Docker

if you and your friend have vm and want to sync up you may have to transfer 20gb of file. but with docker docker diff to check the difference then docker commit then docker push which will only be the change.

docker containers: are actual containers running the applications and includes os, user added files, and meta data

docker images: helps to launch docker containers

docker file: is a file containing instructions that help automate image creation

layer: each file system that is stacked when docker mounts rootfs.

Install docker using:

sudo rpm install docker

docker commands:

docker pull: pull a pre-built image from public repos

docker run: run in 3 modes background,foreground,interactive

docker logs: logs of running logs

docker commit: save container state

docker images: list of all images

docker diff: changes in files and directories

docker build: build docker images from

dockerfiles

docker inspect: low level info about containers

docker attach: interact with running container

docker kill: kill a container

it is beneficial to separate every server like in lamp have separate php, mysql,apache in diff containers

you can use a supervisor -n to it

docker file:

automates image creation process

set of instruction to create an image

syntax: instruction argument

how docker files different:

dockerfiles run in layers

after every command a new layer is created.

if there is a mistake in line 29 of 30 if you corect in docker then first 28 skip because already run and just resolving the issue.

Dockerfile commands:

MAINTAINER <author name> sets autho name

RUN <command> execute command

ADD <src><dest> copy files from one location to another

from local machine to inside docker

CMD[“executable”,”param1″,”param2″] provides default for executing container

EXPOSE <port>port on which container might get deprecated

ENTRYPOINT [“executable”,”param1″…] configure container as exe from where you want to start execution

WORKDIR /path set working dir

ENV <key> <value> set env variables

USER <uid> set UID for use when running an image

VOLUME [“/data”] enable access to a directory from a working container mount from host to docker

docker create   —–using dockerfile

Layering issue with dockerfile is that docker is restarted after every command you will losse any environment variable

If you want to run a if then you will have to write it on a single line.

you can override this in command line

if container when you execute CMD  and command as main command and if that command quits or goes in background.

boot2docker to bootstrap instead of chef

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