Docker is an open platform for developers and sysadmins to build, ship, and run distributed applications. Consisting of Docker Engine, a portable, lightweight runtime and packaging tool, and Docker Hub, a cloud service for sharing applications and automating workflows, Docker enables apps to be quickly assembled from components and eliminates the friction between development, QA, and production environments. As a result, IT can ship faster and run the same app, unchanged, on laptops, data center VMs, and any cloud.
and explanation from wikipedia
Docker is an open-source project that automates the deployment of applications inside software containers, by providing an additional layer of abstraction and automation of operating system–level virtualization on Linux.[2] Docker uses resource isolation features of the Linux kernel such as cgroups and kernel namespaces to allow independent "containers" to run within a single Linux instance, avoiding the overhead of starting virtual machines.[3]
Okay, that's the theory. If you want to quickly get an idea how docker work, you can try it here!
For people who has run virtual machine environment before, it may seem, hey isn't this very similar to the current virtual machine? But they are not the same really. See the software stack below virtual machines versus docker.
Next, we will install docker locally and the below illustration is using debian sid. If you run other linux distribution, you should read this page. First we will install and then start bash in the ubuntu container. Note that when pulling ubuntu image down, may take sometime which depending on your internet speed.
root@localhost:~# apt-get install docker.io
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
aufs-tools cgroupfs-mount libnih-dbus1 libnih1 makedev mountall plymouth
Suggested packages:
btrfs-tools debootstrap lxc rinse plymouth-themes
The following NEW packages will be installed:
aufs-tools cgroupfs-mount docker.io libnih-dbus1 libnih1 makedev mountall plymouth
0 upgraded, 8 newly installed, 0 to remove and 557 not upgraded.
Need to get 4,360 kB of archives.
After this operation, 21.6 MB of additional disk space will be used.
Do you want to continue? [Y/n] Y
Get:1 http://cdn.debian.net/debian/ unstable/main makedev all 2.3.1-93 [42.6 kB]
Get:2 http://cdn.debian.net/debian/ unstable/main plymouth amd64 0.9.0-9 [189 kB]
Get:3 http://cdn.debian.net/debian/ unstable/main libnih1 amd64 1.0.3-4.3 [127 kB]
Get:4 http://cdn.debian.net/debian/ unstable/main libnih-dbus1 amd64 1.0.3-4.3 [97.1 kB]
Get:5 http://cdn.debian.net/debian/ unstable/main mountall amd64 2.54 [68.3 kB]
Get:6 http://cdn.debian.net/debian/ unstable/main aufs-tools amd64 1:3.2+20130722-1.1 [92.9 kB]
Get:7 http://cdn.debian.net/debian/ unstable/main cgroupfs-mount all 1.1 [4,572 B]
Get:8 http://cdn.debian.net/debian/ unstable/main docker.io amd64 1.3.3~dfsg1-2 [3,739 kB]
Fetched 4,360 kB in 44s (97.8 kB/s)
Selecting previously unselected package makedev.
(Reading database ... 324961 files and directories currently installed.)
Preparing to unpack .../makedev_2.3.1-93_all.deb ...
Unpacking makedev (2.3.1-93) ...
Selecting previously unselected package plymouth.
Preparing to unpack .../plymouth_0.9.0-9_amd64.deb ...
Unpacking plymouth (0.9.0-9) ...
Selecting previously unselected package libnih1.
Preparing to unpack .../libnih1_1.0.3-4.3_amd64.deb ...
Unpacking libnih1 (1.0.3-4.3) ...
Selecting previously unselected package libnih-dbus1.
Preparing to unpack .../libnih-dbus1_1.0.3-4.3_amd64.deb ...
Unpacking libnih-dbus1 (1.0.3-4.3) ...
Selecting previously unselected package mountall.
Preparing to unpack .../mountall_2.54_amd64.deb ...
Unpacking mountall (2.54) ...
Selecting previously unselected package aufs-tools.
Preparing to unpack .../aufs-tools_1%3a3.2+20130722-1.1_amd64.deb ...
Unpacking aufs-tools (1:3.2+20130722-1.1) ...
Selecting previously unselected package cgroupfs-mount.
Preparing to unpack .../cgroupfs-mount_1.1_all.deb ...
Unpacking cgroupfs-mount (1.1) ...
Selecting previously unselected package docker.io.
Preparing to unpack .../docker.io_1.3.3~dfsg1-2_amd64.deb ...
Unpacking docker.io (1.3.3~dfsg1-2) ...
Processing triggers for man-db (2.7.0.2-5) ...
Processing triggers for dbus (1.8.12-3) ...
Setting up makedev (2.3.1-93) ...
/run/udev or .udevdb or .udev presence implies active udev. Aborting MAKEDEV invocation.
/run/udev or .udevdb or .udev presence implies active udev. Aborting MAKEDEV invocation.
/run/udev or .udevdb or .udev presence implies active udev. Aborting MAKEDEV invocation.
Setting up plymouth (0.9.0-9) ...
update-initramfs: deferring update (trigger activated)
update-rc.d: warning: start and stop actions are no longer supported; falling back to defaults
update-rc.d: warning: start and stop actions are no longer supported; falling back to defaults
Setting up libnih1 (1.0.3-4.3) ...
Setting up libnih-dbus1 (1.0.3-4.3) ...
Setting up mountall (2.54) ...
Setting up aufs-tools (1:3.2+20130722-1.1) ...
Setting up docker.io (1.3.3~dfsg1-2) ...
Adding group `docker' (GID 139) ...
Done.
Processing triggers for dbus (1.8.12-3) ...
Setting up cgroupfs-mount (1.1) ...
Processing triggers for initramfs-tools (0.117) ...
update-initramfs: Generating /boot/initrd.img-3.9-1-amd64
W: mdadm: /etc/mdadm/mdadm.conf defines no arrays.
W: mdadm: no arrays defined in configuration file.
Processing triggers for libc-bin (2.19-13) ...
root@localhost:~#
jason@localhost:~$ docker run -i -t ubuntu /bin/bash
2015/01/08 16:27:07 Post http:///var/run/docker.sock/v1.15/containers/create: dial unix /var/run/docker.sock: permission denied
jason@localhost:~$ sudo docker run -i -t ubuntu /bin/bash
Unable to find image 'ubuntu' locally
Pulling repository ubuntu
8eaa4ff06b53: Download complete
511136ea3c5a: Download complete
3b363fd9d7da: Download complete
607c5d1cca71: Download complete
f62feddc05dc: Download complete
Status: Downloaded newer image for ubuntu:latest
root@bedef9a17ac3:/# cat /etc/issue
Ubuntu 14.04.1 LTS \n \l
root@bedef9a17ac3:/# exit
jason@localhost:~$ sudo docker run ubuntu /bin/echo "hello world"
hello world
One would ask, why should I replace virtualbox to docker? There are four main points as outline in this article :
- Faster delivery of your applications
- Deploy and scale more easily
- Get higher density and run more workloads
- Faster deployment makes for easier management
If you think the above points are attracting, perhaps you should consider it and I leave these additional materials for your further exploration.
docker 101 video presentation.
remember to sign up
get the image from docker hub.
last but not least, documentation.
