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Docker 1.0 Released
Graculus writes: "Docker, the company that sponsors the Docker.org open source project, is gaining allies in making its commercially supported Linux container format a de facto standard. Linux containers are a way of packaging up applications and related software for movement over the network or Internet. Once at their destination, they launch in a standard way and enable multiple containers to run under a single host operating system. 15 months and 8,741 commits after the earliest version was made public, Docker 1.0 has been released."
What is Docker?
Docker is an open platform for developers and sysadmins to build, ship, and run distributed applications.
How is this different from Virtual Machines?
Virtual Machines
Each virtualized application includes not only the application - which may be only 10s of MB - and the necessary binaries and libraries, but also an entire guest operating system - which may weigh 10s of GB.
Docker
The Docker Engine container comprises just the application and its dependencies. It runs as an isolated process in userspace on the host operating system, sharing the kernel with other containers. Thus, it enjoys the resource isolation and allocation benefits of VMs but is much more portable and efficient.
https://www.docker.com/whatisdocker/
The point is that don't create a VM. Containers runs applications in their own isolated (as in filesystem, memory, processes, network, users, etc) environment, but just one kernel, no hard reservation of memory or disk, it consumes resources pretty much like native apps.Another difference is at it just need the linux kernel, it runs where a linux kernel (modern enough, 2.6.38+) run, including inside VMs, so you can run them on amazon, google app engine, linode and a lot more.
What docker adds over LXC (Linux Containers) is using a copy-on-write filesystem (so if i get the filesystem for i.e. ubuntu for an app, and another application also tries to use the filesystem of ubuntu, the extra disk use is just what both changed, also cached disk works for both), using cgroups to be able to limit what resources the container can use, and a whole management system for deploying, managing, sharing, packaging and constructing. It enables you to i.e. build a container for some service (with all the servers it need to run, with the filesystem of the distribution you need, exposing just the ports you want to give services on), pack it, and use it as a single unit, deploying it in the amount of servers you want without worrying about conflicting libraries, required packages, or having the right distribution.
If you think that is something academical, Google heavily use containers in their cloud, creating 2 billon containers per week. They have their own container technology (LMCTFY, Let Me Contain That For You) but has been adopting lately Docker, and contributing not just code but also a lot of tools to manage containers in a cloud.