Container technology, also known simply as wrapper technology, is a method of packaging an application so that it can run, with its dependencies, isolated from other processes. Major public cloud computing providers, including Amazon Web Services, Microsoft Azure, and Google Cloud Platform, have embraced container technology, with container software names including popular Docker options, Apache Mesos, rkt (pronounced "rocket" ) and Kubernetes. Container technology gets its name from the shipping industry. Instead of offering a unique way to ship each product, products are placed in steel shipping containers, which are already designed to be picked up by the crane at the dock, and inserted into the container designed to fit the standard size of the ship. container. In short, by standardizing the process and keeping items together, the container can be moved as a unit, and it costs less to do so. With computer container technology, this is a similar situation. Have you ever had the situation where a program works perfectly fine on one machine, but then turns into an awkward mess when you move on to the next? This can happen when migrating software from a developer's PC to a test server, or a physical server in an enterprise data center, to a server in the cloud. Problems arise when moving software due to differences between machine environments, such as installed operating system, SSL libraries, storage, security, and network topology. Just as the crane picks up the entire container as a unit to place it on the ship or truck for transport, making it easier to move, computer container technology accomplishes the same. Container technology contains not only software, but also dependencies, including libraries, binaries, and configuration files, all together, and are migrated as a unit, avoiding differences between machines, including differences in operating system and underlying hardware, that cause incompatibilities and crashes. Containers also make it easy to deploy software on a server.
Virtual machines
Before containers gained popularity, virtual machines were a prior approach. Here, one physical server could be used for multiple applications through virtualization technology, also known as a virtual machine, where each virtual machine contains the entire operating system as well as the entire ; application to run. The physical server then runs multiple virtual machines, each running its own operating system, with a single hypervisor emulation layer on top. By running multiple operating systems simultaneously, there is a lot of overhead on the server as resources are used and the number of virtual machines is limited to a few. In contrast, with container technology, the server runs a single operating system, because each container can share this single operating system with the other containers on the server. Shared OS parts are read-only so as not to interfere with other containers. This means that compared to virtual machines, containers require fewer server resources with reduced overhead and are significantly more efficient, so many more containers can be clustered on a single server. For example, while each virtual machine may require gigabytes of storage, each container running a similar program may require only megabytes.
How do containers work?
Containers are configured to do the work in a multi-container architecture, called a container cluster. In a Kubernetes container group, there is a single cluster master, with the other associated containers designated as nodes, which are the multiple worker machines. The role of the cluster master is to plan the workloads for the nodes, but also to manage their life cycle and updates. Container technology is not a new phenomenon and has long been an essential feature of Linux. Advances in container technology in recent years have become easier to use, and have been embraced by software developers for their simplicity and to avoid compatibility issues. They also allow you to break a program into small chunks, called microservices. The advantage of having the program as component microservices is that different teams can work separately on each of the containers as long as the interactions between the different containers are maintained, which facilitates faster software development. Finally, container technology allows for complete granular control of containers. While containers can run all kinds of software, legacy programs designed to run in a virtual machine don't migrate well to container technology. This old software running in a virtual machine can be installed on a cloud platform like Microsoft Azure, so containers aren't likely to completely replace virtual machines in the foreseeable future.
How do companies manage containers?
With so many programs running as containers, container management has become a requirement, and it's hard to see the impossibility of doing this task manually. Specialized container management software is required, and a popular open source solution is Kubernetes, which has several distributions, including Red Hat OpenShift. Container management software makes it easy to deploy containers and works well with the rapid deployment strategies of the DevOps philosophy. Another great feature of container technology is its flexibility. With a virtual machine, it takes several minutes to start up, just like the PC on your desktop starts up at the start of the day. In contrast, with container technology, since the operating system is already running on the server, a container can be started in seconds. This allows containers to start and stop as needed, to flex at a time of high demand, and to flex when they are not needed. Plus, if a container crashes, it can be quickly restarted so you can get back to work. This type of management is called container orchestration, and software like Docker Swarm can handle this type of orchestration and distribute tasks across groups of containers. Since multiple containers share the same operating system, there are concerns that container technology is less secure than a virtual machine. This is due to the fact that if there is a security flaw in the host kernel, it will affect multiple containers. Efforts have been made to make containers more secure. One approach includes Docker requiring a signing infrastructure to prevent unauthorized container startup. There is also container security software, such as Twistlock, that describes the behavior of a container and then stops a container that is not part of the expected profile.