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We are done with both Dockerfile and Docker Images.

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So now, it is time to pay our much needed

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attention to the center point of this course, containers.

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[No Audio]

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We have already seen the formal definition of

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containers. But if we consider our updated

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knowledge, the simplest way to describe a

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container would be a running instance of a Docker Image.

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You can compare it to the analogy of process and

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program in Linux. Just like a process is a running

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instance of a program, a container is a running instance of an image.

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With help of namespaces on the Linux host,

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containers provide similar isolations like VM.

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Each container has its own file system, network

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driver, storage driver, and administrative

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privileges as well. Despite of all of this, any

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container would be at least 100 times lighter than

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the VMs hosting the same set of softwares.

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[No Audio]

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We have seen previously that Docker Images are

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made of read only layers, and the top most layer is writable.

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Well, this top layer is provided to it

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while creating a container out of the image.

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With correct network configurations, containers

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can also talk to each other via IP or DNS.

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It also follows Copy-on-Write policy to maintain

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the integrity of the Docker image, which we will explore soon.

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[No Audio]

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You may wonder what exactly do we mean by running

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the image? Well, much less to the surprise.

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Run can be defined pretty simply in our context.

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It means providing resources like compute, memory and storage.