Resources

Docker is a powerful engine that can create both small systems that support individual development environments, and complex systems run by large corporations. Docker and Microservices Docker is an essential part of the trend toward microservices, where monolithic software systems are being broken up into smaller cooperating services. An example of evolving a system into microservices might be a software system where the login action is broken out from the main body of the program. Because it can be called … Continue reading “The Future of Docker”

Docker in the Quality Assurance Phase Docker can be used to create immutable servers, which are software systems that are dedicated to one purpose and are never changed once they are released from development. Updating or changing anything about an immutable server means replacing the server completely.   Testing immutable servers is much less complicated with Docker because there is nothing for the QA department to tweak on its own. The instructions for setting up and running the new software … Continue reading “How Should Docker Be Used? II”

As shown in the examples, Docker is driven by text commands, either issued on a command line or collected in a text file. This means Docker can integrate with any system that can emit text commands. With the popularity of DevOps increasing, more tools are available to integrate with Docker. Docker in the Development Phase Docker makes it easy to give developers private environments in which they develop their software. Docker also makes it easy to automate (and thus come … Continue reading “How Should Docker Be Used?”

So once a software system described by a Docker image has been created, how is that software run? First, install Docker on every machine on which the software will be run. Docker can be installed directly onto most Linux distributions, and onto Windows or Mac OSX systems. The systems Docker supports directly are listed at https://docs.docker.com/installation/. Next, tell the Docker software to read the image, then to construct a container that runs the software as described. A container is a … Continue reading “What Is a Docker Container?”

Docker images are stored in registries. There are two different kinds of Docker registries: public and private. Public registries, such as Docker hub, hold images that can build hundreds of software systems including: ● Apache or Nginx web servers ● MySQL, Cassandra, or MongoDB database servers ● Asterisk or Elasticsearch software packages Explore the public Docker images on the hub via the search command on any page at https://hub.docker.com.   Private registries hold Docker images that companies want to have complete … Continue reading “What Is a Docker Registry?”

Start with Ubuntu image. Install it if necessary FROM ubuntu MAINTAINER Maintenance Guy main_guy@email.com Run the normal commands to install apache under Ubuntu RUN apt-get update && apt-get -y install apache2 && apt-get clean #Set the appropriate environment variables Who is responsible for this Dockerfile ENV APACHE_RUN_USER www-data ENV APACHE_RUN_GROUP www-data ENV APACHE_LOG_DIR /var/log/apache2 # Set the directoriesRUN /bin/ln -sf ../sites-available/default-ssl \ /etc/apache2/sites-enabled/001-default-ssl RUN /bin/ln -sf ../mods-available/ssl.conf /etc/apache2/mods-enabled/ RUN /bin/ln -sf ../mods-available/ssl.load /etc/apache2/mods-enabled/ #Open the ports Apache uses to receive … Continue reading “Sample Docker File”

Lately, there has been a hot market growing around container orchestration. These products aim to ease the challenges of managing the dynamic nature of a container ecosphere. Container orchestration platforms empower users to easily deploy, manage, and scale multi-container-based applications in large clusters without having to worry about which server will host a particular container. Container cluster orchestration is also a very competitive space. Some of the most popular vendors are:• Kubernetes• Docker Swarm• Amazon ECS• Azure Container Service• Marathon• … Continue reading “Container Orchestration Platforms”

Lack of IsolationOne of the key worries about containers is that they don’t provide the same level of isolation to applications as virtual machines do. An advantage of using VMs is the abstraction at the physical hardware level that translates to individual kernels; these individual kernels limit the attack surface to the hypervisor. In theory, vulnerabilities in particular OS versions can’t be leveraged to compromise other VMs running on the same physical host. Since containers share the same kernel, admins … Continue reading “Disadvantages of Containers”

Low Startup TimeBecause they are so lightweight, containers can often be spun up in a fraction of a second. By contrast, a virtual machine may take several minutes to start up. That means containers can be provisioned whenever needed to react to spikes in demand, and shut down when no longer required, allowing resources to be used more efficiently. Research shows that the average lifespan of a container is 2.5 days, compared to 15 days for a cloud-based virtual machine, … Continue reading “Benefits of Containers: II”

Application PortabilityBuild once, run anywhere, is one of the key features of containers. A container wraps up an application with everything it needs to run, like configuration files and dependencies. This enables you to easily and reliably run applications on different environments such as your local desktop, physical servers, virtual servers, testing, staging, production environments, and public or private clouds.Fewer Resources RequiredUnlike virtual machines, containers do not have their own complete operating system. While a VM often measures several gigabytes … Continue reading “Benefits of Containers: I”