11 ms·

Docker will change everything

78 points by sathishmanohar 13y ago

andyl 13y ago
Question: If I were to deploy a rails app using docker, can I put the whole stack in a single container (ruby/postgres/redis/sidekiq/etc.) Or do I need a separate container for each process?
- alfor 13y ago
  Yes, you could, but in this case it mean they will all run on the same vm and your system is going to be simpler but less flexible.
  - sneak 13y ago
    Linux containers are not virtual machines.
- jetblackio 13y ago
  I'm curious about this as well. From what I've read, it seems like it would be possible to have separate containers for each process, and then combine them together into a single container for deployment. If that works in reality, it could make it easier to mix-and-match to quickly build new applications that share some common dependencies.
- jamtur01 13y ago
  You can do both. Docker containers by default are designed to run a single process but you can use a process manager like supervisord or a script to run many too.
  - FooBarWidget 13y ago
    It's nonsense that Docker containers are designed to run a single process. There's absolutely nothing that encourages having a single process. In fact, I think you should run multiple processes because running just a single process is wrong. It will not enable many kinds of important system services, such as syslog. Take a look at https://github.com/phusion/baseimage-docker https://github.com/phusion/baseimage-docker for a full explanation. This is also the reason why I wrote baseimage-docker: to make it easy for other Docker users to get things right. I highly encourage people to use baseimage-docker.
    - pjungwir 13y ago
      I'll look at your Github repo, but is there any documentation on running multiple processes per container? The tutorials on docker.io all include just one process. And having separate ENTRYPOINT and USER directives suggests that if you want to run several things at once, they must all run as the same user.
      - FooBarWidget 13y ago
        My Github repo is the documentation. It teaches you how to run multiple processes by having them managed through runit. It even provides a script to make it easy for you to run a process as a different user. > And having separate ENTRYPOINT and USER directives suggests that if you want to run several things at once, they must all run as the same user. It does not. That's not how the Unix process model works. When you boot the Linux kernel, it also wants you to specify a single entry point. The kernel starts that process as root. Yet your Linux system clearly has multiple processes, running as different users. Why? It's because the entry point is the init system, which spawns other processes. You can do the same thing inside Docker. It's exactly the same as how your host system works! Nothing has changed!
        pjungwir 13y ago
        Okay, thank you for putting all that together. Running everything out of runit/etc is about what I figured I'd do if I wanted multiple services in one container, so it's great someone has already done all the work for me. :-)
    - jamtur01 13y ago
      Politely it's not bollocks but perhaps I should have used better wording and replaced "process" with "service". :) I look at Docker as a lightweight way of modeling infrastructure and services. I can built a shipload/stack of containers that model/mock/replicate my application architecture or my SOA model or my three tier web application. At the crudest level I can do this by modeling each host (web/app/db for example) with a container (hence single service) but it has the potential to scale up to large, clustered SOA applications too. Having that local model of my application means I am developing something that is a lot closer to reality than running a bunch of services on a shrunken set/consolidated set of hosts (or worse on my desktop) in a dev/test environment. Apologies for confusing the situation.
- finnh 13y ago
  Up to you. If it's a one-shot site that won't grow, then a single container is fine. But if you might grow, the upfront discipline of splitting them into separate containers will make it much easier to scale & distribute later. Also, while you're likely to find pre-packaged dockerfiles for each of your components, the odds are lower that you'll find an existing dockerfile that has your exact stack all-in-one. So, while the "one container" approach may save you some cross-container configuration overhead, it will likely cost you extra dockerfile creation time.
snird 13y ago
He explains the problem well, but I yet to see someone who explains the docker solution (into more details) well.
- willvarfar 13y ago
  I'll try: Previously, to control an environment for an app or set of apps, you either dictated exactly the environment os version and libraries etc, or you tried to run some kind of wrapper like fabric and virtualenv or maven or chef or whatever. And it keeps breaking for real, and developers keep screwing up because they aren't running the exact deployed system. Docker turns that around. It let's you specify the environment exactly, yet also treat that container as an app. It sorts out the versioning (git), and it makes it trivial for all devs to run the stack identically to production. As I've just had to get oracle SDK working troubleshooting on my macbook, I can't say how appealing the docker way sounds.
- jamtur01 13y ago
  This slide deck has a pretty good explanation of the solution: http://www.slideshare.net/dotCloud/why-docker2bisv4 http://www.slideshare.net/dotCloud/why-docker2bisv4
- schnevets 13y ago
  I haven't been following Docker too closely, but I think I finally made an apt metaphor from this latest article. There's an old analogy suggesting that Servers:VMs :: Houses:Apartments, as in virtualized servers are separate, individual homes from the same physical asset. With Docker, the metaphor gets extended to a dwelling with more communal space and shared resources (like a hotel or some type of commune). You have one large kitchen, one large laundry room, and a little space for any other amenities, but each room is its own unique dwelling that can utilize any and all of the external utilities. EDIT: Really, the metaphor is better if you use chroot instead of VMs
- prodigal_erik 13y ago
  It could have been clearer that the author is advocating containers as an alternative to virtual machines for isolating your apps from other users on shared servers. For some reason a lot of other people are advocating containers to isolate your apps from each other on your own server (or VM); there's very little reason to do that unless you have a bunch of poorly managed apps with incompatible dependences which didn't come from your .rpm or .deb library.
auggierose 13y ago
Nope, Docker is not going to change everything. I could tell you what is, but you won't believe me.
- DannoHung 13y ago
  I'll bite, what will change everything?
  - jetblackio 13y ago
    Haven't you heard? WolframAlpha's new language!!! http://venturebeat.com/2013/11/29/sentient-code-an-inside-look-at-stephen-wolframs-utterly-new-insanely-ambitious-computational-paradigm/ http://venturebeat.com/2013/11/29/sentient-code-an-inside-lo...
- jamtur01 13y ago
  It's flying cars isn't it? Please tell me it's flying cars.
- CmonDev 13y ago
  HN moderation?
guelo 13y ago
"self-sufficient container that will run virtually anywhere" Anywhere that is Linux.
- shykes 13y ago
  Check out boot2docker: http://github.com/steeve/boot2docker http://github.com/steeve/boot2docker It's a 25MB vm which boots a working docker installation in 5 seconds. I use it on my mac with virtualbox, and connect to it from the native docker client. That way I can run unmodified docker containers almost anywhere :)
- baddox 13y ago
  Linux runs virtually anywhere.
stox 13y ago
Yes, it will change everything...back to what it once was. You will be billed by CPU time, I/O time, network consumption, etc. Just like we did on the old Mainframes. Hopefully, this will provide the feedback loop necessary to reward efficient programming once again.
- samstave 13y ago
  BOFH is dead. Long live BOFH.
  - entendre 13y ago
    Thanks, Sid Dabster
CmonDev 13y ago
"an open source project to pack, ship and run any application as a lightweight container" - I am so excited! How exactly do I ship and run my XNA/Mono game on Android, WP, iOS?
fotcorn 13y ago
Why not just create a AWS/DigitalOcean/Rackspace instance for every service? When I need different versions of the same software I use another instance or something like Python virtualenvs.
- runako 13y ago
  Because your utilization on each of those service instances will be lower, which means that you will be paying for unused resources. The more instances you have, the larger the waste.
  - falcolas 13y ago
    Not really - overcommitting VM resources lets you get similar sharing. What docker really buys you over individual instances is lower resource overhead devoted to OS operations.
    - ithkuil 13y ago
      Sure, it's just that usually you don't control the instance sizes of <insert your favourite cloud provider here>. It's useful to be able to subslice your provisioned resources. That said, you can do it with plain LXC, no need for Docker. It's just a nice way to package components and make them run together in a predictable way and. That's the aspect I miss most from the discussion around Docker.
josh-wrale 13y ago
IMHO: On Docker, I'd say, it will change the rhetorical everything for stateless tiers. Stateful tiers will resist this change. I'm not yet comfortable upgrading to a new version of MySQL on a database using Docker in application-container mode, that is, without some package management like scripts (e.g. upgrade the dataset). For stateful tiers, full LXC containers are changing everything, at least until full full-container support arrives in Docker (because, duh, it uses LXC).
- shykes 13y ago
  > at least until full full-container support arrives in Docker If by "full-container" you mean booting a full /sbin/init in a container, Docker supports that. Just 'docker run /sbin/init' :) > I'm not yet comfortable upgrading to a new version of MySQL on a database using Docker Check out volume sharing `docker run -volumes-from`, it allows you to share the same data volumes between several containers. You can use that primitive to upgrade a database, as well as to run short-lived jobs which affect the dataset: migrations, backups etc.
  - josh-wrale 13y ago
    Thank you shykes. I didn't know about the volume sharing. It sounds cool, but I'll need to think more about how such a workflow might work in production. My initial thought is that such a database upgrade would be considerably more difficult to coordinate than say a yum/apt package upgrade. This is unfortunate but it's not entirely a deal breaker (with proper DevOps, anyway). The full container concept is only partially implemented it seems, per the issues linked below. Parity with LXC for a more full VM-like experience would definitely motivate me to adopt Docker quicker in more places (e.g. stateful tiers). Any chance these issues could be given high priority? https://github.com/dotcloud/docker/issues/1960 https://github.com/dotcloud/docker/issues/1960 https://github.com/dotcloud/docker/issues/2276 https://github.com/dotcloud/docker/issues/2276 Thanks, Joshua
vpsserver 13y ago
> lightweight, portable, self-sufficient container that will run virtually anywhere. It doesn't work on typical cheap VPS servers from http://lowendbox.com/ http://lowendbox.com/ because they use OpenVZ.
- Joeboy 13y ago
  That's where I found the cheap (5gbp per month from NECS) VPS I run my docker instances on. Maybe it is atypical.
  - supergauntlet 13y ago
    It'll certainly work with a cheap Xen or KVM instance but those are usually more expensive.
- aufreak3 13y ago
  Digitalocean has a standard docker+ubuntu setup you can fire up for about that price. However, I haven't had much luck with its stability and switched back to running on bare ubuntu. Docker kept bringing the system down even when I wasnt running any containers!
- wmf 13y ago
  Long-term I expect cheap VPSes to be built on Docker itself because it's more upstream than OpenVZ.
  - deleted 13y ago
    [deleted]
xacaxulu 13y ago
IT WILL CHANGE EVERYTHING!!! Including orbits of small moons around planets we haven't discovered yet.
andrewfong 13y ago
Can someone comment on what I would use Docker for as opposed to what I would use Chef / Puppet / Ansible for?
- Sikul 13y ago
  You don't have to use one or the other. Docker is more about shipping around images that can be used to start containers. How you configure the image is up to you, but Docker provides a "Dockerfile" that can configure images with bash commands. You can call Chef / Puppet / Ansible from the Dockerfile to configure the image. Once the image is created you can send it out to any machine that has docker installed and start it up.
- rdtsc 13y ago
  Docker is a very lightweight VM. Or a much nicer chroot. However you want to look at it. The underlying technology is LXC. It is very cool stuff. But the top article is full of bullshit. It doesn't run "virtually anywhere", it runs on a few systems that support LXC or you have to build a VM that does support LXC, so you can host your Docker VM, inside that VM. How does that "Yo Dog" meme go...?
  - jpetazzo 13y ago
    "A few systems that support LXC", that's actually most modern Linux systems now. Anything with a 3.8 kernel is game.
    - rdtsc 13y ago
      > that's actually most modern Linux systems now. Anything with a 3.8 kernel is game. So Linux systems, that started shipping just this year? Well but even that is not true because it was backport-ed to RHEL 6/CentOS 6 which is very cool. Not all people live dangerously and install the very latest release on their server. Ubuntu LTS (which is a common server platform) also doesn't natively support LXC well. It has an older kernel. So instructions for installing docker is to install a new kernel. A new custom compiled kernel on a production system. Hmm, is that still Ubuntu 12.04 LTS, some devops will argue it isn't, some will say it is fine.
siliconc0w 13y ago
I still think there needs to be a bridge for SCM tools and Docker. Docker allows you to easily share an enviornmnet but there is still value in documenting how that environment was built - preferably via a flexible language (chef/puppet/ansible) instead of just sequential bash commands. Is there already a project out there that does docker-based continuous integration?
- jzila 13y ago
  Yes, Seattle-based Shippable, which announced over $2M in funding yesterday. https://www.shippable.com/ https://www.shippable.com/ http://techcrunch.com/2013/12/10/techstars-seattle-startup-shippable-raises-2-05m-for-continuous-integration-platform-built-on-docker/ http://techcrunch.com/2013/12/10/techstars-seattle-startup-s...
- shykes 13y ago
  Docker does this. * With docker build you can automate the building of a docker container from source. Simply add a Dockerfile to your source to specify exactly how to assemble it, step by step. This can be done with the high-level build or configuration tool of your choice. * With docker history you can point to any docker container and get a full record of exactly how it was built. * We are adding image signature to allow verification of the origin of any particular container image.
  - AjithAntony 13y ago
    Do you literally mean from source, or from a base image? If I understand correctly, this is only up to the base image. All the docker docs talk about basing images from well known images from the index. I'd very much like to know how "ubuntu" is prepared for example.
    - shykes 13y ago
      Yes, I literally mean from source. The source, in turn, can either 1) specify a base image to start from (keeping in mind the base image can recursively be itself built from source), or 2) start from scratch and contain all the starting bits. Of course there is always a "turtle at the bottom". That problem exists regardless of Docker - for example when you download binary packages from an apt mirror, that package has been built from source - but on which build environment exactly, with which build dependencies etc? Docker simply makes this question more explicit by forcing you to ask that question every step of the way - what is the base? - instead of sweeping it under the rug, which we do every day when we install binary packages. What we're doing for the docker standard library is exposing exactly what the turtles at the bottom are: https://github.com/dotcloud/stackbrew/tree/master/library https://github.com/dotcloud/stackbrew/tree/master/library
jamra 13y ago
How do you scale with Docker? I get the idea of how containers work. I get the idea of how it shares resources between like containers. That's all very cool. My question is how do I scale a docker container? It's not well covered in the tutorial. Do I just add more containers? What happens when I want to scale on separate servers? I don't see any configurability of the items inside the containers.
- nickstinemates 13y ago
  > Do I just add more containers Yep > Sepeate servers? Today, manual. Docker Host clustering is a feature that needs to be worked out. > Configurability of items inside of containers The `link` primitive in the 0.7 release is the key to this one. While primitive currently, it's already extremely powerful and will only get better.
  - jamra 13y ago
    Thank you.
    - nickstinemates 13y ago
      Anytime :) This is what I do, so please don't hesitate.
- wmf 13y ago
  For scaling you probably want to use a Docker-based PaaS like Flynn or Deis. I would propose starting with vertical scaling by increasing cgroup limits on a single container and once the container can't grow any more you can scale horizontally by adding more containers on other machine.
tomrod 13y ago
I'd love to understand what use cases Docker is used for. I read a lot of comments where people talk about outsourcing functions their laptop would normally run, but I'm not sure of the comparative advantages of that method. I wonder a few things: 1. Could tighter security be implemented by outsourcing certain functions to Docker--the base computation can only allow certain routines to run, for example, disallowing any trojan activity? (Similar to blocking ports, but at an IO or computing level). 2. How is this tech beneficial to the consumer market? As the consumer market goes the business market (as we saw in Microsoft/Apple/iOS adoption--consumers demanded it then wanted to use it in business situations) 3. Is the tech Docker using propietary, trade secret, or protected by patent? In our current environment tech firms face terrible regulatory uncertainty due to crappy patents. Can a viable competitor to Docker exist?
- nickstinemates 13y ago
  > Use cases Continuous Integration / Delivery / Deployment, Embedded systems, Software/Service Distribution, PaaS, SaaS.. A shorter list would be what use cases is Docker not a candidate for? > Beneficial to consumers Efficient Ops allows for innovation to reach consumers faster and more often. > Proprietary? Nope. Docker is open source and open design. Want to change the direction of the project? Open a pull request and get 2 core maintainers to agree. Want to change those rules? Open a pull request to change project governance and get 2 core maintainers to agree.
  - tomrod 13y ago
    > Efficient Ops allows for innovation to reach consumers faster and more often. So I have an IRC channel I can contact the developers at all time, and rollout of upgrades is automated? That's good I guess, but hardly groundbreaking. If I'm Joe C. ComputerUser with Windows XP running on a circa 2007 Thinkpad, what is Docker and why do I need it? Good to hear it's open source.
    - nickstinemates 13y ago
      If you're Joe C. ComputerUser with Windows XP you're likely consuming services that are powered by Docker. That's the 'consumer benefit' Docker isn't Excel or Word or Some 15 year old game. It's server-oriented software/technology and thus, from a usage standpoint, targeting that community.
Kiro 13y ago
>But what happens when there is another rails application that uses the same stack. you need to setup another instance identical to the previous one to run the second application in production. Why not just run them on the same "instance"? What does instance even refer to?
- sathishmanohar 13y ago
  Multiple applications can be run on same "instance" using some configuration, but for a elastic setup which requires to spin up and down instances according to demand, Its not a viable option. Since, it complicates things too much, which is why I haven't mentioned that in the article.
rdtsc 13y ago
> automates the deployment of any application as a lightweight, portable, self-sufficient container that will run virtually anywhere. Bullshit. How do I run it on RHEL 5, because DoD systems are chock full of those? What about Windows? I have to install Virtualbox, and Vagrant and then run Docker inside the virtualized linux environment and then run docker containers in that. So "virtually anywhere" means on a handful of systems. Sometimes technology's biggest "fans" are its biggest enemies without even realizing.
- Aqueous 13y ago
  I really wish Apple, for instance, would enable the same process/network namespacing that enables LXC to work. I'm not sure what the state of Windows is with respect to virtual network namespaces and process namespaces and control groups, but if the two other major OSes enable these basic features, it is easy to imagine universal containers that run everywhere.
  - rdtsc 13y ago
    Apple could choose to support LXC. FreeBSD systems have jails, so another way forward was if Apple support that, Docker could wrap a generic API on top of that. Much like libvirt is doing with various VM hosting solutions.
    - nickstinemates 13y ago
      Or Docker could gracefully degrade to using chroot on OS X (providing a different type of isolation.) This is a plan. One of the things Docker needs to get better at expressing is that A Docker container != Linux Containers. It may currently Build/Provision/Execute inside of a Linux Container (provided by LXC) but that is an (albeit important) implementation detail.
- kulkarnic 13y ago
  That is unnecessarily harsh. Docker legitimately represents a new idea, and some claim, a better idea. Yes, it won't run on RHEL5; but Java probably did not run on DEC mainframes either (back when its selling point was Write once run anywhere). The question seems to be this: does this container model represent a step forward? I think it does. (And is it hyped a bit too much? Probably :-)
mey 13y ago
FreeBSD jail isn't dead yet.
steeve 13y ago
Hey folks, if you want to try out Docker easily, you use https://github.com/steeve/boot2docker https://github.com/steeve/boot2docker It's a 23mb ISO that boots in 6s and allows you to get started right away.
pjungwir 13y ago
Docker sounds very interesting, but I have a ton of questions. I'm very familiar with Chef and Vagrant, and passingly familiar with FreeBSD jails, but I'm having trouble wrapping my head around Docker. Here are some questions: - Why use ENTRYPOINT rather than init.d scripts? - When I'm building the Dockerfile, how do I do something like `vi /etc/apache2/sites-available/my-app`? In other words, how do I drop a whole config file onto the image, the way I'd use Chef files/templates? - Is it possible to parameterize a Dockerfile, so people can use my image but adjust the nginx timeout time? - Do Dockerfile commands need to be idempotent? For example will this cause problems?: `RUN echo "deb http://archive.ubuntu.com/ubuntu http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list` - If I'm using docker to host Rails-on-unicorn, do I still use Capistrano to push a new deploy, or do I spin down the whole docker container then launch another with my latest code? If the latter, are there any existing tools for that?
- calgaryeng 13y ago
  If you get the answers to these questions, could you please let me know??? calgaryeng[at]hotmail.com

andyl 13y ago

Question: If I were to deploy a rails app using docker, can I put the whole stack in a single container (ruby/postgres/redis/sidekiq/etc.) Or do I need a separate container for each process?

alfor 13y ago
Yes, you could, but in this case it mean they will all run on the same vm and your system is going to be simpler but less flexible.
- sneak 13y ago
  Linux containers are not virtual machines.
jetblackio 13y ago
I'm curious about this as well. From what I've read, it seems like it would be possible to have separate containers for each process, and then combine them together into a single container for deployment. If that works in reality, it could make it easier to mix-and-match to quickly build new applications that share some common dependencies.
jamtur01 13y ago
You can do both. Docker containers by default are designed to run a single process but you can use a process manager like supervisord or a script to run many too.
- FooBarWidget 13y ago
  It's nonsense that Docker containers are designed to run a single process. There's absolutely nothing that encourages having a single process. In fact, I think you should run multiple processes because running just a single process is wrong. It will not enable many kinds of important system services, such as syslog. Take a look at https://github.com/phusion/baseimage-docker https://github.com/phusion/baseimage-docker for a full explanation. This is also the reason why I wrote baseimage-docker: to make it easy for other Docker users to get things right. I highly encourage people to use baseimage-docker.
  - pjungwir 13y ago
    I'll look at your Github repo, but is there any documentation on running multiple processes per container? The tutorials on docker.io all include just one process. And having separate ENTRYPOINT and USER directives suggests that if you want to run several things at once, they must all run as the same user.
    - FooBarWidget 13y ago
      My Github repo is the documentation. It teaches you how to run multiple processes by having them managed through runit. It even provides a script to make it easy for you to run a process as a different user. > And having separate ENTRYPOINT and USER directives suggests that if you want to run several things at once, they must all run as the same user. It does not. That's not how the Unix process model works. When you boot the Linux kernel, it also wants you to specify a single entry point. The kernel starts that process as root. Yet your Linux system clearly has multiple processes, running as different users. Why? It's because the entry point is the init system, which spawns other processes. You can do the same thing inside Docker. It's exactly the same as how your host system works! Nothing has changed!
      - pjungwir 13y ago
        Okay, thank you for putting all that together. Running everything out of runit/etc is about what I figured I'd do if I wanted multiple services in one container, so it's great someone has already done all the work for me. :-)
  - jamtur01 13y ago
    Politely it's not bollocks but perhaps I should have used better wording and replaced "process" with "service". :) I look at Docker as a lightweight way of modeling infrastructure and services. I can built a shipload/stack of containers that model/mock/replicate my application architecture or my SOA model or my three tier web application. At the crudest level I can do this by modeling each host (web/app/db for example) with a container (hence single service) but it has the potential to scale up to large, clustered SOA applications too. Having that local model of my application means I am developing something that is a lot closer to reality than running a bunch of services on a shrunken set/consolidated set of hosts (or worse on my desktop) in a dev/test environment. Apologies for confusing the situation.
finnh 13y ago
Up to you. If it's a one-shot site that won't grow, then a single container is fine. But if you might grow, the upfront discipline of splitting them into separate containers will make it much easier to scale & distribute later. Also, while you're likely to find pre-packaged dockerfiles for each of your components, the odds are lower that you'll find an existing dockerfile that has your exact stack all-in-one. So, while the "one container" approach may save you some cross-container configuration overhead, it will likely cost you extra dockerfile creation time.

snird 13y ago

He explains the problem well, but I yet to see someone who explains the docker solution (into more details) well.

willvarfar 13y ago
I'll try: Previously, to control an environment for an app or set of apps, you either dictated exactly the environment os version and libraries etc, or you tried to run some kind of wrapper like fabric and virtualenv or maven or chef or whatever. And it keeps breaking for real, and developers keep screwing up because they aren't running the exact deployed system. Docker turns that around. It let's you specify the environment exactly, yet also treat that container as an app. It sorts out the versioning (git), and it makes it trivial for all devs to run the stack identically to production. As I've just had to get oracle SDK working troubleshooting on my macbook, I can't say how appealing the docker way sounds.
jamtur01 13y ago
This slide deck has a pretty good explanation of the solution: http://www.slideshare.net/dotCloud/why-docker2bisv4 http://www.slideshare.net/dotCloud/why-docker2bisv4
schnevets 13y ago
I haven't been following Docker too closely, but I think I finally made an apt metaphor from this latest article. There's an old analogy suggesting that Servers:VMs :: Houses:Apartments, as in virtualized servers are separate, individual homes from the same physical asset. With Docker, the metaphor gets extended to a dwelling with more communal space and shared resources (like a hotel or some type of commune). You have one large kitchen, one large laundry room, and a little space for any other amenities, but each room is its own unique dwelling that can utilize any and all of the external utilities. EDIT: Really, the metaphor is better if you use chroot instead of VMs
prodigal_erik 13y ago
It could have been clearer that the author is advocating containers as an alternative to virtual machines for isolating your apps from other users on shared servers. For some reason a lot of other people are advocating containers to isolate your apps from each other on your own server (or VM); there's very little reason to do that unless you have a bunch of poorly managed apps with incompatible dependences which didn't come from your .rpm or .deb library.

auggierose 13y ago

Nope, Docker is not going to change everything. I could tell you what is, but you won't believe me.

DannoHung 13y ago
I'll bite, what will change everything?
- jetblackio 13y ago
  Haven't you heard? WolframAlpha's new language!!! http://venturebeat.com/2013/11/29/sentient-code-an-inside-look-at-stephen-wolframs-utterly-new-insanely-ambitious-computational-paradigm/ http://venturebeat.com/2013/11/29/sentient-code-an-inside-lo...
jamtur01 13y ago
It's flying cars isn't it? Please tell me it's flying cars.
CmonDev 13y ago
HN moderation?

guelo 13y ago

"self-sufficient container that will run virtually anywhere" Anywhere that is Linux.

shykes 13y ago
Check out boot2docker: http://github.com/steeve/boot2docker http://github.com/steeve/boot2docker It's a 25MB vm which boots a working docker installation in 5 seconds. I use it on my mac with virtualbox, and connect to it from the native docker client. That way I can run unmodified docker containers almost anywhere :)
baddox 13y ago
Linux runs virtually anywhere.

stox 13y ago

Yes, it will change everything...back to what it once was. You will be billed by CPU time, I/O time, network consumption, etc. Just like we did on the old Mainframes. Hopefully, this will provide the feedback loop necessary to reward efficient programming once again.

samstave 13y ago
BOFH is dead. Long live BOFH.
- entendre 13y ago
  Thanks, Sid Dabster

CmonDev 13y ago

"an open source project to pack, ship and run any application as a lightweight container" - I am so excited! How exactly do I ship and run my XNA/Mono game on Android, WP, iOS?

fotcorn 13y ago

Why not just create a AWS/DigitalOcean/Rackspace instance for every service? When I need different versions of the same software I use another instance or something like Python virtualenvs.

runako 13y ago
Because your utilization on each of those service instances will be lower, which means that you will be paying for unused resources. The more instances you have, the larger the waste.
- falcolas 13y ago
  Not really - overcommitting VM resources lets you get similar sharing. What docker really buys you over individual instances is lower resource overhead devoted to OS operations.
  - ithkuil 13y ago
    Sure, it's just that usually you don't control the instance sizes of <insert your favourite cloud provider here>. It's useful to be able to subslice your provisioned resources. That said, you can do it with plain LXC, no need for Docker. It's just a nice way to package components and make them run together in a predictable way and. That's the aspect I miss most from the discussion around Docker.

josh-wrale 13y ago

IMHO: On Docker, I'd say, it will change the rhetorical everything for stateless tiers. Stateful tiers will resist this change. I'm not yet comfortable upgrading to a new version of MySQL on a database using Docker in application-container mode, that is, without some package management like scripts (e.g. upgrade the dataset). For stateful tiers, full LXC containers are changing everything, at least until full full-container support arrives in Docker (because, duh, it uses LXC).

shykes 13y ago
> at least until full full-container support arrives in Docker If by "full-container" you mean booting a full /sbin/init in a container, Docker supports that. Just 'docker run /sbin/init' :) > I'm not yet comfortable upgrading to a new version of MySQL on a database using Docker Check out volume sharing `docker run -volumes-from`, it allows you to share the same data volumes between several containers. You can use that primitive to upgrade a database, as well as to run short-lived jobs which affect the dataset: migrations, backups etc.
- josh-wrale 13y ago
  Thank you shykes. I didn't know about the volume sharing. It sounds cool, but I'll need to think more about how such a workflow might work in production. My initial thought is that such a database upgrade would be considerably more difficult to coordinate than say a yum/apt package upgrade. This is unfortunate but it's not entirely a deal breaker (with proper DevOps, anyway). The full container concept is only partially implemented it seems, per the issues linked below. Parity with LXC for a more full VM-like experience would definitely motivate me to adopt Docker quicker in more places (e.g. stateful tiers). Any chance these issues could be given high priority? https://github.com/dotcloud/docker/issues/1960 https://github.com/dotcloud/docker/issues/1960 https://github.com/dotcloud/docker/issues/2276 https://github.com/dotcloud/docker/issues/2276 Thanks, Joshua

vpsserver 13y ago

> lightweight, portable, self-sufficient container that will run virtually anywhere. It doesn't work on typical cheap VPS servers from http://lowendbox.com/ http://lowendbox.com/ because they use OpenVZ.

Joeboy 13y ago
That's where I found the cheap (5gbp per month from NECS) VPS I run my docker instances on. Maybe it is atypical.
- supergauntlet 13y ago
  It'll certainly work with a cheap Xen or KVM instance but those are usually more expensive.
aufreak3 13y ago
Digitalocean has a standard docker+ubuntu setup you can fire up for about that price. However, I haven't had much luck with its stability and switched back to running on bare ubuntu. Docker kept bringing the system down even when I wasnt running any containers!
wmf 13y ago
Long-term I expect cheap VPSes to be built on Docker itself because it's more upstream than OpenVZ.
- deleted 13y ago
  [deleted]

xacaxulu 13y ago

IT WILL CHANGE EVERYTHING!!! Including orbits of small moons around planets we haven't discovered yet.

andrewfong 13y ago

Can someone comment on what I would use Docker for as opposed to what I would use Chef / Puppet / Ansible for?

Sikul 13y ago
You don't have to use one or the other. Docker is more about shipping around images that can be used to start containers. How you configure the image is up to you, but Docker provides a "Dockerfile" that can configure images with bash commands. You can call Chef / Puppet / Ansible from the Dockerfile to configure the image. Once the image is created you can send it out to any machine that has docker installed and start it up.
rdtsc 13y ago
Docker is a very lightweight VM. Or a much nicer chroot. However you want to look at it. The underlying technology is LXC. It is very cool stuff. But the top article is full of bullshit. It doesn't run "virtually anywhere", it runs on a few systems that support LXC or you have to build a VM that does support LXC, so you can host your Docker VM, inside that VM. How does that "Yo Dog" meme go...?
- jpetazzo 13y ago
  "A few systems that support LXC", that's actually most modern Linux systems now. Anything with a 3.8 kernel is game.
  - rdtsc 13y ago
    > that's actually most modern Linux systems now. Anything with a 3.8 kernel is game. So Linux systems, that started shipping just this year? Well but even that is not true because it was backport-ed to RHEL 6/CentOS 6 which is very cool. Not all people live dangerously and install the very latest release on their server. Ubuntu LTS (which is a common server platform) also doesn't natively support LXC well. It has an older kernel. So instructions for installing docker is to install a new kernel. A new custom compiled kernel on a production system. Hmm, is that still Ubuntu 12.04 LTS, some devops will argue it isn't, some will say it is fine.

siliconc0w 13y ago

I still think there needs to be a bridge for SCM tools and Docker. Docker allows you to easily share an enviornmnet but there is still value in documenting how that environment was built - preferably via a flexible language (chef/puppet/ansible) instead of just sequential bash commands. Is there already a project out there that does docker-based continuous integration?

jzila 13y ago
Yes, Seattle-based Shippable, which announced over $2M in funding yesterday. https://www.shippable.com/ https://www.shippable.com/ http://techcrunch.com/2013/12/10/techstars-seattle-startup-shippable-raises-2-05m-for-continuous-integration-platform-built-on-docker/ http://techcrunch.com/2013/12/10/techstars-seattle-startup-s...
shykes 13y ago
Docker does this. * With docker build you can automate the building of a docker container from source. Simply add a Dockerfile to your source to specify exactly how to assemble it, step by step. This can be done with the high-level build or configuration tool of your choice. * With docker history you can point to any docker container and get a full record of exactly how it was built. * We are adding image signature to allow verification of the origin of any particular container image.
- AjithAntony 13y ago
  Do you literally mean from source, or from a base image? If I understand correctly, this is only up to the base image. All the docker docs talk about basing images from well known images from the index. I'd very much like to know how "ubuntu" is prepared for example.
  - shykes 13y ago
    Yes, I literally mean from source. The source, in turn, can either 1) specify a base image to start from (keeping in mind the base image can recursively be itself built from source), or 2) start from scratch and contain all the starting bits. Of course there is always a "turtle at the bottom". That problem exists regardless of Docker - for example when you download binary packages from an apt mirror, that package has been built from source - but on which build environment exactly, with which build dependencies etc? Docker simply makes this question more explicit by forcing you to ask that question every step of the way - what is the base? - instead of sweeping it under the rug, which we do every day when we install binary packages. What we're doing for the docker standard library is exposing exactly what the turtles at the bottom are: https://github.com/dotcloud/stackbrew/tree/master/library https://github.com/dotcloud/stackbrew/tree/master/library

jamra 13y ago

How do you scale with Docker? I get the idea of how containers work. I get the idea of how it shares resources between like containers. That's all very cool. My question is how do I scale a docker container? It's not well covered in the tutorial. Do I just add more containers? What happens when I want to scale on separate servers? I don't see any configurability of the items inside the containers.

nickstinemates 13y ago
> Do I just add more containers Yep > Sepeate servers? Today, manual. Docker Host clustering is a feature that needs to be worked out. > Configurability of items inside of containers The `link` primitive in the 0.7 release is the key to this one. While primitive currently, it's already extremely powerful and will only get better.
- jamra 13y ago
  Thank you.
  - nickstinemates 13y ago
    Anytime :) This is what I do, so please don't hesitate.
wmf 13y ago
For scaling you probably want to use a Docker-based PaaS like Flynn or Deis. I would propose starting with vertical scaling by increasing cgroup limits on a single container and once the container can't grow any more you can scale horizontally by adding more containers on other machine.

tomrod 13y ago

I'd love to understand what use cases Docker is used for. I read a lot of comments where people talk about outsourcing functions their laptop would normally run, but I'm not sure of the comparative advantages of that method. I wonder a few things: 1. Could tighter security be implemented by outsourcing certain functions to Docker--the base computation can only allow certain routines to run, for example, disallowing any trojan activity? (Similar to blocking ports, but at an IO or computing level). 2. How is this tech beneficial to the consumer market? As the consumer market goes the business market (as we saw in Microsoft/Apple/iOS adoption--consumers demanded it then wanted to use it in business situations) 3. Is the tech Docker using propietary, trade secret, or protected by patent? In our current environment tech firms face terrible regulatory uncertainty due to crappy patents. Can a viable competitor to Docker exist?

nickstinemates 13y ago
> Use cases Continuous Integration / Delivery / Deployment, Embedded systems, Software/Service Distribution, PaaS, SaaS.. A shorter list would be what use cases is Docker not a candidate for? > Beneficial to consumers Efficient Ops allows for innovation to reach consumers faster and more often. > Proprietary? Nope. Docker is open source and open design. Want to change the direction of the project? Open a pull request and get 2 core maintainers to agree. Want to change those rules? Open a pull request to change project governance and get 2 core maintainers to agree.
- tomrod 13y ago
  > Efficient Ops allows for innovation to reach consumers faster and more often. So I have an IRC channel I can contact the developers at all time, and rollout of upgrades is automated? That's good I guess, but hardly groundbreaking. If I'm Joe C. ComputerUser with Windows XP running on a circa 2007 Thinkpad, what is Docker and why do I need it? Good to hear it's open source.
  - nickstinemates 13y ago
    If you're Joe C. ComputerUser with Windows XP you're likely consuming services that are powered by Docker. That's the 'consumer benefit' Docker isn't Excel or Word or Some 15 year old game. It's server-oriented software/technology and thus, from a usage standpoint, targeting that community.

Kiro 13y ago

>But what happens when there is another rails application that uses the same stack. you need to setup another instance identical to the previous one to run the second application in production. Why not just run them on the same "instance"? What does instance even refer to?

sathishmanohar 13y ago
Multiple applications can be run on same "instance" using some configuration, but for a elastic setup which requires to spin up and down instances according to demand, Its not a viable option. Since, it complicates things too much, which is why I haven't mentioned that in the article.

rdtsc 13y ago

> automates the deployment of any application as a lightweight, portable, self-sufficient container that will run virtually anywhere. Bullshit. How do I run it on RHEL 5, because DoD systems are chock full of those? What about Windows? I have to install Virtualbox, and Vagrant and then run Docker inside the virtualized linux environment and then run docker containers in that. So "virtually anywhere" means on a handful of systems. Sometimes technology's biggest "fans" are its biggest enemies without even realizing.

Aqueous 13y ago
I really wish Apple, for instance, would enable the same process/network namespacing that enables LXC to work. I'm not sure what the state of Windows is with respect to virtual network namespaces and process namespaces and control groups, but if the two other major OSes enable these basic features, it is easy to imagine universal containers that run everywhere.
- rdtsc 13y ago
  Apple could choose to support LXC. FreeBSD systems have jails, so another way forward was if Apple support that, Docker could wrap a generic API on top of that. Much like libvirt is doing with various VM hosting solutions.
  - nickstinemates 13y ago
    Or Docker could gracefully degrade to using chroot on OS X (providing a different type of isolation.) This is a plan. One of the things Docker needs to get better at expressing is that A Docker container != Linux Containers. It may currently Build/Provision/Execute inside of a Linux Container (provided by LXC) but that is an (albeit important) implementation detail.
kulkarnic 13y ago
That is unnecessarily harsh. Docker legitimately represents a new idea, and some claim, a better idea. Yes, it won't run on RHEL5; but Java probably did not run on DEC mainframes either (back when its selling point was Write once run anywhere). The question seems to be this: does this container model represent a step forward? I think it does. (And is it hyped a bit too much? Probably :-)

mey 13y ago

FreeBSD jail isn't dead yet.

steeve 13y ago

Hey folks, if you want to try out Docker easily, you use https://github.com/steeve/boot2docker https://github.com/steeve/boot2docker It's a 23mb ISO that boots in 6s and allows you to get started right away.

pjungwir 13y ago

Docker sounds very interesting, but I have a ton of questions. I'm very familiar with Chef and Vagrant, and passingly familiar with FreeBSD jails, but I'm having trouble wrapping my head around Docker. Here are some questions: - Why use ENTRYPOINT rather than init.d scripts? - When I'm building the Dockerfile, how do I do something like `vi /etc/apache2/sites-available/my-app`? In other words, how do I drop a whole config file onto the image, the way I'd use Chef files/templates? - Is it possible to parameterize a Dockerfile, so people can use my image but adjust the nginx timeout time? - Do Dockerfile commands need to be idempotent? For example will this cause problems?: `RUN echo "deb http://archive.ubuntu.com/ubuntu http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list` - If I'm using docker to host Rails-on-unicorn, do I still use Capistrano to push a new deploy, or do I spin down the whole docker container then launch another with my latest code? If the latter, are there any existing tools for that?

calgaryeng 13y ago
If you get the answers to these questions, could you please let me know??? calgaryeng[at]hotmail.com