Docker and other Linux containers

Virtual machines are mainstream in cloud computing. The newest development on the this arena are fast and lightweight process virtualization.  Linux-based container infrastructure is an emerging cloud technology that provides its users an environment as close as possible to a standard Linux distribution.

Linux Containers and the Future Cloud article tells that as opposed to para-virtualization solutions (Xen) and hardware virtualization solutions (KVM), which provide virtual machines (VMs), containers do not create other instances of the operating system kernel. This brings advantage of containers over VMs is that starting and shutting down a container is much faster than starting and shutting down a VM. The idea of process-level virtualization in itself is not new (remember Solaris Zones and BSD jails).

All containers under a host are running under the same kernel. Basically, a container is a Linux process (or several processes) that has special features and that runs in an isolated environment, configured on the host.  Containerization is a way of packaging up applications so that they share the same underlying OS but are otherwise fully isolated from one another with their own CPU, memory, disk and network allocations to work within – going a few steps further than the usual process separation in Unix-y OSes, but not completely down the per-app virtual machine route. The underlying infrastructure of modern Linux-based containers consists mainly of two kernel features: namespaces and cgroups. Well known Linux container technologies are Docker, OpenVZ, Google containers, Linux-VServer and LXC (LinuX Containers).

Docker is an open-source project that automates the creation and deployment of containers. 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 started as an internal project by a Platform-as-a-Service (PaaS) company called dotCloud at the time, and now called Docker Inc. Docker is currently available only for Linux (Linux kernel 3.8 or above). It utilizes the LXC toolkit. It runs on distributions like Ubuntu 12.04, 13.04; Fedora 19 and 20; RHEL 6.5 and above; and on cloud platforms like Amazon EC2, Google Compute Engine and Rackspace.

Linux containers are turning to a way of packaging up applications and related software for movement over the network or Internet. You can create images by running commands manually and committing the resulting container, but you also can describe them with a Dockerfile. Docker images can be stored on a public repository. Docker is able to create a snapshot. Docker, the company that sponsors the open source project, is gaining allies in making its commercially supported Linux container format a de facto standard. Red Hat has woken up to the growth of Linux containers and has begun certifying applications running in the sandboxing tech.

Docker was last week a lot in IT news because Docker 1.0 has been released. Here are links to several articles on Docker:

Docker opens online port for packaging and shipping Linux containers

Docker, Open Source Application Container Platform, Has 1.0 Coming Out Party At Dockercon14

Google Embraces Docker, the Next Big Thing in Cloud Computing

Docker blasts into 1.0, throwing dust onto traditional hypervisors

Automated Testing of Hardware Appliances with Docker

Continuous Integration Using Docker, Maven and Jenkins

Getting Started with Docker

The best way to understand Docker is to try it!

This Docker thing looks interesting. Maybe I should spend some time testing it.



  1. Tomi Engdahl says:

    Containers and Kubernetes: What’s next?

    What’s ahead for container orchestration and Kubernetes? Here’s an expert peek

  2. Tomi Engdahl says:

    AWS’s container service gets support for Kubernetes

    AWS today announced its long-awaited support for the Kubernetes container orchestration system on top of its Elastic Container Service (ECS).

    Kubernetes has, of course, become something of a de facto standard for container orchestration. It already had the backing of Google (which incubated it), as well as Microsoft and virtually every other major cloud player.

  3. Tomi Engdahl says:

    Put Your IDE in a Container with Guacamole

    Put Your IDE in a Container
    Apache Guacamole is an incubating Apache project that enables X window applications to be exposed via HTML5 and accessed via a browser. This article shows how Guacamole can be run inside containers in an OpenShift Container Platform (OCP) cluster to enable Red Hat JBoss Developer Studio, the eclipse-based IDE for the JBoss middleware portfolio, to be accessed via a web browser. You’re probably thinking “Wait a minute… X windows applications in a container?” Yes, this is entirely possible and this post will show you how.

  4. Tomi Engdahl says:

    Getting started with Kubernetes

    Learn the basics of using the open source container management system with this easy tutorial.

    One of today’s most promising emerging technologies is paring containers with cluster management software such as Docker Swarm, Apache Mesos, and the popular Kubernetes. Kubernetes allows you to create a portable and scalable application deployment that can be scheduled, managed, and maintained easily. As an open source project, Kubernetes is continually being updated and improved, and it leads the way among container cluster management software.

  5. Tomi Engdahl says:

    What are Linux containers?

    Linux containers, in short, contain applications in a way that keep them isolated from the host system that they run on. Containers allow a developer to package up an application with all of the parts it needs, such as libraries and other dependencies, and ship it all out as one package. And they are designed to make it easier to provide a consistent experience as developers and system administrators move code from development environments into production in a fast and replicable way.

    In a way, containers behave like a virtual machine. To the outside world, they can look like their own complete system.

  6. Tomi Engdahl says:

    Why traditional storage doesn’t cut it in the new world of containers

    One approach is to use traditional storage appliances that support legacy applications. This is a natural inclination and assumption, but… the wrong one.

    Traditional storage appliances are based on decades-old architectures at this point and were not made for a container-based application world. These approaches also fail to offer the portability you need for your apps in today’s hybrid cloud world. Some of these traditional storage vendors offer additional software for your containers, which can be used as a go-between for these storage appliances and your container orchestration, but this approach still falls short as it is undermined by those same storage appliance limitations. This approach would also mean that storage for the container is provisioned separately from your container orchestration layer.

    There’s a better way! Storage containers containing storage software co-­reside with compute containers and serve storage to the compute containers from hosts that have local or direct-attached storage. Storage containers are deployed and provisioned using the same orchestration layer you’ve adopted in house (like Red Hat OpenShift Container Platform, which is Kubernetes based), just like compute containers.

  7. Tomi Engdahl says:

    Containerized Docker Application Lifecycle with Microsoft Platform and Tools

    Building containerized applications in an enterprise environment means that you need to have an end-to-end lifecycle so you are capable of delivering applications through Continuous Integration, Testing, Continuous Deployment to containers, and release management supporting multiple environments, while having solid production management and monitoring systems

  8. Tomi Engdahl says:

    Architecture of Red Hat OpenShift
    Container PaaS on Microsoft Azure

    An effective Platform-as-a-Service (PaaS) solution, in concert with containers and cloud management platforms can help your business deploy and operate applications more quickly, more flexibly and with higher quality. Red Hat OpenShift Container Platform on Microsoft Azure offers this agility and operational efficiency, without having to do your own integration.

  9. Tomi Engdahl says:

    Kubernetes 1.9 version bump is near – with APIs to extend the system
    Latest container wrangling bits should drop on Friday

    Assuming a handful of lingering issues can be resolved, the open-source Kubernetes project will introduce version 1.9 on Friday.

    In a phone interview with The Register, Aparna Sinha, special interest group (SIG) product management lead for Kubernetes and product manager at Google, singled out the general availability designation of the Apps/V1 Workloads API as the most notable aspect of the release.

    Workloads are computing resources used to manage and run containers in a cluster. The Apps Workloads API includes DaemonSet, Deployment, ReplicaSet, and StatefulSet; it’s distinct from the Batch Workloads API, which includes Job and CronJob and has yet to reach general availability.

    The general availability designation (V1) signals the API is robust enough for production usage and implies long-term backwards compatibility.

  10. Tomi Engdahl says:

    As Kubernetes surged in popularity in 2017, it created a vibrant ecosystem

    For a technology that the average person has probably never heard of, Kubernetes surged in popularity in 2017 with a particular group of IT pros who are working with container technology. Kubernetes is the orchestration engine that underlies how operations staff deploy and manage containers at scale.

  11. Tomi Engdahl says:

    5 reasons Kubernetes is the real deal

    Kubernetes will be at the heart of a large and growing percentage of infrastructure—on premises and in the cloud

  12. Tomi Engdahl says:

    Why mobile and containers are better together

    Containers are the next stop on enterprise IT’s mobile journey

    Industry analyst firm Gartner predicts that “by 2022, 70 percent of software interactions in enterprises will occur on mobile devices.” Even today, we see how many organizations have matured in their approach to mobile, from siloed one-off projects towards a more integrated and strategic approach that underpins all aspects of their digital journey – including culture, processes, technology, and business models. As mobile becomes table stakes, however, there are many considerations under the surface that need to be addressed by business and IT.

    Mobile alone is not sufficient in driving today’s digital business.

    When containers meet mobile
    The cloud emerged as a perfect pairing in the early stages of mobile adoption, supporting the agility, performance, and scalability required by enterprise-grade mobile apps. Now, container technologies take this a step further by supporting mobile workloads, which can run and be managed alongside other enterprise application workloads.

    Rather than treating mobile as a separate or special project with a dedicated technology stack, containers enable mobile to become part of modern enterprise application development. This enables mobile to run in its own environment in a container alongside other containerized workloads, such as integration, Internet of Things, web, business automation, and other workloads.

    But why are containers so important? Containers are technologies that allow applications to be packaged and isolated with their entire runtime environment — all dependencies, libraries, and configuration files needed to run, bundled into one convenient package, providing abstraction from the underlying infrastructure. They provide a neat solution to the problem of how to get software to run reliably when moved from one computing environment to another, e.g. from a developer’s laptop to a test environment, from staging to production, or from a physical machine in a data center to a virtual machine in a public or private cloud.

    The organizations that outdo their competitors in the next year and beyond will be able to marry cloud, container technologies, and modern application practices, such as DevOps and microservices architecture,

  13. Tomi Engdahl says:

    How to install and setup Docker on RHEL 7/CentOS 7

    How do I install and setup Docker container on an RHEL 7 (Red Hat Enterprise Linux) server? How can I setup Docker on a CentOS 7? How to install and use Docker CE on a CentOS Linux 7 server?

  14. Tomi Engdahl says:

    Google’s Kelsey Hightower talks Kubernetes and community

    Google’s popular developer advocate shares his thoughts on Kubernetes and why its community is key to its strength.

  15. Tomi Engdahl says:

    Container Images and Hosts: Selecting the Right Components

    We’ve published a new guide to help you select the right container hosts and images for you container workloads – whether it’s a single container running on a single host, or thousands of workloads running in a Kubernetes/OpenShift environment. Why? Because people don’t know what they don’t know and we are here to help.

  16. Tomi Engdahl says:

    First steps in integration of Windows and Linux Containers in OpenShift

    an interesting exploration on the integration of Microsoft Windows Containers and Linux Containers in an OCP Environment. This allows a true bi-modal IT technical implementation by combining the strength of both platforms into one cluster.


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