16 ms·

Ask HN: Why is Docker so popular in comparison to other containerization tech?

144 points by justaj 9y ago

Has it only been the first mover effect or are there (decisive) features that other technologies don't have?

asimpletune 9y ago
It depends on what you mean by Docker. As a container, it’s adds a lot of conveniences, despite that at the end of the day it all boils down to cgroups and namespaces. If you mean as a container orchestrator, I have no idea. Honestly Mesos seems much better than Docker or Kube in this regard. It scales better, is more reliable, and is more flexible. The one downside as I see it is there’s a steeper learning curve.
spoksmustache 9y ago
Because they spent two hundred million dollars promoting it.
- jacques_chester 9y ago
  They raised the money after, and largely because, it had popular groundswell amongst developers.
williamstein 9y ago
My guesses: Docker has been around a while, is mature and is battle tested; it was a bit ahead of other options when critical adoption decisions were being made. I remember using LXC in Debian (and Ubuntu) around 2013 and hitting a lot of disturbing bugs, due to immaturity...
- user5994461 9y ago
  It's not mature and not battle tested. There is barely anyone using it. They few who do are walking on eggs. it's hardly possible to find two experiments running the same ecosystem between all the distributions and the commercial services. Centos, Debian, RedHat, CoreOS, kubernetes, AWS ECS, Google container, cloud foundry, openshift...
minitech 9y ago
Can you list some alternatives you’d like to see it compared to?
- justaj 9y ago
  Sure: - LXC - Rkt - *BSD jails
gomangogo 9y ago
Because it is robust and lightweight. It tackled all the facets of apps isolation.
- gaius 9y ago
  It most certainly does not. If you are using Docker containers for security or QoS you're doing it wrong, and I think even Docker the company would concur. It's a fantastic packaging and deployment format, but it's not a universal solution.
  - BrandoElFollito 9y ago
    Do you have any current sources for the security part? Everything I read is along the lines of "this is not secure, we think, but do not have any specific examples. But be careful"
    - gaius 9y ago
      https://news.ycombinator.com/item?id=16030107 https://news.ycombinator.com/item?id=16030107
directionless 9y ago
It's got a good name, and was an early mover in the field.
- TheDong 9y ago
  lxc and jails are both good names (in fact, I think bsd jails is the best name of those). lxc and jails both predate docker by quite a while.
  - TheRealPomax 9y ago
    Jails is an absolutely terrible name when you need to sell your company, rather than your friends, on using this technology. "Pff, yeah right, no one rejects a technology just because the name has negative connotation in a different context", except that is literally what happens.
    - megaman22 9y ago
      Ah, the cockroachdb argument. We're rapidly approaching the point where any meaningful names are already in use, and everything uses nonsense names anyway.
      - TheRealPomax 9y ago
        Nonsense names are great, like "MySQL" or "Kubernetes". Names that the people you're trying to sell it to recognize from normal language like "jails", "cockroachdb", not so much. If you're in a startup and you need to sell it to your CTO: whatever. If you're in a 2k+ employee company and you need to sell it to general management: you are not going to be using jails, or cockroachdbs, or anything else that makes non-tech people raise their eyebrows in the bad way when they hear/read them.
        stevesimmons 9y ago
        Kubernetes isn't a nonsense name. Κυβερνήτης is Ancient Greek for helmsman. Which is not unrelated to Docker.
maxaf 9y ago
What other containerization technologies?
- peterkelly 9y ago
  - chroot - Zones (Solaris) - Jails (FreeBSD) - OpenVZ (Linux) - LXC (Linux) - VServer (Linux) - lmctfy (Linux) - WPARs (AIX) ... and more; see https://en.wikipedia.org/wiki/Operating-system-level_virtualization https://en.wikipedia.org/wiki/Operating-system-level_virtual...
  - djsumdog 9y ago
    Most people use LXC to run containers that run full operating systems right? (Where it loads init/systemd and then processes .. basically a full VM but lightweight?) The others are all more single process isolated, but how many others have the image building/hashing/layering system of Docker. I personally wish Docker was more of a first class citizen on FreeBSD, but the official port was way out of date the last time I checked.
  - m1keil 9y ago
    I'm not sure about the rest but OpenVZ never got into mainline kernel and required custom extensions while Docker did not. It's probably very contributing factor.
  - xorcist 9y ago
    Probably should add systemd-nspawn to that list. Regular systemd that you probably need to know how to use anyway can launch things in namespaces and even use common image formats. Very useful.
  - drdaeman 9y ago
    Docker images is a simple quick-and-dirty packaging solution with all the pieces necessary (building, versioning, storage and deployment). I believe this is why it won. Don't think any of those other options had anything similar. The alternatives, like building and deploying apps with native OS packages (e.g. .debs) were significantly more complicated and less portable. (While it's not that Docker images are better than native packages, they're doubtlessly generally easier.)
westoque 9y ago
I came from using Vagrant at a previous company and from my experience, Docker is just more lightweight, portable, and user friendly. Share a file/folder? Expose a port? Get an image and run a container? You can do it easily using Docker cli. You want a UI tool that makes that task even easier for you, get Kitematic. Also, Docker just has more development and maturity at this stage that it makes deployments easier.
alexk 9y ago
I can tell you what attracted me to Docker as an early adopter (while @Mailgun): * Very good user and developer experience. Docker felt like git for containers. Docker run, docker ps and other commands are awesome. * Very good and innovative build system. Dockerfiles are great and allow to build complex containers and efficiently package software in a convenient way. * Solving image distribution problems. Docker pull/push are great. * Layering system leading with build and run optimization. Overall docker not only provided a great UX, but combined all the patterns above in a very expressive system, great job done by the team.
brianm 9y ago
They have focused relentlessly on making it easy to use for every day development. Solaris Zones, BSD Jails, and LXC were around first, but were (relatively) arcane and finicky, and no one ever looked at bringing them to non-linux (or non-bsd for jails) dev laptops. OTOH, Docker made a good (enough) implementation, and went for developers, developers, developers. They brought it to Mac, to Windows, they engaged a wide audience and mostly listened. Focusing on day to day development for users came with tradeoffs -- ops oriented features came much later, getting serious about security came later, etc. These are all important things... but less so than ease of use and adoption. The pattern is not new, the same thing happened with Rails -- the concepts in rails were not novel, the extreme ease of getting started and getting to useful really fast was the killer feature (to get it going). After it got a big ecosystem, it got the quality aspect (mostly by replacing itself with merb). The lesson: if you want wide adoption, build something good and reduce every barrier to adoption you encounter. The most important features are the ones getting in way of people using it, not the ones people using it are having. You'll need to solve them, but solve adoption first.
- jitl 9y ago
  Astute. I was trying to use jails for development in kinda a proto-Docker setup, where my apps each ran in their own BSD jail. I struggled to put the pieces together to set up the jails, share a “base jail” with ZFS, forward ports, etc. I had scripts for messing with my pf rules to add port forwards, other scripts to update/apply config inside a jail... it was more frustrating to automate creating and destroying “immutable” jails, than maintaining a pet per app I developed... until I messed up an environment, and just abandoned the project! I think we’ll see the same sort of thing happening with FaaS frameworks, or any of the layers building on top of Swarm/Kubernetes/Mesos.
  - lilbobbytables 9y ago
    What do you mean, in reference to layers on kubernetes, mesos, etc?
  - inferiorhuman 9y ago
    Really? I've found iocage to work very well and combined with Ansible's jail support creating new jails is pretty darn easy. In terms of networking I created another loopback interface and assign each jail its own IP at creation time. It's not particularly elegant but it simplifies ipfw rules. I've automated doing some updates with jenkins+ansiblee+git, but overall maintaining them is a bit tough because ansible's pkgng support is lacking.
jdubs 9y ago
They nailed the developer experience which allowed so many people to build upon their interface.
dingo_bat 9y ago
I don't know of any other containerization technology except really small linux distros that you can run in virtual box. Maybe that's why dropbox is so popular. They marketed the hell out of it.
linkmotif 9y ago
Isn’t it simple? It was the first and only easy interface to LXC, which I think was the first and only Linux containerization framework, and Linux is the most popular server OS.
emmelaich 9y ago
It's not only a container tech, it's the container format and distribution.
latenite4 9y ago
Docker is popular because: 1. containers are technologically better than virtual machines 2. Docker has added a popular cloud container image repo which is used for accessing container images. 3. this Docker cloud repo has morphed into a popular platform for selling/distributing application software which is built into container images.
latenite4 9y ago
Docker is very popular because: 1. containers is technologically superior to virtual machines. 2. Docker has create a public cloud repo for sharing/selling container images. 3. The Docker cloud has become very popular way of distributing application software which is built into container images. Number 1 is technological reason, number 2,3 are non technical features which Docker added to containers and have become popular for enterprise software.
- ComputerGuru 9y ago
  Your premise is fatally objective and missing crucial nuance. There is by no means a consensus that Docker containers are “technologically superior” to virtual machines.. just lighter.
  - AstralStorm 9y ago
    Not even much lighter really. Compared to paravirt enhanced KVM at least. Maybe even Xen. Especially when you have cleancache and frontswap on. I would like to see actual facts for the alleged performance benefits. :)
    - ComputerGuru 9y ago
      Oh I very specifically said “lighter” and not faster, referencing only the distribution size. But not much lighter, even then. It just makes no sense to me to throw away an actual virtual machine for a mere abstraction of one.
alpb 9y ago
- It is the complete solution: the image format is easy to understand and well agreed upon, they also offer an image registry (they host it or you can host yourself) - Great UX: Docker Inc is probably one of the small companies that provide great developer experience. They have a natural skill for it. Another one would be HashiCorp tools. These companies understand developers well. When a tool naturally speak the same language as you, you fall in love with it. - They have a great development story: lxc, jails, zones, ... you can't get them to work on Windows or Mac. But Docker for [Mac|Windows] offers a complete development story (you don't have to be on Linux to develop Linux containers). - Solid image ecosystem: They paid external parties to keep the official images on Docker Hub (like mysql, nginx) solid i.e. up-to-date, free of critical security vulnerabilities. I don't know of any solid base-image ecosystems in other containerization ecosystems. - Big companies got behind it: This is a bit backwards, but since docker got popular, companies like Red Hat, IBM, Microsoft, Google started to contribute to it early on. This brought in a lot of mind share and publicity to project (and disagreements). - They got a solid PR machine: They do great community management. Docker Captains program is a solid one. They had many DockerCons they're all pretty good (although one would argue past few ones got kind of corporate/enterprise-y maybe even boring). But they had a few good ones. - The tech has merit: "docker run", "docker ps", "docker rm" the whole docker CLI is very intuitive overall. This is a bit of an supporting argument to UX, but it hides a lot of the details of how the docker-engine works.
- kavalg 9y ago
  Indeed, Docker was not perfect, but was easier to use than LXC at the time it got popular. There is a certain barrier in usability(cost) and usefulness(reward) that must be passed so that hype (natural or induced) can do the rest. Looking from a reward/cost perspective, this is how Docker appealed to me: Rewards: - Hygienic build&deployment - being able to specify your requirements down to the OS lib versions - Lower barrier to deployment (easy for users to try out my app and for me to try theirs) Costs (mostly time): - LXC was something that I understood, but could't make good use of to be worth it the time spent. Docker on the other hand required less time to do something useful (e.g. pull and run an image, turn an app to an image). Time to learn a new tech depends on its complexity (concepts and relationships) and how it is revealed to the user (docs, tutorials etc). Willingness to learn the complexity depends on the distribution of rewards along the time axis. I think Docker guys did a great job improving the latter. > But Docker for [Mac|Windows] offers a complete development story Docker on Windows has been a nightmare for me (crashes all the time) and I have abandoned altogether. I'd happily get rid of Windows too if it wasn't the required in my work environment.
justicezyx 9y ago
Docker is primarily a packaging framework + a runtime mechanism. It's like VM + hypervisor in one box. Thinking this way, it's easy to understand why it's popular. It did things that no other have done.
- djsumdog 9y ago
  It's not like that at all in any way. You're using existing OS packages in your base (apk in Alpine or apt in Debian/Ubuntu) to pull in all your dependencies and then placing your app on top of that. (Or using the base go, python or ruby container and letting it use pip/bundle to pull in dependencies and put your app on top of that). It only runs a single process, unlike a VM (or even an LXC container which is more similar to a VM). Containers are (mostly) immutable, so you're typically not running security updates on the same thing that provides all your dependencies. You should rebuild your containers when there are security updates .. but people rarely scan for those or do that; relying more on isolation and cgroups to keep those containerized apps safe. There's very little tooling within the container, so when things go wrong, you're either execing into a single container and apt-getting all the tools you need (which you gotta do each time you rebuild it) or you need to use something like sysdig. It's popular because you can create an easy to replicate artifact that doesn't rely on a ton of system dependencies with a really basic (although kinda primitive) package building system (Dockerfile) and that is way more lightweight than a VM while providing a pretty heavy layer of isolation.
  - bboreham 9y ago
    Small correction: Docker containers can run any number of processes. For example the standard apache container runs five.
    - jacques_chester 9y ago
      They can, but Docker-as-Docker won't support multiple processes. Instead you have to provide your own logic to spin up multiple processes.
  - justicezyx 9y ago
ComputerGuru 9y ago
Everyone keeps mentioning Windows support, but - and someone please correct me if I’m remembering wrong here - wasn’t it the new Microsoft with Nadella’s open source friendliness that went the extra mile to get Docker on Windows to happen?
- bboreham 9y ago
  "Docker for Windows" runs Linux containers in a Linux VM, with a thin Windows CLI and quite a nice install screen. It required no special help from Microsoft. The product that runs Docker containers natively is called "Windows Server 2016", and this required a vast amount of work from Microsoft. Native Windows containers are not seen much in the wild.
  - jacques_chester 9y ago
    > Native Windows containers are not seen much in the wild. Cloud Foundry has them for Windows 2012, though they're quite leaky. Windows 2016's support is much better and the resultant containers have much of what you want in terms of proper process isolation and dense utilisation. Disclosure: I work for Pivotal, we contribute to Cloud Foundry. The Windows container team sits two desks over from mine.
  - cube2222 9y ago
    Actually, they're on windows 10 too for some time already.
- jazoom 9y ago
  You may be right but it doesn't matter who did it. It's still possibly a factor in its success.
hvindin 9y ago
Just my cynical view, but I'm thinking it's because is got a friendly looking whale as a logo and the developers took the approach of making it friendly to use for someone who doesn't understand the underlying quite complex technology. I was involved in making the decision about introducing containers to my workplace, my original recommendation was to just go with chroots or buy into something that we could get vendor support for on RHEL6 (so not docker) and when asked to explain how this would benefit out desired outcome, the docker website basically had copy-pasteable words that did that job for me, chroots however just described he technical implementation of a chroot. So eventually I just went "fuck it, we'll run unsupported and take the risk, then well move N thousands of servers to RHEL7 because I don't want to have to explain to managers how cgroups and Linux kernel constructs work". About a year later most of the enterprise has a plan to move all their existing EL5/EL6 workloads to EL7 just in case they need to use docker some time in the future. Which, if I'm honest, I kind of regret, but it doesn't impact me that much so meh.
- user5994461 9y ago
  Which bank was it?
  - jayzalowitz 9y ago
    Some banks aren't doing this :p
21stio 9y ago
first mover advantage
zeta0134 9y ago
I strongly believe it's the ease of use factor. If you know nothing at all about containers, but have just installed docker, you can immediately "docker run httpd" and watch a web server install itself and do something useful in seconds. That's really powerful, and the surprisingly diverse selection of pre-built containers on the docket hub makes it even easier to bootstrap your project and figure the details out later. I don't have the necessary expertise to compare it meaningfully to other container systems so I can't speak to it's implementation details, but the first time user experience is more than enough to explain it's popularity.
dmitriid 9y ago
Despite what everyone is saying, Docker is not great UX, not easy to use etc. It has greater UX and it’s easier to use than the available alternatives.
- welly 9y ago
  Do you not think that if everyone is saying it has a great UX and it's easy to use then perhaps it does have a great UX and is easy to use?
  - dmitriid 9y ago
    We as developers are not spoilt for choice. The tools we use are universally crappy, horrible etc. Any improvement is hailed as great UX/DX even if the improvement is only marginal. Or if the improvement only touches on certain aspects and totally ignores all other aspects. Docker is an improvement over the cesspool of tools that existed in the space before it. It's UX is ok at best, and is hailed as awesome because it just barely covers the basic needs of a developer: list a thing, build a thing, remove a thing. Outside of really a handful of basic things it fails miserably and relies on multiple disparate hacks by desperate developers. The only reason it's being praised is that all other tools are so much worse.
    - dmitriid 9y ago
      Oh. Another thing that plays in Docker's favour: it does improve, albeit slowly and incrementally. Once again, it's only because everything else is worse + dev mindshare has been captured by Docker
    - imtringued 9y ago
      >The only reason it's being praised is that all other tools are so much worse. So you're saying docker is the best tool in this category?
      - dmitriid 9y ago
        It's a tool. Better than most others in some aspects. Also, "Best tool" !== "amazing UX" etc. etc.
mbrock 9y ago
I'm not even aware of any other container system that lets me run something like "docker run node" right now. So I vote for the infrastructure and hosted images which made it kind of like the GitHub of containers.
- oblio 9y ago
  https://linuxcontainers.org/lxc/manpages/man1/lxc-execute.1.html https://linuxcontainers.org/lxc/manpages/man1/lxc-execute.1.... -> lxc-execute is kind of similar to docker run, UI wise. But it's not the same thing as the Docker "package".
pbiggar 9y ago
I wrote something a few years ago about why docker matters: https://circleci.com/blog/it-really-is-the-future/ https://circleci.com/blog/it-really-is-the-future/ (excuse the slightly flippant tone). I think the answer to why it succeeded instead of the others is that it solved those problems (in particular the container format and the UX around it) much better than the alternatives.
fpoling 9y ago
For me the main reason to stick with docker is the fast build. Other solutions just do not have anything that usable to create images during development.
DyslexicAtheist 9y ago
the best part of docker isn't the containerization tech but the networking IMO.
reacharavindh 9y ago
This may be a good forum to ask. For an absolute newbie to Docker but someone who has used LxC a few times in non-serious situations, what would be a good learning resource? Just the docs? Any good book? Any blog post series?
- oblio 9y ago
  Read they're docs, they're quite good. Then just start using it. docker --help, look at the commands available, see what they do. It truly is quite intuitive and as you hit some barriers just google for answers, which you will find (yay, popularity!). Then create some Dockerfiles. After a few weeks you should know more than enough to use it to cover local development needs. If you want to go to prod with it then that can get quite tricky, depending on your scale. But, baby steps :)
fulafel 9y ago
The main reason is that the underlying Linux container tech has (especially in the past) such terrible usability. Try to use cgroups or other older tools for running your browser, for example.
zizek23 9y ago
Docker based on LXC and added a few things. The fact that they were well funded made outreach easier compared to the open source LXC project and Docker became many peoples first introduction to containers. Once they got traction they quickly dumped LXC around version 0.9 and created their own engine in GO. All the while misleading and letting misconceptions and plain untruths about LXC being 'difficult', some 'low level tool' or 'bash scripts' spread unchecked by their ecosystem. So the model is not only take open source tech, but bash them in public and forget about giving anything back. LXC is much simpler to use and understand both conceptually and in practical use. Docker is basically a hijack of an open source project supported by the SV crowd and the level of support and misinformation can be verified by HN posts in the last 3 years. Docker posts routinely clock 600-1000 votes in short periods of time and are full of marketing and misinformation. That's history but the culture continues. Docker and other related projects continue to liberally wrap open source projects while downplaying them, ie overlayfs, aufs, kernel namespaces, cgroups, Linux networking tools, nginx, consul, haproxy and more. Someone had to create those projects and make them usable. This would not be a bad thing if they actually made things simpler, but they keep adding more and more layers of complexity. What incentive is there for people to create these high value open source tools if vc funded companies like Docker and corporate funded projects like Kubernetes simply wrap them, downplay them and hog the attention and funding? These kind of projects basically cut the tree they sit on for their own short term benefit.
muzani 9y ago
I would say UX. Things like this need lots of people to adopt it to hit critical mass. UX lowers the friction level. It's more likely to be accepted by the simplest decision maker. This is why companies like Slack do so well.
lucaspottersky 9y ago
for me, because when i first heard about it my options were Chef/Puppet (with Vagrant)... so Docker was much, much simpler to get started. in the past years they've been adding a lot of complexity though... :meh:

144 points by justaj 9y ago

Has it only been the first mover effect or are there (decisive) features that other technologies don't have?

It depends on what you mean by Docker. As a container, it’s adds a lot of conveniences, despite that at the end of the day it all boils down to cgroups and namespaces. If you mean as a container orchestrator, I have no idea. Honestly Mesos seems much better than Docker or Kube in this regard. It scales better, is more reliable, and is more flexible. The one downside as I see it is there’s a steeper learning curve.

spoksmustache 9y ago

Because they spent two hundred million dollars promoting it.

jacques_chester 9y ago
They raised the money after, and largely because, it had popular groundswell amongst developers.

williamstein 9y ago

My guesses: Docker has been around a while, is mature and is battle tested; it was a bit ahead of other options when critical adoption decisions were being made. I remember using LXC in Debian (and Ubuntu) around 2013 and hitting a lot of disturbing bugs, due to immaturity...

user5994461 9y ago
It's not mature and not battle tested. There is barely anyone using it. They few who do are walking on eggs. it's hardly possible to find two experiments running the same ecosystem between all the distributions and the commercial services. Centos, Debian, RedHat, CoreOS, kubernetes, AWS ECS, Google container, cloud foundry, openshift...

minitech 9y ago

Can you list some alternatives you’d like to see it compared to?

justaj 9y ago
Sure: - LXC - Rkt - *BSD jails

gomangogo 9y ago

Because it is robust and lightweight. It tackled all the facets of apps isolation.

gaius 9y ago
It most certainly does not. If you are using Docker containers for security or QoS you're doing it wrong, and I think even Docker the company would concur. It's a fantastic packaging and deployment format, but it's not a universal solution.
- BrandoElFollito 9y ago
  Do you have any current sources for the security part? Everything I read is along the lines of "this is not secure, we think, but do not have any specific examples. But be careful"
  - gaius 9y ago
    https://news.ycombinator.com/item?id=16030107 https://news.ycombinator.com/item?id=16030107

directionless 9y ago

It's got a good name, and was an early mover in the field.

TheDong 9y ago
lxc and jails are both good names (in fact, I think bsd jails is the best name of those). lxc and jails both predate docker by quite a while.
- TheRealPomax 9y ago
  Jails is an absolutely terrible name when you need to sell your company, rather than your friends, on using this technology. "Pff, yeah right, no one rejects a technology just because the name has negative connotation in a different context", except that is literally what happens.
  - megaman22 9y ago
    Ah, the cockroachdb argument. We're rapidly approaching the point where any meaningful names are already in use, and everything uses nonsense names anyway.
    - TheRealPomax 9y ago
      Nonsense names are great, like "MySQL" or "Kubernetes". Names that the people you're trying to sell it to recognize from normal language like "jails", "cockroachdb", not so much. If you're in a startup and you need to sell it to your CTO: whatever. If you're in a 2k+ employee company and you need to sell it to general management: you are not going to be using jails, or cockroachdbs, or anything else that makes non-tech people raise their eyebrows in the bad way when they hear/read them.
      - stevesimmons 9y ago
        Kubernetes isn't a nonsense name. Κυβερνήτης is Ancient Greek for helmsman. Which is not unrelated to Docker.

maxaf 9y ago

What other containerization technologies?

peterkelly 9y ago
- chroot - Zones (Solaris) - Jails (FreeBSD) - OpenVZ (Linux) - LXC (Linux) - VServer (Linux) - lmctfy (Linux) - WPARs (AIX) ... and more; see https://en.wikipedia.org/wiki/Operating-system-level_virtualization https://en.wikipedia.org/wiki/Operating-system-level_virtual...
- djsumdog 9y ago
  Most people use LXC to run containers that run full operating systems right? (Where it loads init/systemd and then processes .. basically a full VM but lightweight?) The others are all more single process isolated, but how many others have the image building/hashing/layering system of Docker. I personally wish Docker was more of a first class citizen on FreeBSD, but the official port was way out of date the last time I checked.
- m1keil 9y ago
  I'm not sure about the rest but OpenVZ never got into mainline kernel and required custom extensions while Docker did not. It's probably very contributing factor.
- xorcist 9y ago
  Probably should add systemd-nspawn to that list. Regular systemd that you probably need to know how to use anyway can launch things in namespaces and even use common image formats. Very useful.
- drdaeman 9y ago
  Docker images is a simple quick-and-dirty packaging solution with all the pieces necessary (building, versioning, storage and deployment). I believe this is why it won. Don't think any of those other options had anything similar. The alternatives, like building and deploying apps with native OS packages (e.g. .debs) were significantly more complicated and less portable. (While it's not that Docker images are better than native packages, they're doubtlessly generally easier.)

westoque 9y ago

I came from using Vagrant at a previous company and from my experience, Docker is just more lightweight, portable, and user friendly. Share a file/folder? Expose a port? Get an image and run a container? You can do it easily using Docker cli. You want a UI tool that makes that task even easier for you, get Kitematic. Also, Docker just has more development and maturity at this stage that it makes deployments easier.

alexk 9y ago

I can tell you what attracted me to Docker as an early adopter (while @Mailgun): * Very good user and developer experience. Docker felt like git for containers. Docker run, docker ps and other commands are awesome. * Very good and innovative build system. Dockerfiles are great and allow to build complex containers and efficiently package software in a convenient way. * Solving image distribution problems. Docker pull/push are great. * Layering system leading with build and run optimization. Overall docker not only provided a great UX, but combined all the patterns above in a very expressive system, great job done by the team.

brianm 9y ago

They have focused relentlessly on making it easy to use for every day development. Solaris Zones, BSD Jails, and LXC were around first, but were (relatively) arcane and finicky, and no one ever looked at bringing them to non-linux (or non-bsd for jails) dev laptops. OTOH, Docker made a good (enough) implementation, and went for developers, developers, developers. They brought it to Mac, to Windows, they engaged a wide audience and mostly listened. Focusing on day to day development for users came with tradeoffs -- ops oriented features came much later, getting serious about security came later, etc. These are all important things... but less so than ease of use and adoption. The pattern is not new, the same thing happened with Rails -- the concepts in rails were not novel, the extreme ease of getting started and getting to useful really fast was the killer feature (to get it going). After it got a big ecosystem, it got the quality aspect (mostly by replacing itself with merb). The lesson: if you want wide adoption, build something good and reduce every barrier to adoption you encounter. The most important features are the ones getting in way of people using it, not the ones people using it are having. You'll need to solve them, but solve adoption first.

jitl 9y ago
Astute. I was trying to use jails for development in kinda a proto-Docker setup, where my apps each ran in their own BSD jail. I struggled to put the pieces together to set up the jails, share a “base jail” with ZFS, forward ports, etc. I had scripts for messing with my pf rules to add port forwards, other scripts to update/apply config inside a jail... it was more frustrating to automate creating and destroying “immutable” jails, than maintaining a pet per app I developed... until I messed up an environment, and just abandoned the project! I think we’ll see the same sort of thing happening with FaaS frameworks, or any of the layers building on top of Swarm/Kubernetes/Mesos.
- lilbobbytables 9y ago
  What do you mean, in reference to layers on kubernetes, mesos, etc?
- inferiorhuman 9y ago
  Really? I've found iocage to work very well and combined with Ansible's jail support creating new jails is pretty darn easy. In terms of networking I created another loopback interface and assign each jail its own IP at creation time. It's not particularly elegant but it simplifies ipfw rules. I've automated doing some updates with jenkins+ansiblee+git, but overall maintaining them is a bit tough because ansible's pkgng support is lacking.

jdubs 9y ago

They nailed the developer experience which allowed so many people to build upon their interface.

dingo_bat 9y ago

I don't know of any other containerization technology except really small linux distros that you can run in virtual box. Maybe that's why dropbox is so popular. They marketed the hell out of it.

linkmotif 9y ago

Isn’t it simple? It was the first and only easy interface to LXC, which I think was the first and only Linux containerization framework, and Linux is the most popular server OS.

emmelaich 9y ago

It's not only a container tech, it's the container format and distribution.

latenite4 9y ago

Docker is popular because: 1. containers are technologically better than virtual machines 2. Docker has added a popular cloud container image repo which is used for accessing container images. 3. this Docker cloud repo has morphed into a popular platform for selling/distributing application software which is built into container images.

latenite4 9y ago

Docker is very popular because: 1. containers is technologically superior to virtual machines. 2. Docker has create a public cloud repo for sharing/selling container images. 3. The Docker cloud has become very popular way of distributing application software which is built into container images. Number 1 is technological reason, number 2,3 are non technical features which Docker added to containers and have become popular for enterprise software.

ComputerGuru 9y ago
Your premise is fatally objective and missing crucial nuance. There is by no means a consensus that Docker containers are “technologically superior” to virtual machines.. just lighter.
- AstralStorm 9y ago
  Not even much lighter really. Compared to paravirt enhanced KVM at least. Maybe even Xen. Especially when you have cleancache and frontswap on. I would like to see actual facts for the alleged performance benefits. :)
  - ComputerGuru 9y ago
    Oh I very specifically said “lighter” and not faster, referencing only the distribution size. But not much lighter, even then. It just makes no sense to me to throw away an actual virtual machine for a mere abstraction of one.

alpb 9y ago

- It is the complete solution: the image format is easy to understand and well agreed upon, they also offer an image registry (they host it or you can host yourself) - Great UX: Docker Inc is probably one of the small companies that provide great developer experience. They have a natural skill for it. Another one would be HashiCorp tools. These companies understand developers well. When a tool naturally speak the same language as you, you fall in love with it. - They have a great development story: lxc, jails, zones, ... you can't get them to work on Windows or Mac. But Docker for [Mac|Windows] offers a complete development story (you don't have to be on Linux to develop Linux containers). - Solid image ecosystem: They paid external parties to keep the official images on Docker Hub (like mysql, nginx) solid i.e. up-to-date, free of critical security vulnerabilities. I don't know of any solid base-image ecosystems in other containerization ecosystems. - Big companies got behind it: This is a bit backwards, but since docker got popular, companies like Red Hat, IBM, Microsoft, Google started to contribute to it early on. This brought in a lot of mind share and publicity to project (and disagreements). - They got a solid PR machine: They do great community management. Docker Captains program is a solid one. They had many DockerCons they're all pretty good (although one would argue past few ones got kind of corporate/enterprise-y maybe even boring). But they had a few good ones. - The tech has merit: "docker run", "docker ps", "docker rm" the whole docker CLI is very intuitive overall. This is a bit of an supporting argument to UX, but it hides a lot of the details of how the docker-engine works.

kavalg 9y ago
Indeed, Docker was not perfect, but was easier to use than LXC at the time it got popular. There is a certain barrier in usability(cost) and usefulness(reward) that must be passed so that hype (natural or induced) can do the rest. Looking from a reward/cost perspective, this is how Docker appealed to me: Rewards: - Hygienic build&deployment - being able to specify your requirements down to the OS lib versions - Lower barrier to deployment (easy for users to try out my app and for me to try theirs) Costs (mostly time): - LXC was something that I understood, but could't make good use of to be worth it the time spent. Docker on the other hand required less time to do something useful (e.g. pull and run an image, turn an app to an image). Time to learn a new tech depends on its complexity (concepts and relationships) and how it is revealed to the user (docs, tutorials etc). Willingness to learn the complexity depends on the distribution of rewards along the time axis. I think Docker guys did a great job improving the latter. > But Docker for [Mac|Windows] offers a complete development story Docker on Windows has been a nightmare for me (crashes all the time) and I have abandoned altogether. I'd happily get rid of Windows too if it wasn't the required in my work environment.

justicezyx 9y ago

Docker is primarily a packaging framework + a runtime mechanism. It's like VM + hypervisor in one box. Thinking this way, it's easy to understand why it's popular. It did things that no other have done.

djsumdog 9y ago
It's not like that at all in any way. You're using existing OS packages in your base (apk in Alpine or apt in Debian/Ubuntu) to pull in all your dependencies and then placing your app on top of that. (Or using the base go, python or ruby container and letting it use pip/bundle to pull in dependencies and put your app on top of that). It only runs a single process, unlike a VM (or even an LXC container which is more similar to a VM). Containers are (mostly) immutable, so you're typically not running security updates on the same thing that provides all your dependencies. You should rebuild your containers when there are security updates .. but people rarely scan for those or do that; relying more on isolation and cgroups to keep those containerized apps safe. There's very little tooling within the container, so when things go wrong, you're either execing into a single container and apt-getting all the tools you need (which you gotta do each time you rebuild it) or you need to use something like sysdig. It's popular because you can create an easy to replicate artifact that doesn't rely on a ton of system dependencies with a really basic (although kinda primitive) package building system (Dockerfile) and that is way more lightweight than a VM while providing a pretty heavy layer of isolation.
- bboreham 9y ago
  Small correction: Docker containers can run any number of processes. For example the standard apache container runs five.
  - jacques_chester 9y ago
    They can, but Docker-as-Docker won't support multiple processes. Instead you have to provide your own logic to spin up multiple processes.
- justicezyx 9y ago

ComputerGuru 9y ago

Everyone keeps mentioning Windows support, but - and someone please correct me if I’m remembering wrong here - wasn’t it the new Microsoft with Nadella’s open source friendliness that went the extra mile to get Docker on Windows to happen?

bboreham 9y ago
"Docker for Windows" runs Linux containers in a Linux VM, with a thin Windows CLI and quite a nice install screen. It required no special help from Microsoft. The product that runs Docker containers natively is called "Windows Server 2016", and this required a vast amount of work from Microsoft. Native Windows containers are not seen much in the wild.
- jacques_chester 9y ago
  > Native Windows containers are not seen much in the wild. Cloud Foundry has them for Windows 2012, though they're quite leaky. Windows 2016's support is much better and the resultant containers have much of what you want in terms of proper process isolation and dense utilisation. Disclosure: I work for Pivotal, we contribute to Cloud Foundry. The Windows container team sits two desks over from mine.
- cube2222 9y ago
  Actually, they're on windows 10 too for some time already.
jazoom 9y ago
You may be right but it doesn't matter who did it. It's still possibly a factor in its success.

hvindin 9y ago

Just my cynical view, but I'm thinking it's because is got a friendly looking whale as a logo and the developers took the approach of making it friendly to use for someone who doesn't understand the underlying quite complex technology. I was involved in making the decision about introducing containers to my workplace, my original recommendation was to just go with chroots or buy into something that we could get vendor support for on RHEL6 (so not docker) and when asked to explain how this would benefit out desired outcome, the docker website basically had copy-pasteable words that did that job for me, chroots however just described he technical implementation of a chroot. So eventually I just went "fuck it, we'll run unsupported and take the risk, then well move N thousands of servers to RHEL7 because I don't want to have to explain to managers how cgroups and Linux kernel constructs work". About a year later most of the enterprise has a plan to move all their existing EL5/EL6 workloads to EL7 just in case they need to use docker some time in the future. Which, if I'm honest, I kind of regret, but it doesn't impact me that much so meh.

user5994461 9y ago
Which bank was it?
- jayzalowitz 9y ago
  Some banks aren't doing this :p

21stio 9y ago

first mover advantage

zeta0134 9y ago

I strongly believe it's the ease of use factor. If you know nothing at all about containers, but have just installed docker, you can immediately "docker run httpd" and watch a web server install itself and do something useful in seconds. That's really powerful, and the surprisingly diverse selection of pre-built containers on the docket hub makes it even easier to bootstrap your project and figure the details out later. I don't have the necessary expertise to compare it meaningfully to other container systems so I can't speak to it's implementation details, but the first time user experience is more than enough to explain it's popularity.

dmitriid 9y ago

Despite what everyone is saying, Docker is not great UX, not easy to use etc. It has greater UX and it’s easier to use than the available alternatives.

welly 9y ago
Do you not think that if everyone is saying it has a great UX and it's easy to use then perhaps it does have a great UX and is easy to use?
- dmitriid 9y ago
  We as developers are not spoilt for choice. The tools we use are universally crappy, horrible etc. Any improvement is hailed as great UX/DX even if the improvement is only marginal. Or if the improvement only touches on certain aspects and totally ignores all other aspects. Docker is an improvement over the cesspool of tools that existed in the space before it. It's UX is ok at best, and is hailed as awesome because it just barely covers the basic needs of a developer: list a thing, build a thing, remove a thing. Outside of really a handful of basic things it fails miserably and relies on multiple disparate hacks by desperate developers. The only reason it's being praised is that all other tools are so much worse.
  - dmitriid 9y ago
    Oh. Another thing that plays in Docker's favour: it does improve, albeit slowly and incrementally. Once again, it's only because everything else is worse + dev mindshare has been captured by Docker
  - imtringued 9y ago
    >The only reason it's being praised is that all other tools are so much worse. So you're saying docker is the best tool in this category?
    - dmitriid 9y ago
      It's a tool. Better than most others in some aspects. Also, "Best tool" !== "amazing UX" etc. etc.

mbrock 9y ago

I'm not even aware of any other container system that lets me run something like "docker run node" right now. So I vote for the infrastructure and hosted images which made it kind of like the GitHub of containers.

oblio 9y ago
https://linuxcontainers.org/lxc/manpages/man1/lxc-execute.1.html https://linuxcontainers.org/lxc/manpages/man1/lxc-execute.1.... -> lxc-execute is kind of similar to docker run, UI wise. But it's not the same thing as the Docker "package".

pbiggar 9y ago

I wrote something a few years ago about why docker matters: https://circleci.com/blog/it-really-is-the-future/ https://circleci.com/blog/it-really-is-the-future/ (excuse the slightly flippant tone). I think the answer to why it succeeded instead of the others is that it solved those problems (in particular the container format and the UX around it) much better than the alternatives.

fpoling 9y ago

For me the main reason to stick with docker is the fast build. Other solutions just do not have anything that usable to create images during development.

DyslexicAtheist 9y ago

the best part of docker isn't the containerization tech but the networking IMO.

reacharavindh 9y ago

This may be a good forum to ask. For an absolute newbie to Docker but someone who has used LxC a few times in non-serious situations, what would be a good learning resource? Just the docs? Any good book? Any blog post series?

oblio 9y ago
Read they're docs, they're quite good. Then just start using it. docker --help, look at the commands available, see what they do. It truly is quite intuitive and as you hit some barriers just google for answers, which you will find (yay, popularity!). Then create some Dockerfiles. After a few weeks you should know more than enough to use it to cover local development needs. If you want to go to prod with it then that can get quite tricky, depending on your scale. But, baby steps :)

fulafel 9y ago

The main reason is that the underlying Linux container tech has (especially in the past) such terrible usability. Try to use cgroups or other older tools for running your browser, for example.

zizek23 9y ago

Docker based on LXC and added a few things. The fact that they were well funded made outreach easier compared to the open source LXC project and Docker became many peoples first introduction to containers. Once they got traction they quickly dumped LXC around version 0.9 and created their own engine in GO. All the while misleading and letting misconceptions and plain untruths about LXC being 'difficult', some 'low level tool' or 'bash scripts' spread unchecked by their ecosystem. So the model is not only take open source tech, but bash them in public and forget about giving anything back. LXC is much simpler to use and understand both conceptually and in practical use. Docker is basically a hijack of an open source project supported by the SV crowd and the level of support and misinformation can be verified by HN posts in the last 3 years. Docker posts routinely clock 600-1000 votes in short periods of time and are full of marketing and misinformation. That's history but the culture continues. Docker and other related projects continue to liberally wrap open source projects while downplaying them, ie overlayfs, aufs, kernel namespaces, cgroups, Linux networking tools, nginx, consul, haproxy and more. Someone had to create those projects and make them usable. This would not be a bad thing if they actually made things simpler, but they keep adding more and more layers of complexity. What incentive is there for people to create these high value open source tools if vc funded companies like Docker and corporate funded projects like Kubernetes simply wrap them, downplay them and hog the attention and funding? These kind of projects basically cut the tree they sit on for their own short term benefit.

muzani 9y ago

I would say UX. Things like this need lots of people to adopt it to hit critical mass. UX lowers the friction level. It's more likely to be accepted by the simplest decision maker. This is why companies like Slack do so well.

lucaspottersky 9y ago

for me, because when i first heard about it my options were Chef/Puppet (with Vagrant)... so Docker was much, much simpler to get started. in the past years they've been adding a lot of complexity though... :meh: