Docker: the Linux container runtime =================================== Docker complements LXC with a high-level API which operates at the process level. It runs unix processes with strong guarantees of isolation and repeatability across servers. Docker is a great building block for automating distributed systems: large-scale web deployments, database clusters, continuous deployment systems, private PaaS, service-oriented architectures, etc. * *Heterogeneous payloads*: any combination of binaries, libraries, configuration files, scripts, virtualenvs, jars, gems, tarballs, you name it. No more juggling between domain-specific tools. Docker can deploy and run them all. * *Any server*: docker can run on any x64 machine with a modern linux kernel - whether it's a laptop, a bare metal server or a VM. This makes it perfect for multi-cloud deployments. * *Isolation*: docker isolates processes from each other and from the underlying host, using lightweight containers. * *Repeatability*: because containers are isolated in their own filesystem, they behave the same regardless of where, when, and alongside what they run. Notable features ----------------- * Filesystem isolation: each process container runs in a completely separate root filesystem. * Resource isolation: system resources like cpu and memory can be allocated differently to each process container, using cgroups. * Network isolation: each process container runs in its own network namespace, with a virtual interface and IP address of its own. * Copy-on-write: root filesystems are created using copy-on-write, which makes deployment extremeley fast, memory-cheap and disk-cheap. * Logging: the standard streams (stdout/stderr/stdin) of each process container are collected and logged for real-time or batch retrieval. * Change management: changes to a container's filesystem can be committed into a new image and re-used to create more containers. No templating or manual configuration required. * Interactive shell: docker can allocate a pseudo-tty and attach to the standard input of any container, for example to run a throwaway interactive shell. Under the hood -------------- Under the hood, Docker is built on the following components: * The [cgroup](http://blog.dotcloud.com/kernel-secrets-from-the-paas-garage-part-24-c) and [namespacing](http://blog.dotcloud.com/under-the-hood-linux-kernels-on-dotcloud-part) capabilities of the Linux kernel; * [AUFS](http://aufs.sourceforge.net/aufs.html), a powerful union filesystem with copy-on-write capabilities; * The [Go](http://golang.org) programming language; * [lxc](http://lxc.sourceforge.net/), a set of convenience scripts to simplify the creation of linux containers. Install instructions ================== Installing on Ubuntu 12.04 and 12.10 ------------------------------------ 1. Install dependencies: ```bash sudo apt-get install lxc wget bsdtar curl sudo apt-get install linux-image-extra-`uname -r` ``` The `linux-image-extra` package is needed on standard Ubuntu EC2 AMIs in order to install the aufs kernel module. 2. Install the latest docker binary: ```bash wget http://get.docker.io/builds/$(uname -s)/$(uname -m)/docker-master.tgz tar -xf docker-master.tgz ``` 3. Run your first container! ```bash cd docker-master sudo ./docker pull base sudo ./docker run -i -t base /bin/bash ``` Consider adding docker to your `PATH` for simplicity. Installing on other Linux distributions --------------------------------------- Right now, the officially supported distributions are: * Ubuntu 12.04 (precise LTS) * Ubuntu 12.10 (quantal) Docker probably works on other distributions featuring a recent kernel, the AUFS patch, and up-to-date lxc. However this has not been tested. Some streamlined (but possibly outdated) installation paths' are available from the website: http://docker.io/documentation/ Usage examples ============== Running an interactive shell ---------------------------- ```bash # Download a base image docker pull base # Run an interactive shell in the base image, # allocate a tty, attach stdin and stdout docker run -i -t base /bin/bash ``` Starting a long-running worker process -------------------------------------- ```bash # Run docker in daemon mode (docker -d || echo "Docker daemon already running") & # Start a very useful long-running process JOB=$(docker run -d base /bin/sh -c "while true; do echo Hello world; sleep 1; done") # Collect the output of the job so far docker logs $JOB # Kill the job docker kill $JOB ``` Listing all running containers ------------------------------ ```bash docker ps ``` Expose a service on a TCP port ------------------------------ ```bash # Expose port 4444 of this container, and tell netcat to listen on it JOB=$(docker run -d -p 4444 base /bin/nc -l -p 4444) # Which public port is NATed to my container? PORT=$(docker port $JOB 4444) # Connect to the public port via the host's public address echo hello world | nc $(hostname) $PORT # Verify that the network connection worked echo "Daemon received: $(docker logs $JOB)" ``` Contributing to Docker ====================== Want to hack on Docker? Awesome! There are instructions to get you started on the website: http://docker.io/documentation/contributing/contributing.html They are probably not perfect, please let us know if anything feels wrong or incomplete. Note ---- We also keep the documentation in this repository. The website documentation is generated using sphinx using these sources. Please find it under docs/sources/ and read more about it https://github.com/dotcloud/docker/master/docs/README.md Please feel free to fix / update the documentation and send us pull requests. More tutorials are also welcome.