docker base image

1. What is a docker base image?
2. What is the default Docker image?
3. What is Docker image layer?
4. Where do I find Docker images?
5. Can a docker image run on any OS?
6. Can I run a different OS in Docker?
7. How do I run an image in Docker?
8. How do I start Docker?
9. How Docker image is created?
10. What is the difference between Docker image and layer?
11. What are the layers in Docker?
12. What are image layers?

What is a docker base image?

A base image is the image that is used to create all of your container images. Your base image can be an official Docker image, such as Centos, or you can modify an official Docker image to suit your needs, or you can create your own base image from scratch.

What is the default Docker image?

The default docker images will show all top level images, their repository and tags, and their size. Docker images have intermediate layers that increase reusability, decrease disk usage, and speed up docker build by allowing each step to be cached. These intermediate layers are not shown by default.

What is Docker image layer?

Basically, a layer, or image layer is a change on an image, or an intermediate image. Every command you specify ( FROM , RUN , COPY , etc.) in your Dockerfile causes the previous image to change, thus creating a new layer.

Where do I find Docker images?

The heaviest contents are usually images. If you use the default storage driver overlay2, then your Docker images are stored in /var/lib/docker/overlay2 . There, you can find different files that represent read-only layers of a Docker image and a layer on top of it that contains your changes.

Can a docker image run on any OS?

No, Docker containers can't run on all operating systems directly, and there are reasons behind that. Let me explain in detail why Docker containers won't run on all operating systems. Docker container engine was powered by the core Linux container library (LXC) during the initial releases.

Can I run a different OS in Docker?

No, it does not. Docker uses containerisation as a core technology, which relies on the concept of sharing a kernel between containers. If one Docker image relies on a Windows kernel and another relies on a Linux kernel, you cannot run those two images on the same OS.

How do I run an image in Docker?

To run an image inside of a container, we use the docker run command. The docker run command requires one parameter and that is the image name. Let's start our image and make sure it is running correctly. Execute the following command in your terminal.

How do I start Docker?

Get started with Docker Compose

1. Step 1: Setup. ...
2. Step 2: Create a Dockerfile. ...
3. Step 3: Define services in a Compose file. ...
4. Step 4: Build and run your app with Compose. ...
5. Step 5: Edit the Compose file to add a bind mount. ...
6. Step 6: Re-build and run the app with Compose. ...
7. Step 7: Update the application. ...
8. Step 8: Experiment with some other commands.

How Docker image is created?

Create a Docker image from an existing container: In this case, you start with an existing image, customize it with the changes you want, then build a new image from it. Use a Dockerfile: In this case, you use a file of instructions — the Dockerfile — to specify the base image and the changes you want to make to it.

What is the difference between Docker image and layer?

When you pull an image from Docker hub, "layers" have "" Image IDs. When you commit changes to locally built images, these layers will have Images IDs. ... A Docker image is a read-only template. For example, an image could contain an Ubuntu operating system with Apache and your web application installed.

What are the layers in Docker?

A Docker image consists of several layers. Each layer corresponds to certain instructions in your Dockerfile . The following instructions create a layer: RUN , COPY , ADD . The other instructions will create intermediate layers and do not influence the size of your image.

What are image layers?

Layers are used in digital image editing to separate different elements of an image. A layer can be compared to a transparency on which imaging effects or images are applied and placed over or under an image.