Friday, December 12, 2014

Docker Usage Explained

Docker is a platform for developers and sysadmins to develop, ship, and run applications. Docker lets you quickly assemble applications from components and eliminates the friction that can come when shipping code. Docker lets you get your code tested and deployed into production as fast as possible.

Downloading a Docker image >>docker pull centos >>docker pull ubuntu
Running A Docker The -t and -i flags allocate a pseudo-tty and keep stdin open even if not attached. This will allow you to use the container like a traditional VM as long as the bash prompt is running. Let's launch an Ubuntu container and install Apache inside of it using the bash prompt: >>docker run -t -i ubuntu /bin/bash To Quit
Starting with docker 0.6.5, you can add -t to the docker run command, which will attach a pseudo-TTY. Then you can type Control-C to detach from the container without terminating it.If you use -t and -i then Control-C will terminate the container.When using -i with -t then you have to use Control-P Control-Q to detach without terminating.
Control-P Control-Q List the Dockers Running >>docker ps -a Enter a running docker >>docker exec -it [container-id] bash Once inside the Docker install the needed Items and Packages and configure the Services as needed. Now Quit the Docker using Control-P Control-Q To keep it running.
For Using Public Docker Registry, Register with Email Address and Username https://registry.hub.docker.com/
Committing the changes made into a new Image that can be used later. >>docker commit [container-id] <registered_username>/<Nameforimage> eg: core@coreos ~ $ docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 5adf005708db centos:latest "/bin/bash" 11 minutes ago Up 11 minutes thirsty_ritchie core@coreos ~ $ docker commit 5adf005708db rahulrajvn/centos-httpd b8810f9ca8d52a289c963f57824f575341324c353707a5b1f215840c9ea88ebe core@coreos ~ $ Now the Image named rahulrajvn/centos-httpd is present in the local machine if we need to create more of that Image in same sever we can use it. Pushing the Image to registered public Docker-io repo , While pusing we will be asked for Username and password. core@coreos ~ $ docker push rahulrajvn/centos-httpd The push refers to a repository [rahulrajvn/centos-httpd] (len: 1) Sending image list Please login prior to push: Username: rahulrajvn Password:******** Email: ****************** Login Succeeded The push refers to a repository [rahulrajvn/centos-httpd] (len: 1) Sending image list Pushing repository rahulrajvn/centos-httpd (1 tags) 511136ea3c5a: Image already pushed, skipping 5b12ef8fd570: Image already pushed, skipping 34943839435d: Image already pushed, skipping b8810f9ca8d5: Image successfully pushed Pushing tag for rev [b8810f9ca8d5] on {https://cdn-registry-1.docker.io/v1/repositories/rahulrajvn/centos-httpd/tags/latest} core@coreos ~ $ Download a image from a Public Repo We just need to call it using the account name and Image name . Here in below example we use account rahulrajvn and image centos-httpd. core@coreos2 ~ $ docker pull rahulrajvn/centos-httpd Pulling repository rahulrajvn/centos-httpd b8810f9ca8d5: Download complete 511136ea3c5a: Download complete 5b12ef8fd570: Download complete 34943839435d: Download complete Status: Downloaded newer image for rahulrajvn/centos-httpd:latest core@coreos2 ~ $ Network Access to 80 The default apache install will be running on port 80. To give our container access to traffic over port 80, we use the -p flag and specify the port on the host that maps to the port inside the container. In our case we want 80 for each, so we include -p 80:80 in our command: docker run -d -p 80:80 -it rahulrajvn/centos6 /bin/bash If we need to forward more ports we can do it by adding one more -p option. docker run -d -p 80:80 -p 2222:22 -it rahulrajvn/centos6 /bin/bash Listing the Images >>docker images Removing Images >>docker rmi <Image-ID>

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