A Gentle Introduction To Docker And All Things Containers
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This document provides a comprehensive overview of Docker and container technology, outlining its benefits for developers, operations, and management roles. It explains the architecture, functionality, and deployment strategies of Docker containers, emphasizing their efficiency and ease of use. Additionally, it discusses Docker's community, ecosystem, and roadmap for future developments.
![Authoring images
with a Dockerfile
FROM ubuntu
RUN
RUN
RUN
RUN
RUN
apt-get
apt-get
apt-get
apt-get
apt-get
-y update
install -y
install -y
install -y
install -y
g++
erlang-dev erlang-manpages erlang-base-hipe ...
libmozjs185-dev libicu-dev libtool ...
make wget
RUN wget http://.../apache-couchdb-1.3.1.tar.gz | tar -C /tmp -zxfRUN cd /tmp/apache-couchdb-* && ./configure && make install
RUN printf "[httpd]nport = 8101nbind_address = 0.0.0.0" >
/usr/local/etc/couchdb/local.d/docker.ini
EXPOSE 8101
CMD ["/usr/local/bin/couchdb"]
docker build -t jpetazzo/couchdb .](https://image.slidesharecdn.com/twilio-2013-maintalk-131115121823-phpapp02/85/A-Gentle-Introduction-To-Docker-And-All-Things-Containers-38-320.jpg)
A Gentle Introduction To Docker And All Things Containers
- 1. a Gentle Introduction to Docker and All Things Containers
- 2. Outline ● Whom is this for? ● What's the problem? ● What's a Container? ● Docker 101 ● Docker images ● Docker deployment ● Docker future
- 3. Outline ● Whom is this for? ● What's the problem? ● What's a Container? ● Docker 101 ● Docker images ● Docker deployment ● Docker future
- 4. Devs ● all languages ● all databases ● all O/S ● targetting Linux systems Docker will eventually be able to target FreeBSD, Solaris, and maybe OS X.
- 5. Ops ● any distro¹ ● any cloud² ● any machine (physical, virtual...) ● recent kernels³ ¹ as long as it's Ubuntu or Debian ☺ others coming soon ² as long as they don't ship with their custom crappy kernel ³ at least 3.8; support for RHEL 2.6.32 on the way
- 6. CFO, CIO, CTO, ... ● LESS overhead! ● MOAR consolidation! ● MOAR agility! ● LESS costs!
- 7. Outline ● Whom is this for? ● What's the problem? ● What's a Container? ● Docker 101 ● Docker images ● Docker deployment ● Docker future
- 8. The Matrix From Hell django web frontend node.js async API background workers SQL database distributed DB, big data message queue ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? staging prod on cloud VM my laptop your laptop QA prod on bare metal
- 9. Another Matrix from Hell ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
- 10. Solution: the intermodal shipping container
- 11. Solved!
- 12. Solution to the deployment problem: the Linux container
- 13. Linux containers... Units of software delivery (ship it!) ● run everywhere – – regardless of host distro – ● regardless of kernel version (but container and host architecture must match*) run anything – if it can run on the host, it can run in the container – i.e., if it can run on a Linux kernel, it can run *Unless you emulate CPU with qemu and binfmt
- 14. Outline ● Whom is this for? ● What's the problem? ● What's a Container? ● Docker 101 ● Docker images ● Docker deployment ● Docker future
- 15. High level approach: it's a lightweight VM ● own process space ● own network interface ● can run stuff as root ● can have its own /sbin/init (different from the host) « Machine Container »
- 16. Low level approach: it's chroot on steroids ● can also not have its own /sbin/init ● container = isolated process(es) ● share kernel with host ● no device emulation (neither HVM nor PV) « Application Container »
- 17. Separation of concerns: Dave the Developer ● inside my container: – my code – my libraries – my package manager – my app – my data
- 18. Separation of concerns: Oscar the Ops guy ● outside the container: – logging – remote access – network configuration – monitoring
- 19. How does it work? Isolation with namespaces ● pid ● mnt ● net ● uts ● ipc ● user
- 20. How does it work? Isolation with cgroups ● memory ● cpu ● blkio ● devices
- 21. If you're serious about security, you also need… ● capabilities – okay: cap_ipc_lock, cap_lease, cap_mknod, cap_net_admin, cap_net_bind_service, cap_net_raw – troublesome: cap_sys_admin (mount!) ● think twice before granting root ● grsec is nice ● seccomp (very specific use cases); seccomp-bpf ● beware of full-scale kernel exploits!
- 22. How does it work? Copy-on-write storage ● ● ● unioning filesystems (AUFS, overlayfs) snapshotting filesystems (BTRFS, ZFS) copy-on-write block devices (thin snapshots with LVM or device-mapper) This is now being integrated with low-level LXC tools as well!
- 23. Efficiency
- 24. Compute efficiency: almost no overhead ● ● ● ● processes are isolated, but run straight on the host CPU performance = native performance memory performance = a few % shaved off for (optional) accounting network performance = small overhead; can be reduced to zero
- 25. Storage efficiency: many options! Union Filesystems Snapshotting Filesystems Copy-on-write block devices Provisioning Superfast Supercheap Fast Cheap Fast Cheap Changing small files Changing large files Diffing Superfast Supercheap Fast Cheap Fast Costly Slow (first time) Inefficient (copy-up!) Fast Cheap Fast Cheap Superfast Superfast (ZFS) Kinda meh (BTRFS) Slow Memory usage Efficient Efficient Inefficient (at high densities) Drawbacks Random quirks AUFS not mainline !AUFS more quirks ZFS not mainline BTRFS not as nice Higher disk usage Great performance (except diffing) Bottom line Ideal for PAAS and high density things This might be the Future Dodge Ram 3500
- 26. Outline ● Whom is this for? ● What's the problem? ● What's a Container? ● Docker 101 ● Docker images ● Docker deployment ● Docker future
- 28. Docker-what? ● Open Source engine to commoditize LXC ● using copy-on-write for quick provisioning STOP! HAMMER DEMO TIME.
- 30. Yes, but... ● ● ● « I don't need Docker; I can do all that stuff with LXC tools, rsync, some scripts! » correct on all accounts; but it's also true for apt, dpkg, rpm, yum, etc. the whole point is to commoditize, i.e. make it ridiculously easy to use
- 33. What this really means… ● instead of writing « very small shell scripts » to manage containers, write them to do the rest: – continuous deployment/integration/testing – orchestration ● = use Docker as a building block ● re-use other people images (yay ecosystem!)
- 34. Docker-what? The Big Picture ● Open Source engine to commoditize LXC ● using copy-on-write for quick provisioning ● allowing to create and share images ● ● standard format for containers (stack of layers; 1 layer = tarball+metadata) standard, reproducible way to easily build trusted images (Dockerfile, Stackbrew...)
- 35. Docker-what? Under The Hood ● rewrite of dotCloud internal container engine – – ● original version: Python, tied to dotCloud's internal stuff released version: Go, legacy-free the Docker daemon runs in the background – manages containers, images, and builds – HTTP API (over UNIX or TCP socket) – embedded CLI talking to the API ● Open Source (GitHub public repository + issue tracking) ● user and dev mailing lists ● FreeNode IRC channels #docker, #docker-dev
- 36. Outline ● Whom is this for? ● What's the problem? ● What's a Container? ● Docker 101 ● Docker images ● Docker deployment ● Docker future
- 37. Authoring images with run/commit 1) docker run ubuntu bash 2) apt-get install this and that 3) docker commit <containerid> <imagename> 4) docker run <imagename> bash 5) git clone git://.../mycode 6) pip install -r requirements.txt 7) docker commit <containerid> <imagename> 8) repeat steps 4-7 as necessary 9) docker tag <imagename> <user/image> 10) docker push <user/image>
- 38. Authoring images with a Dockerfile FROM ubuntu RUN RUN RUN RUN RUN apt-get apt-get apt-get apt-get apt-get -y update install -y install -y install -y install -y g++ erlang-dev erlang-manpages erlang-base-hipe ... libmozjs185-dev libicu-dev libtool ... make wget RUN wget http://.../apache-couchdb-1.3.1.tar.gz | tar -C /tmp -zxfRUN cd /tmp/apache-couchdb-* && ./configure && make install RUN printf "[httpd]nport = 8101nbind_address = 0.0.0.0" > /usr/local/etc/couchdb/local.d/docker.ini EXPOSE 8101 CMD ["/usr/local/bin/couchdb"] docker build -t jpetazzo/couchdb .
- 39. Authoring Images with Trusted Builds 0) create a GitHub account On index.docker.io: 1) create a Docker account 2) link it with your GitHub account 3) enable Trusted Builds on any public repo On your dev env: 4) git add Dockerfile 5) git commit 6) git push
- 40. Authoring Images with Chef/Puppet/Ansible/Salt/... Plan A: « my other VM is a container » ● write a Dockerfile to install $YOUR_CM ● start tons of containers ● run $YOUR_CM in them Good if you want a mix of containers/VM/metal But slower to deploy, and uses more resources
- 41. Authoring Images with Chef/Puppet/Ansible/Salt/... Plan B: « the revolution will be containerized » ● write a Dockerfile to install $YOUR_CM ● … and run $YOUR_CM as part of build process ● deploy fully baked images Faster to deploy Easier to rollback
- 42. Outline ● Whom is this for? ● What's the problem? ● What's a Container? ● Docker 101 ● Docker images ● Docker deployment ● Docker future
- 43. Running containers ● SSH to Docker host and manual pull+run ● REST API (feel free to add SSL certs, OAUth...) ● OpenStack Nova ● OpenStack Heat ● who's next? OpenShift, CloudFoundry? ● multiple Open Source PAAS built on Docker (Cocaine, Deis, Flynn...)
- 44. Orchestration & Service Discovery (0.6.5) ● ● ● you can name your containers they get a generated name by default (red_ant, gold_monkey...) you can link your containers docker run -d -name frontdb docker run -d -link frontdb:sql frontweb → container frontweb gets one bazillion environment vars
- 45. Orchestration & Service Discovery roadmap ● ● ● currently single-host problem: how do I link with containers on other hosts? solution: ambassador pattern! – app container runs in its happy place – other things (Docker, containers...) plumb it
- 46. Orchestration roadmap ● ● ● currently static problem: what if I want to… move a container? do a master/slave failover? WebScale my MangoDB cluster? solution: dynamic discovery!
- 47. Multi-host Docker deployments More on this during my lightning talk!
- 48. Outline ● Whom is this for? ● What's the problem? ● What's a Container? ● Docker 101 ● Docker images ● Docker deployment ● Docker future
- 49. Docker: the community ● Docker: >200 contributors ● <7% of them work for dotCloud Docker inc. ● latest milestone (0.6): 40 contributors ● ~50% of all commits by external contributors ● GitHub repository: >800 forks
- 50. Docker: the ecosystem ● Cocaine (PAAS; has Docker plugin) ● CoreOS (full distro based on Docker) ● Deis (PAAS; available) ● Dokku (mini-Heroku in 100 lines of bash) ● Flynn (PAAS; in development) ● Maestro (orchestration from a simple YAML file) ● OpenStack integration (in Havana, Nova has a Docker driver) ● Pipework (high-performance, Software Defined Networks) ● Shipper (fabric-like orchestration) And many more; including SAAS offerings (Orchard, Quay...)
- 51. Docker long-term roadmap Docker 1.0: ● dynamic discovery ● remove AUFS, THINP, LXC, etc. – – storage? cp! – ● execution? chroot! we can run everywhere o/ re-add everything as plugins