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Luciano Fiandesio - Docker 101 | Codemotion Milan 2015

This document provides an overview of Docker, including its components, functionalities, and advantages over traditional virtualization. It discusses how Docker enables efficient application isolation through containers, offers automation via Dockerfiles, and supports multi-container applications with tools like Docker Compose. Additionally, it highlights the importance of Docker Hub for image sharing and registries, as well as commands for managing containers.

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DOCKER101 FROM0TODOCKERIN30MINUTES /Luciano Fiandesio @ishipsoftware
WHO'SLUCIANO Generalist 25 years of software development Consulting on lightweight approach to software factory Author of "Groovy 2 Cookbook" for Packt Dad github: https://github.com/luciano­ fiandesio
ABOUTYOU
AGENDA What is Docker Docker components Live Demo Additional resources
DOCKERSTATS 25.000 Github stars 425M+ Docker Engine downloads 100.000+ Dockerized applications on Docker Hub 180+ Docker Meetup Groups in 50 countries 950 community contributors 50.000 3rd party projects on Github using Docker in PAAS, OS, CI etc.
WHATISDOCKER? Docker vs. Virtualization
THISISWHATMAKESDOCKERSO POWERFUL
LXCCONTAINERS Available in modern kernels since 2008 Generically isolates resource usage (CPU, memory, disk, network) Guarantee resources to app/set of apps Can be adjusted on the fly Can monitor the cgroup itself to see utilization
KERNELNAMESPACES Isolating views of the system Can make a process think it’s the only process Built-in way to "virtualize" a process
KERNELNAMESPACES mnt (mount points, filesystem) pid (processes) net (network stack) ipc (inter-process comms) uts (hostname) user (UIDs)
CGROUPS-CONTROLGROUPS Built into Kernel Generically isolates resource usage (CPU, memory, disk, network) Guarantee resources to app/set of apps Can be adjusted on the fly Can monitor the cgroup itself to see utilization
WHATABOUTPERFORMANCES? Processes are isolated, but run directly on the host CPU - native performance Memory - a few % required for bean keeping Network - small overhead, can be reduced to 0
TORECAP Content Agnostic Hardware Agnostic Content Isolation Automation Highly Efficient Separation of Concerns
DOCKERCONCEPTS
DOCKERENGINE Docker is a simple client/server application A Docker client talks to a Docker daemon, which execute the work Docker executables are written in Go The Docker daemon also exposes a RESTFul API Both client and server must be executed as root!
DOCKERIMAGES Read-only templates from which containers are launched from Each image consists of a series of layers using the Union File System When an image gets modified, a new layer is created Docker can also use additional file systems
HOWDOESANIMAGELOOKLIKE? First the bootfs is loaded Then, the root fs is mounted (Ubuntu, etc) in read only mode The remaining layers are mounted Thanks to the UnionFS, the layers look like one FS Finally, when the container is launched, Docker mounts a read- write layer
THINKOFIMAGESARETHESOURCE CODEOFYOURCONTAINERS!
DOCKERCONTAINERS A container is started from an image, which may be locally created, cached locally, or downloaded from a registry It "looks & feels" like a VM Ridicolously fast boot time Low resource usage
CONTAINERS-GOODTOKNOW Containers are meant to run a single process Decouple applications into separate containers — one for each process Don’t install unnecessary packages: smaller images! Build containers that are easy to replace
DOCKERFILES Image representations Simple syntax for describing an image Automate and script the image creation Easy to learn (looks like Shell!) Fast and reliable
DOCKERFILEEXAMPLE # Version: 0.0.1 FROM ubuntu:14.04 MAINTAINER Rocky Balboa "rocky@gmail.com" RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 RUN echo 'deb http://download-distro.mongodb.org/repo/ubuntu-upstart dis RUN apt-get update # note the -y flag, for non interactive RUN apt-get install -y mongodb-org RUN mkdir -p /data/db # This mongo instance will run in a container # so it must be configured to accept connections from foreign hosts RUN echo "bind_ip = 0.0.0.0" >> /etc/mongdodb.conf EXPOSE 27017 # Set the default command for this image CMD ["mongod"]
Build the image docker build -t="balboa/mongo" .
DOCKERREGISTRY Application dedicated to the storage and distribution of your Docker images Useful when a company wants to share images internally Docker offers a commercial version, named "Docker Trusted Registry"
DOCKERHUB A cloud hosted service from Docker that provides registry capabilities for public and private content. Useful for sharing images at large or collaborating withing a team Useful for automation workflows
DOCKERMACHINE A tool to simplify the automatic creation, configuration and management of Docker- enabled machines, wheter they are VMs running locally in Virtualbox or in a cloud provider such AWS $ create --driver virtualbox dev # start machine locally using virtualbox $ create --driver digitalocean dev-cloud # start machine locally using di
DOCKERCOMPOSE A tool for running multi-container applications Single file configuration Great for dev environments, CI, staging Written in Python, was Fig (acquired by Docker) Useful for building complex environments in a reproducible way
DEMOTIME!
DOCKERCOMMANDLINE $ docker search # search hub.docker.com for an image $ docker pull # download an image $ docker images # list all existing local images $ docker run # starts a container from an image $ docker ps # list running containers $ docker build # build an image from a docker file
SOMEDOCKER'RUN'FLAGS -d # runs the container in detached mode (background proces -t # runs the container using a pseudo-tty -i # uses interactive mode --name # assign a name, instead of autogenerated one
START/KILL/REMOVECONTAINERS docker stop # stops a container docker start # starts a container docker attach # attach to a container docker remove # remove a container docker rmi # remove an image
CONTAINERSCOMMUNICATION Containers can be linked together (container linking) Container linking works well on a single host, but large-scale systems need other discovery mechanisms. $ docker run -d --name database -e MYSQL_ROOT_PASSWORD=root mysql $ docker run -d --link database:db --name web runseb/hostname $ docker run -d --link web:application --name lb nginx
CONTAINERSVOLUMES Docker can mount host voulumes in read/write mode. Data are shared between host and container $ docker run -ti -v "$PWD":/shared ubuntu:14.04 /bin/bash
ADDITIONALRESOURCES
WEJUSTSCRATCHEDTHESURFACE!
ECOSYSTEM Orchestration Clustering Discovery Cloud Monitoring Logging Security
LINKS Docker training - Docker cheat sheet - Docker cheat sheet - https://github.com/wsargent/docker-cheat-sheet More links! - http://www.nkode.io/2014/08/24/valuable- docker-links.html Docker ecosystem - mind blowing - https://www.mindmeister.com/389671722/docker- ecosystem Docker videos - http://training.docker.com/ https://github.com/wsargent/docker­cheat­ sheet https://www.youtube.com/user/dockerrun