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Ask HN: What is the actual purpose of Docker?

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Re: Ask HN: What is the actual purpose of Docker?

#81

Post by jdoss »

justincormack wrote: post #74
jdoss wrote: post #37

Earlier quoted context omitted.

> Docker has much wider adoption than OpenVZ does now. I don't think your statement is true at this point in time. OpenVZ is used by a ton of companies in the hosting industry and by large companies such as Groupon and smaller ones like TravisCI [1]. I would't make a statement that that Docker has a wider adoption than OpenVZ at this point in time. Maybe in five years, yes it may have a wider adoption than OpenVZ. Op…

Travis moved to Docker after that [1]. And the "hosting industry" is not the thing it used to be since cloud. [1] http://blog.travis-ci.com/2014-12-17-faster-builds-with-cont...

Very cool on the Docker move by Travis. I still think Docker has a long way to go to over take OpenVZ. Docker is gaining steam, but it's adoption rate isn't wider than OpenVZ. Not yet.

I agree that the hosting industry isn't what it used to be. Most of the larger hosting providers are not keeping up with the current trends and deployment methods, but that is mostly due to the fact that they do not need change. Most people who are buying commodity hosting don't have a team of developers and operations guys to use all the new cool cloud methods like Docker.

Re: Ask HN: What is the actual purpose of Docker?

#82

Post by yebyen »

javajosh wrote: post #73
shawnee_ wrote: post #71

Docker is a cute little tool that gives people who aren't that great at Linux the illusion that they know what they're doing. Throw in the use of some "Container" semantics and people become convinced it's that easy (and secure) to abstract away the containers from the kernel. But it's not, at least in my experience; not to mention that as of now, anything running Docker in production (probably a bad idea) is wide op…

>Docker is a cute little tool that gives people who aren't that great at Linux the illusion that they know what they're doing. Well, that's what I personally hoped . Then you run into problems, distro specific problems, and find yourself unable to deal with it without actually becoming great at linux under a deadline. Docker can actually introduce tremendous complexity at both the Linux and application level because…

I'm sure this is not the answer you are looking for, but you can 'docker export' a container to a tar file and examine your image file that way.

(1) You're exporting a container, not an image, so if you wanted to export your image, deploy it to a container first. Run echo or some other noop if you need to.

(2) This is similar to how git operates. You wouldn't want to examine your git commits interactively (assuming that means the ability to change them in place) well, if you did, git has --amend, but no such thing exists in Docker.

An image with a given id is supposed to be permanent and unchanging, containers change and can be re-committed, but images don't change. They just have children.

It can get hairy when you reach the image layer limit, because using up the last allowed image layer means you can't deploy to a container anymore. So, how do you export the image? 'docker save' -- but 'docker save' exports the image and all of its parent layers separately. (you need to flatten it, for example?)

I once wrote this horrible script[1] whose only purpose was unrolling this mess, since the latest image had the important state that I wanted in it, but I needed the whole image -- so, untar them all in reverse order and then you have the latest everything in a single directory that represents your image filesystem.

The horror of this script leads me to believe this is an oversight as well, but a wise docker guru probably once said "your first mistake was keeping any state in your container at all."

[1]: https://raw.githubusercontent.com/yebyen/urbinit/del/doit.sh

Re: Ask HN: What is the actual purpose of Docker?

#83

Post by dasil003 »

shawnee_ wrote: post #71

Docker is a cute little tool that gives people who aren't that great at Linux the illusion that they know what they're doing. Throw in the use of some "Container" semantics and people become convinced it's that easy (and secure) to abstract away the containers from the kernel. But it's not, at least in my experience; not to mention that as of now, anything running Docker in production (probably a bad idea) is wide op…

> Docker is a cute little tool that gives people who aren't that great at Linux the illusion that they know what they're doing.

That's a rather embittered perspective, ironic considering how new Linux is in the grand scheme of things. A more germane perspective is that Docker is a new tool which acknowledges that UX matters even for system tools.

Re: Ask HN: What is the actual purpose of Docker?

#84

Post by zwischenzug »

arenaninja wrote: post #80
zwischenzug wrote: post #33

Some key points: - Docker is nothing new - it's a packaging of pre-existing technologies (cgroups, namespaces, AUFS) into a single place - Docker has traction, ecosystem, community and support from big vendors - Docker is _very_ fast and lightweight compared to VMs in terms of provisioning, memory usage, cpu usage and disk space - Docker abstracts applications, not machines, which is good enough for many purposes Som…

Docker is indeed fast and lightweight. It's amazing how much CPU power is freed up from not running a full on VM in VirtualBox. That said, I'm wary of running it in production

Why? Security?

Re: Ask HN: What is the actual purpose of Docker?

#85

Post by jessaustin »

crdoconnor wrote: post #53
grhmc wrote: post #38

Earlier quoted context omitted.

> How is building a Vagrant box via Ansible configuration any different than building a Docker container with a docker file? Unless you're snapshotting that vagrant box and then deploying that to all your servers somehow, you are building multiple times. > What is this rule to only build once? I'd recommend reading the book Continuous Delivery. It is a fantastically helpful read. I prefer not to update my machines, b…

>Unless you're snapshotting that vagrant box and then deploying that to all your servers somehow, you are building multiple times. You're also configuring many things in many different potentially complex ways. The docker method of using environment variables as a configuration hack to get around this is pretty horrible, IMHO. Especially compared to ansible's YAML/jinja2 configuration.

Some smart people disagree with that:

http://12factor.net/config

I think the point is not to conflate configuration that is equivalent to code (which, sure, put it in version control) with configuration that is specific to how code is deployed (which your deployment tool should just tell you, via env vars).

Re: Ask HN: What is the actual purpose of Docker?

#86

Post by juliangregorian »

shawnee_ wrote: post #71

Docker is a cute little tool that gives people who aren't that great at Linux the illusion that they know what they're doing. Throw in the use of some "Container" semantics and people become convinced it's that easy (and secure) to abstract away the containers from the kernel. But it's not, at least in my experience; not to mention that as of now, anything running Docker in production (probably a bad idea) is wide op…

Fine, I'll bite: what non-cute tool do big boys who are "great at Linux" and do know what they're doing use?

Re: Ask HN: What is the actual purpose of Docker?

#87

Post by arenaninja »

zwischenzug wrote: post #84
arenaninja wrote: post #80

Earlier quoted context omitted.

Docker is indeed fast and lightweight. It's amazing how much CPU power is freed up from not running a full on VM in VirtualBox. That said, I'm wary of running it in production

Why? Security?

Yep. I don't understand the security implications well enough to guard against them. As much as I like cutting edge tech I prefer to not actually cut myself with it!

Re: Ask HN: What is the actual purpose of Docker?

#88

Post by juliangregorian »

rahimnathwani wrote: post #54
ageofwant wrote: post #20

Earlier quoted context omitted.

> docker and openVZ aim to do the same thing. docker is a process container not a system container. > docker is a glorified chroot and cgroup wrapper. that is fairly immaterial, suffice to say that the underlying linux core tech that enables docker has matured enough lately to enable a tool like docker. I built many containers and I never thought about them in terms of the underlying tech. > There is also a library o…

"Assemble a system out of several containers, don't mash it all up into one - most people don't seem to get this about docker." Care to elaborate on this? Do you use the linking system described here? https://docs.docker.com/userguide/dockerlinks/ I mean, your various containers still communicate over IP, right? Just a private IP network within the host, rather than outside? (Obviously I've never used Docker.)

Yes, except each container has it's own isolated network and explicitly exposes a port that linked containers can listen to. In development I think a lot of people just use --net=host so that all the containers share the host networking stack (at least, I do).

Re: Ask HN: What is the actual purpose of Docker?

#89

Post by hosh »

You're coming at this from the wrong direction, namely virtualization.

What differentiates Docker is not virtualization, so much as package management. Docker is a package management tool that happens to allow you to execute the content of the package with some sort of isolation.

Further, when you look at it from that angle, you start seeing the flaws with it, as well as it's potential. It's no accident that Rocket and the Open Container Project are arising to standardize the container format. Other, less-well-known efforts include being able to distribute the container format themselves in a p2p distribution system, such as IPFS.

Re: Ask HN: What is the actual purpose of Docker?

#90

Post by hosh »

KaiserPro wrote: post #51
ageofwant wrote: post #20

Earlier quoted context omitted.

> docker and openVZ aim to do the same thing. docker is a process container not a system container. > docker is a glorified chroot and cgroup wrapper. that is fairly immaterial, suffice to say that the underlying linux core tech that enables docker has matured enough lately to enable a tool like docker. I built many containers and I never thought about them in terms of the underlying tech. > There is also a library o…

edit this sounds like I'm being petty, I apologise, I'm just typing fast. > docker is a process container not a system container. Valid. However the difference between docker image and openVZ images is the inclusion of an init system. > Have to disagree here, primarily because each service should live in each own container, docker is a process container, not a system container. Assemble a system out of several contai…

> However the difference between docker image and openVZ images is the inclusion of an init system.

No it isn't. Most people don't use an init system with Docker images. However, one of the top-10 popular images uses one -- the Passenger Phusion base images. They make a pretty compelling argument why you should.

None of these arguments are relevant in the big picture. Where Docker shines is the package management, not the virtualization. As a package management system, it is brilliant -- though incomplete. The package management could be fully content-addressable, and at which point, we'll have something more brilliant than what it is now. But it isn't, and I doubt anyone will try it until after this core concept gets adopted into the mainstream.

Ten years ago in 2005, I've heard these same types of arguments about cloud providers, the Zen hypervisors, and the AWS API. I've seen old mainframe folks rolling their eyes saying the technology is old, and this is hyped up. Of course it's hyped up; but unless you can look past the hype and your contempt, you won't see what's really there. No one is really arguing about cloud technology now, and the hold-outs are outnumbered by the majority.

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