This document provides an introduction to Docker presented by Adrian Otto. It defines Docker components like the Docker Engine (CLI and daemon), images, containers and registries. It explains how containers combine cgroups, namespaces and images. It demonstrates building images with Dockerfiles, committing container changes to new images, and the full container lifecycle. Finally, it lists Docker CLI commands and promises a demo of building/running containers.

1. Docker 101
Intro to Docker
Presented by: Adrian Otto
Prepared for: Austin Tech Talk
Date: May 28, 2015

2. Adrian Otto
• Principal Architect, Rackspace
• OpenStack Magnum PTL
• Solum PTL
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4. What is it?
• Docker Engine
– CLI
– Docker Daemon
– Docker Registry
• Docker Hub
– Cloud service
•Share Applications
•Automate workflows
•Assemble apps from components
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6. Container
• Combines several things
– Linux Cgroups
– Kernel Namespaces
– Docker Image
– Has a lifecycle
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7. Linux Cgroups
• Kernel Feature
• Groups of processes
• Control resource allocations
– CPU
– Memory
– Disk
– I/O
• May be nested
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8. Linux Kernel Namespaces
• Kernel Feature
• Restrict your view of the system
– Mounts (CLONE_NEWNS)
– UTS (CLONE_NEWUTS)
• uname() output
– IPC (CLONE_NEWIPC)
– PID (CLONE_NEWPID)
– Networks (CLONE_NEWNET)
– User (CLONE_NEWUSER)
•Not supported in Docker yet
•Has privileged/unprivileged modes today
• May be nested
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9. Docker Image
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• NOT A FILESYSTEM
• NOT A VHD
• Basically a tar file
• Has a hierarchy
• Arbitrary depth
• Fits into the Docker Registry

10. Docker Registry
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• Git Repo Semantics
• Pull
• Push
• Commit
• Hierarchy

11. Container
• Combines several things
– Linux Cgroups
– Kernel Namespaces
– Docker Image
– Has a lifecycle
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12. Dockerfile
• Like a Makefile (shell script with keywords)
• Extends from a Base Image
• Results in a new Docker Image
• Imperative, not Declarative
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13. Dockerfile Example
FROM centos
MAINTAINER aotto@aotto.com
RUN yum -y install openssh-server
EXPOSE 22
ADD start.sh /start.sh
CMD /start.sh
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14. Dockerfile Example
FROM adrian_server_with_ssh
MAINTAINER aotto@aotto.com
RUN yum -y install httpd
EXPOSE 22 80
ADD start.sh /start.sh
CMD /start.sh
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15. • The Life of a Container
– Conception
•BUILD an Image from a Dockerfile
– Birth
•RUN (create+start) a container
– Reproduction
•COMMIT (persist) a container to a new image
•RUN a new container from an image
– Sleep
•KILL a running container
– Wake
•START a stopped container
– Death
•RM (delete) a stopped container
• Extinction
– RMI a container image (delete image)
Docker Container Lifecycle
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16. Docker CLI Commands (v1.1.2)
attach Attach to a running container
build Build an image from a Dockerfile
commit Create new image from container's
changes
cp Copy files from containers fs to host
diff Inspect changes on a container's fs
events Get real time events from the server
export Stream contents of container as tar
history Show the history of an image
images List images
import Create new fs image from a tarball
info Display system-wide information
inspect Return low-level info on a container
kill Kill a running container
load Load an image from a tar archive
login Login to the docker registry server
logs Fetch the logs of a container
port Lookup public-facing port
pause Pause all processes within a container
ps List containers
pull Pull image or repo from docker registry
push Push image or repo to docker registry
restart Restart a running container
rm Remove one or more containers
rmi Remove one or more images
run Run a command in a new container
save Save an image to a tar archive
search Search for an image in the docker index
start Start a stopped container
stop Stop a running container
tag Tag an image into a repository
top Lookup running processes of a container
unpause Unpause a paused container
version Show the docker version information
wait Block and print exit code upon cont
exit
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Questions Before Demo?

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Demo

19. Demo
• Build an Image from a Dockerfile
• Manually tweak an image, commit, and start a new container
• Install patches in a container, and tag it as :latest
• Show different distros running on the same kernel
• Run a container using a different CMD than the built-in one
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