Containers break up apps into smaller packages of code, each bundled with all the basic system software the apps need to operate independently of whichever server plays host. This means programmers won’t have to rewrite the code for each new operating system and platform as an app evolves from a project on a laptop to a global hit with millions of users reached via enormous servers, says Jim Zemlin, executive director of the Linux Foundation, a nonprofit that oversees the open source Linux OS. “A developer will be able to write that software and deploy it without having to spend six months” rewriting it for broader and bigger systems, he says. Moving containers from one cloud provider to another is as simple as downloading them onto the new servers.
While market share data are tough to pin down, Docker set the early standard in container software, and the leading options among its dozen or so rivals include Warden, LXD, and CoreOS, according to researcher IDC. Many of the container makers, plus Google, are also refining competing versions of container orchestration software, the layer of programming that helps containers knit themselves together in the proper order to make an app run. Kubernetes, an open source program led by Google, is the early front-runner, says Larry Carvalho, an analyst at IDC.