mirror of
https://github.com/moby/moby.git
synced 2022-11-09 12:21:53 -05:00
b187d7ae41
Docker-DCO-1.1-Signed-off-by: James Turnbull <james@lovedthanlost.net> (github: jamtur01)
224 lines
9.4 KiB
ReStructuredText
224 lines
9.4 KiB
ReStructuredText
:title: FAQ
|
|
:description: Most frequently asked questions.
|
|
:keywords: faq, questions, documentation, docker
|
|
|
|
FAQ
|
|
===
|
|
|
|
|
|
Most frequently asked questions.
|
|
--------------------------------
|
|
|
|
How much does Docker cost?
|
|
..........................
|
|
|
|
Docker is 100% free, it is open source, so you can use it without paying.
|
|
|
|
What open source license are you using?
|
|
.......................................
|
|
|
|
We are using the Apache License Version 2.0, see it here:
|
|
https://github.com/dotcloud/docker/blob/master/LICENSE
|
|
|
|
Does Docker run on Mac OS X or Windows?
|
|
.......................................
|
|
|
|
Not at this time, Docker currently only runs on Linux, but you can
|
|
use VirtualBox to run Docker in a virtual machine on your box, and
|
|
get the best of both worlds. Check out the :ref:`macosx` and
|
|
:ref:`windows` installation guides. The small Linux distribution boot2docker
|
|
can be run inside virtual machines on these two operating systems.
|
|
|
|
How do containers compare to virtual machines?
|
|
..............................................
|
|
|
|
They are complementary. VMs are best used to allocate chunks of
|
|
hardware resources. Containers operate at the process level, which
|
|
makes them very lightweight and perfect as a unit of software
|
|
delivery.
|
|
|
|
What does Docker add to just plain LXC?
|
|
.......................................
|
|
|
|
Docker is not a replacement for LXC. "LXC" refers to capabilities
|
|
of the Linux kernel (specifically namespaces and control groups)
|
|
which allow sandboxing processes from one another, and controlling
|
|
their resource allocations. On top of this low-level foundation of
|
|
kernel features, Docker offers a high-level tool with several
|
|
powerful functionalities:
|
|
|
|
* *Portable deployment across machines.*
|
|
Docker defines a format for bundling an application and all its
|
|
dependencies into a single object which can be transferred to
|
|
any Docker-enabled machine, and executed there with the
|
|
guarantee that the execution environment exposed to the
|
|
application will be the same. LXC implements process sandboxing,
|
|
which is an important pre-requisite for portable deployment, but
|
|
that alone is not enough for portable deployment. If you sent me
|
|
a copy of your application installed in a custom LXC
|
|
configuration, it would almost certainly not run on my machine
|
|
the way it does on yours, because it is tied to your machine's
|
|
specific configuration: networking, storage, logging, distro,
|
|
etc. Docker defines an abstraction for these machine-specific
|
|
settings, so that the exact same Docker container can run -
|
|
unchanged - on many different machines, with many different
|
|
configurations.
|
|
|
|
* *Application-centric.*
|
|
Docker is optimized for the deployment of applications, as
|
|
opposed to machines. This is reflected in its API, user
|
|
interface, design philosophy and documentation. By contrast, the
|
|
``lxc`` helper scripts focus on containers as lightweight
|
|
machines - basically servers that boot faster and need less
|
|
RAM. We think there's more to containers than just that.
|
|
|
|
* *Automatic build.*
|
|
Docker includes :ref:`a tool for developers to automatically
|
|
assemble a container from their source code <dockerbuilder>`,
|
|
with full control over application dependencies, build tools,
|
|
packaging etc. They are free to use ``make, maven, chef, puppet,
|
|
salt,`` Debian packages, RPMs, source tarballs, or any
|
|
combination of the above, regardless of the configuration of the
|
|
machines.
|
|
|
|
* *Versioning.*
|
|
Docker includes git-like capabilities for tracking successive
|
|
versions of a container, inspecting the diff between versions,
|
|
committing new versions, rolling back etc. The history also
|
|
includes how a container was assembled and by whom, so you get
|
|
full traceability from the production server all the way back to
|
|
the upstream developer. Docker also implements incremental
|
|
uploads and downloads, similar to ``git pull``, so new versions
|
|
of a container can be transferred by only sending diffs.
|
|
|
|
* *Component re-use.*
|
|
Any container can be used as a :ref:`"base image"
|
|
<base_image_def>` to create more specialized components. This
|
|
can be done manually or as part of an automated build. For
|
|
example you can prepare the ideal Python environment, and use it
|
|
as a base for 10 different applications. Your ideal Postgresql
|
|
setup can be re-used for all your future projects. And so on.
|
|
|
|
* *Sharing.*
|
|
Docker has access to a `public registry
|
|
<http://index.docker.io>`_ where thousands of people have
|
|
uploaded useful containers: anything from Redis, CouchDB,
|
|
Postgres to IRC bouncers to Rails app servers to Hadoop to base
|
|
images for various Linux distros. The :ref:`registry
|
|
<registryindexspec>` also includes an official "standard
|
|
library" of useful containers maintained by the Docker team. The
|
|
registry itself is open-source, so anyone can deploy their own
|
|
registry to store and transfer private containers, for internal
|
|
server deployments for example.
|
|
|
|
* *Tool ecosystem.*
|
|
Docker defines an API for automating and customizing the
|
|
creation and deployment of containers. There are a huge number
|
|
of tools integrating with Docker to extend its
|
|
capabilities. PaaS-like deployment (Dokku, Deis, Flynn),
|
|
multi-node orchestration (Maestro, Salt, Mesos, Openstack Nova),
|
|
management dashboards (docker-ui, Openstack Horizon, Shipyard),
|
|
configuration management (Chef, Puppet), continuous integration
|
|
(Jenkins, Strider, Travis), etc. Docker is rapidly establishing
|
|
itself as the standard for container-based tooling.
|
|
|
|
What is different between a Docker container and a VM?
|
|
......................................................
|
|
|
|
There's a great StackOverflow answer `showing the differences <http://stackoverflow.com/questions/16047306/how-is-docker-io-different-from-a-normal-virtual-machine>`_.
|
|
|
|
Do I lose my data when the container exits?
|
|
...........................................
|
|
|
|
Not at all! Any data that your application writes to disk gets preserved
|
|
in its container until you explicitly delete the container. The file
|
|
system for the container persists even after the container halts.
|
|
|
|
How far do Docker containers scale?
|
|
...................................
|
|
|
|
Some of the largest server farms in the world today are based on containers.
|
|
Large web deployments like Google and Twitter, and platform providers such as
|
|
Heroku and dotCloud all run on container technology, at a scale of hundreds of
|
|
thousands or even millions of containers running in parallel.
|
|
|
|
How do I connect Docker containers?
|
|
...................................
|
|
|
|
Currently the recommended way to link containers is via the `link` primitive.
|
|
You can see details of how to `work with links here
|
|
<http://docs.docker.io/en/latest/use/working_with_links_names/>`_.
|
|
|
|
Also of useful when enabling more flexible service portability is the
|
|
`Ambassador linking pattern
|
|
<http://docs.docker.io/en/latest/use/ambassador_pattern_linking/>`_.
|
|
|
|
How do I run more than one process in a Docker container?
|
|
.........................................................
|
|
|
|
Any capable process supervisor such as http://supervisord.org/, runit, s6, or
|
|
daemontools can do the trick. Docker will start up the process management
|
|
daemon which will then fork to run additional processes. As long as the
|
|
processor manager daemon continues to run, the container will continue to as
|
|
well. You can see a more substantial example `that uses supervisord here
|
|
<http://docs.docker.io/en/latest/examples/using_supervisord/>`_.
|
|
|
|
What platforms does Docker run on?
|
|
..................................
|
|
|
|
Linux:
|
|
|
|
- Ubuntu 12.04, 13.04 et al
|
|
- Fedora 19/20+
|
|
- RHEL 6.5+
|
|
- Centos 6+
|
|
- Gentoo
|
|
- ArchLinux
|
|
- openSUSE 12.3+
|
|
- CRUX 3.0+
|
|
|
|
Cloud:
|
|
|
|
- Amazon EC2
|
|
- Google Compute Engine
|
|
- Rackspace
|
|
|
|
How do I report a security issue with Docker?
|
|
.............................................
|
|
|
|
You can learn about the project's security policy `here <http://www.docker.io/security/>`_
|
|
and report security issues to this `mailbox <mailto:security@docker.com>`_.
|
|
|
|
Why do I need to sign my commits to Docker with the DCO?
|
|
........................................................
|
|
|
|
Please read `our blog post <http://blog.docker.io/2014/01/docker-code-contributions-require-developer-certificate-of-origin/>`_ on the introduction of the DCO.
|
|
|
|
Can I help by adding some questions and answers?
|
|
................................................
|
|
|
|
Definitely! You can fork `the repo`_ and edit the documentation sources.
|
|
|
|
|
|
Where can I find more answers?
|
|
..............................
|
|
|
|
You can find more answers on:
|
|
|
|
* `Docker user mailinglist`_
|
|
* `Docker developer mailinglist`_
|
|
* `IRC, docker on freenode`_
|
|
* `GitHub`_
|
|
* `Ask questions on Stackoverflow`_
|
|
* `Join the conversation on Twitter`_
|
|
|
|
|
|
.. _Docker user mailinglist: https://groups.google.com/d/forum/docker-user
|
|
.. _Docker developer mailinglist: https://groups.google.com/d/forum/docker-dev
|
|
.. _the repo: http://www.github.com/dotcloud/docker
|
|
.. _IRC, docker on freenode: irc://chat.freenode.net#docker
|
|
.. _Github: http://www.github.com/dotcloud/docker
|
|
.. _Ask questions on Stackoverflow: http://stackoverflow.com/search?q=docker
|
|
.. _Join the conversation on Twitter: http://twitter.com/docker
|
|
|
|
Looking for something else to read? Checkout the :ref:`hello_world` example.
|