Docker: Its a tool that helps you to pack, ship and run any application as a light-weight Linux container. More on https://www.docker.io/
Works best on Linux kernel 3.8 Ubuntu 12.04 precise has 3.2 and needs to be upgraded.
Install Docker with on Ubuntu 12.04:
sudo apt-get update
sudo apt-get install linux-image-generic-lts-raring linux-headers-generic-lts-raring
sudo reboot
To check docker version:
sudo docker version
Client version: 0.11.1
Client API version: 1.11
Go version (client): go1.2.1
Git commit (client): fb99f99
Server version: 0.11.1
Server API version: 1.11
Git commit (server): fb99f99
Go version (server): go1.2.1
Last stable version: 0.11.1
To check info about docker installed:
sudo docker info
Containers: 1
Images: 9
Storage Driver: aufs
Root Dir: /var/lib/docker/aufs
Dirs: 11
Execution Driver: native-0.2
Kernel Version: 3.11.0-20-generic
WARNING: No swap limit support
To pull an existing docker image:
sudo docker pull <imagename>
sudo docker pull busybox
HelloWorld in docker:
sudo docker run busybox echo HelloWorld
Search for an existing image in the index:
docker search <image-name>
sudo docker search stackbrew/ubuntu
NAME DESCRIPTION STARS OFFICIAL TRUSTED
stackbrew/ubuntu Barebone ubuntu images 36
jprjr/stackbrew-node A stackbrew/ubuntu-based image for Docker,... 2 [OK]
hcvst/erlang Erlang R14B04 based on stackbrew/ubuntu 0 [OK]
stackbrew/ubuntu-upstart 0
Pull an existing image:
sudo docker pull ubuntu
Pulling repository ubuntu
a7cf8ae4e998: Pulling dependent layers
3db9c44f4520: Downloading [=================> ] 22.18 MB/63.51 MB 2m19s
74fe38d11401: Pulling dependent layers
316b678ddf48: Pulling dependent layers
99ec81b80c55: Pulling dependent layers
5e019ab7bf6d: Pulling dependent layers
511136ea3c5a: Download complete
6cfa4d1f33fb: Download complete
To the check the available images:
sudo docker images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
ubuntu 13.10 5e019ab7bf6d 2 weeks ago 180 MB
ubuntu saucy 5e019ab7bf6d 2 weeks ago 180 MB
ubuntu 12.04 74fe38d11401 2 weeks ago 209.6 MB
ubuntu precise 74fe38d11401 2 weeks ago 209.6 MB
ubuntu 12.10 a7cf8ae4e998 2 weeks ago 171.3 MB
ubuntu quantal a7cf8ae4e998 2 weeks ago 171.3 MB
ubuntu 14.04 99ec81b80c55 2 weeks ago 266 MB
ubuntu latest 99ec81b80c55 2 weeks ago 266 MB
ubuntu trusty 99ec81b80c55 2 weeks ago 266 MB
ubuntu raring 316b678ddf48 2 weeks ago 169.4 MB
ubuntu 13.04 316b678ddf48 2 weeks ago 169.4 MB
busybox latest 2d8e5b282c81 2 weeks ago 2.489 MB
ubuntu 10.04 3db9c44f4520 2 weeks ago 183 MB
ubuntu lucid 3db9c44f4520 2 weeks ago 183 MB
To run a command within an image:
docker run<image> command
sudo docker run ubuntu echo HelloWorld
HelloWorld
To install something on an ubuntu image
sudo docker run apt-get install <package>
find ID of the container
sudo docker ps -l
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
0dac167b178d ubuntu:14.04 ps aux 12 minutes ago Exited (0) 12 minutes ago goofy_bell
committing changes made to the images:
docker commit 0da firstcommit
723aa6ead77a14ff05cd2c640163345ec5a36fa9a4c757a6872a1ec919ab9345
To get log of the present container:
sudo docker logs 0dac167b178d
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.0 7132 644 ? Rs 09:10 0:00 ps aux
To inpect the details of an image
sudo docker inspect <id: 3-4 characters of id will work too>
sudo docker inspect 0da
<json output>
Push container image to the index
sudo docker push ubuntu
Creating Dockerfile:
All instructions in Dokerfile are in the form of
INSTRUCTION arguments
Instruction are not case sensitive but CAPS are recommended. The first instruction in any Dockerfile is the FROM instruction. The syntax is:
FROM <image>
FROM ubuntu
This will look for the image in Docker index. You can also search docker index by the command docker search
Next is the RUN instruction. The RUN instruction will execute any commands on the current image. After executing, it will also commit the changes. The committed image can be used for the next instructions from the Dockerfile. This way the committed changes form a layer of changes just like any other source code control system. Syntax of RUN command:
RUN <command>
RUN apt get install -y apache2
Here the RUN command is equivalent to docker run image command + docker commit container_id. Here image will be automatically replaced with the current image and container_id is the result of the previous commit.
Once you have created your Dockerfile you can use docker build to create you image from it. You can use the command in this way.
Create a Dockerfile with the content
FROM ubuntu
RUN apt-get install -y memcached
Save and close the file. If the file is in you r present directory:
docker build .
If the file in in some other location
docker build path/to/file
If passing through STDIN
docker build - < Dockerfile
If passing through github URL
docker build github.com/roshan4074
you can check the container with the command:
sudo docker images
To apply a tag to an image you the command: docker tag
sudo docker tag <container_id>
To comment a code use the "#' symbol followed by the text
To specify the contact info of the Maintainer of the Dockerfile:
MAINTAINER Name contact@email
To trigger a command as soon as a container starts, use ENTRYPOINT instruction
ENTRYPOINT echo "Hello, Container Started"
Another Format to use ENTRYPOINT Instrcution is
ENTRYPOINT ["echo", "Hello, Container Started"]
This is the preferred format
e.g
ENTRYPOINT ["wc", "-l"]
To execute a certain command by a particular user use the command USER
USER roshan
T open a particular port for a process use EXPOSE instruction
EXPOSE 8080
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