Docker Cookbook

part of a new movement that aims to build operating systems that provide just the
minimum required to run applications within containers. Philosophically, it tries to
simplify operation of the infrastructure, through a scalable, easily manageable OS that
provides a clear separation of concerns between operations and applications.
6.1 Discovering the CoreOS Linux Distribution
with Vagrant
Problem
You want to use the CoreOS Linux distribution to run your Docker containers, but
first you want to try CoreOS on your local machine.
Solution
Use 
Vagrant
to start a virtual machine in VirtualBox that will use CoreOS. Official
documentation that describes the entire process is 
available
. This recipe is a summary
of this documenation.
To run your first CoreOS virtual machine via Vagrant, you start by cloning a Git
repository
and then use 
vagrant up
. You will be able to 
ssh
to the started instance
and use Docker:
$ git clone https://github.com/coreos/coreos-vagrant.git
$ cd coreos-vagrant/
$ tree
.
├── CONTRIBUTING.md
├── MAINTAINERS
├── README.md
├── Vagrantfile
├── config.rb.sample
└── user-data.sample
0 directories, 6 files
170 | Chapter 6: Optimized Operating System Distributions for Docker

---

$ vagrant up
$ vagrant ssh
Last login: Mon Jan 12 10:39:30 2015 from 10.0.2.2
CoreOS alpha (557.0.0)
core@core-01 ~ $ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
CoreOS uses 
systemd
 as a Linux init system and aims to be a minimal distribution
with rolling upgrades that can be easily rolled back. Core packages should be installed
in the distribution directly, and applications should be fully contained in containers.
As such, there is no package manager in CoreOS. All services running in a CoreOS
instance are running as 
systemd
unit files, and you can 
interact
with them using com‐
mands like 
systemctl
or 
journalctl
:
$ systemctl list-units | grep docker |awk {'print $1'}
sys-devices-virtual-net-docker0.device
sys-subsystem-net-devices-docker0.device
var-lib-docker-btrfs.mount
docker.service
docker.socket
early-docker.target
$ journalctl -u docker.service
-- Logs begin at Mon 2015-01-12 10:39:15 UTC, ... --
Jan 12 10:39:34 core-01 systemd[1]: Starting Docker ...
Jan 12 10:39:34 core-01 systemd[1]: Started Docker ...
Jan 12 10:39:34 core-01 dockerd[876]: ... msg="+job serveapi(fd://)"
Jan 12 10:39:34 core-01 dockerd[876]: ... msg="+job init_networkdriver()"
Jan 12 10:39:34 core-01 dockerd[876]: ... msg="Listening for HTTP on fd ()"
Jan 12 10:39:34 core-01 dockerd[876]: ... msg="-job init_networkdriver() = OK (0)"
Jan 12 10:39:34 core-01 dockerd[876]: ... msg="Loading containers: start."
Jan 12 10:39:34 core-01 dockerd[876]: ... msg="Loading containers: done."
Jan 12 10:39:34 core-01 dockerd[876]: ... msg="docker daemon: 1.4.1 ..."
Jan 12 10:39:34 core-01 dockerd[876]: ... msg="+job acceptconnections()"
Jan 12 10:39:34 core-01 dockerd[876]: ... msg="-job acceptconnections() = OK (0)"
Jan 12 10:39:34 core-01 dockerd[876]: ... msg="GET /v1.16/containers/json"
Jan 12 10:39:34 core-01 dockerd[876]: ... msg="+job containers()"
Jan 12 10:39:34 core-01 dockerd[876]: ... msg="-job containers() = OK (0)"