Names

Names

The Good

Docker is a company

docker is a container management tool

The Bad

Containerize not dockerize

The Ugly

I have an application in a docker

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What is so spacial about Docker

In the beginning there were logical partitions (LPARs)

Made by our parents

Then came Linux Containers (LXC)

Made by our brothers and sisters

Interface to cgroups and namespaces in the kernel

The rise of Docker

Founded 2013 by Solomon Hykes

He revolutionized container management

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Concepts

Process Isolation

Processes cannot see the host OS

Processes cannot see into other containers

Kernel is responsible

Isolation

Resource management

Containers are immutable

Configuration changes only when created

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Containers vs. VMs

Different levels of virtualization

Hardware virtualization isolated operating systems

Containers isolate processes

XXX illustration

Containers are just another option!

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Advantages

Development

Reproducible environment

Packaged runtime environment

Deployable for testing

Operations

Lightweight virtualization

Density

Dependency management

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Nomenclature

Container

Isolated process

Runtime environment

Image

Base image to create identical containers from

Immutable

Registry

Plce to store images

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Container

Isolated processes

Shared, read-only image

Dedicated, writable volume

Network

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Why Containers

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Internals

Namespaces

• Used for resource isolation
• Isolation of resource usage to limit visibility
• Types are PID, network, mount

c(ontrol)groups

• Used to limit resource usage for proceses
• Limits and measures access to…
• …CPU, memory, network, IO

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Docker

Packaged

• Includes dependencies
• Distributable

Immutable

• Incremental changes not supported
• Changes require rollout

Automated

• Image builds
• Deployments

Stateless

• By default, no persistence

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Relevance of Docker

With regard to…

Orchestration

• No, Kubernetes has won

Container runtime

• Often, but containerd is growing quickly

Image build

• Yes
• Other image builders are still niche players
• Examples: buildah, img, kaniko (list not exhaustive)

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Containers

Process Isolation

Dedicated resources

Resource reservation / limitation

But… it’s just a process