty  Shanahan

Rusty Shanahan

1593351300

Docker under the Hood — 2. Container from Scratch, and Image Storage

In the previous article of this series, we discussed about the contents of a docker iamge — the root filesystem, and the configuration. We also tried to download the mini root filesystem of an alpine linux, and we inspected some of the configurations of a docker image (if you haven’t done so, please read the previous article first).

#containers #cloud-computing #software-development #devops #docker

August  Murray

August Murray

1615008840

Top 24 Docker Commands Explained with Examples

In my previous blog post, I have explained in detail how you can Install Docker and Docker-compose on Ubuntu

In this guide, I have explained the Top 24 Docker Commands with examples.

Make sure you have sudo or root privileges to the system.

Docker Commands

  1. The command to check the version of Docker installed.
  2. To look/search for available docker images from the Docker registry.
  3. To pull docker images from the Docker registry.
  4. Listing all the docker images
  5. Creating / Running docker container from Docker image.
  6. To list the actively running docker containers.
  7. To list all the docker containers
  8. To stop a Container
  9. To start a Container
  10. To restart a Docker container
  11. To login to running Docker container
  12. To delete the stopped Docker containers
  13. To delete Docker images from the Local system
  14. To check logs of a running Docker container
  15. Killing docker containers
  16. Log in to Docker Hub registry (hub.docker.com)
  17. Removing docker hub registry login from the system.
  18. Check active resource usage by each containers
  19. Rename a Docker container
  20. To display system wide information of Docker
  21. Inspecting a Docker container
  22. Building docker images from Docker file
  23. Creating new docker images from a Container
  24. Pushing Docker images from Local to Docker registry.

#docker #docker-command #containers #docker-compose #docker-image

Elton  Bogan

Elton Bogan

1596661320

Docker Image and Container

Docker_ enables developers to easily pack, ship, and run any application as a lightweight, portable, self-sufficient container, which can run virtually anywhere. … Containers do this by enabling developers to isolate code into a single container. This makes it easier to modify and update the program_

Image for post

Lets start by defining a docker file. It is a simple file which includes details about base image, dependencies and command line argument (if needed).The below docker file is to create simple python based docker image.

Image for post

The first line denoted the base image I am using to create docker. And then I am copying all the files and folder from my current directory to docker pod.Just to be clear, the folder structure is as shown below.

Image for post

Image for post

cmd.py

cmd.py is a simple python script to print “Hello World” with a help of flask framework. The text file requirement.txt includes all the necessary libraries I need to run the script. From the .py file it is very evident that I need only “flask”, hence I can replace the fourth line of dockerfile with “RUN pip install flask”. 🙏

Now lets launch Docker to create an image!

Once we are in the folder location, we need to run a very simple command

#dockerfiles #docker #docker-image #containers #python

Docker manifest - A peek into image's manifest.json files

docker manifest – An experimental feature !

The image manifest provides a configuration and a set of layers for a container image.

This is an experimental feature. To enable this feature in the Docker CLI, one can edit the config.json file found in ~/.docker/config.json like :

{
        "auths": {
                "https://index.docker.io/v1/": {
                        "auth": "XXXXXXX"
                }
        },
        "HttpHeaders": {
                "User-Agent": "Docker-Client/19.03.8 (linux)"
        },
        "experimental": "enabled",
        "debug": true
}

What is ‘docker manifest’ ?

The docker manifest command does not work independently to perform any action. In order to work with the docker manifest or manifest list, we use sub-commands along with it. This manifest sub-command can enable us to interact with the image manifests. Furthermore, it also gives information about the OS and the architecture, that a particular image was built for.

A single manifest comprises of information about an image, it’s size, the layers and digest.

A manifest list is a list of image layers (manifests) that are, created by specifying one or more image names. It can then be used in the same way as an image name in docker pull and docker run commands.

Commands to get started with :

After enabling this feature, one would be able to access the following command :

docker-manifest-enter image description here

These commands are easy to use. It basically avoids the need for pulling and running and then testing the images locally, from a docker registry.

Next, to inspect an image manifest, follow this syntax,

 docker manifest inspect image-name

enter image description here

.

#devops #docker #devops #docker #docker learning #docker-image