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Docker packages apps into a single unit, called an image. When these images are run via Docker, they're called containers, where a single container is an instance of an image. It's possible to run many containers based on a single image.
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Docker packages apps into a single unit called an image.
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When these images are run via Docker they're called containers.
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Where a single container is an instance of an image,
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it's possible to run many containers based on a single image.
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You can think of a container as a shipping container, just like you'd see on ships.
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Within each shipping container could be many different kinds of contents.
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But because they're all uniform in shape,
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they can all be handled the same way even though their content is different.
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Usually the contents of a container are related in some way and
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will be delivered to the same location.
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In Docker, the contents of a container come together to form a singular unit
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that represents an app, service, website or any single piece of software.
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Docker packages the programs, services, and libraries your app depends on in to
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an image along with your instructions on how to run it.
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And the environment it should run in.
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This all gets taken by docker and run on the host machine as a container.
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An image is a mutable file that essentially a snapshot of a container.
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They're created with the build command.
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And they produce a container when started with the run command.
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Images can be stored in the Docker registry, which is like a GitHub for
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Docker images.
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Then they could be retrieved later on the system where you wanna deploy them.
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Because images can become pretty large,
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they're designed to be composed of layers of other images.
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That means, we only have to send small amounts of data over the network
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when transferring images.
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To make all this magic happen, Docker uses three major components.
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The Docker daemon, which is a process running on your host OS.
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Docker registries,
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which are servers daemons connect to in order to retrieve images they need.
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And the Docker client, which issues commands to the Docker daemon.
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The Docker daemon coordinates running containers, packaging images and
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transferring images to and from registries.
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The Docker command line interface or client is what you see.
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The client is where you run commands on the host machine.
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To spin up new Docker containers, build Docker files into images,
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monitor running containers and many other tasks.
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Docker registries store Docker images.
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We talked about Docker hub earlier which is the public registry anyone can use.
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The Docker tools are configured to talk to Docker hub by default.
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But that's just one of the available registries.
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Docker cloud is another one.
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And you can run a private registry on your company's own servers if you want.
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If you run a Docker pull command using the Docker client,
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the Docker daemon will connect to a Docker registry, retrieve an image, and
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store it on the Docker host machine.
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When you use the Docker run command,
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the Docker daemon launches a copy of a locally stored image as a new container.
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You can even run your own private registry within your organization.
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Which allows you to manage your company's images without pushing them to the public
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Docker registry.
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