CoreOS is a slimmed-down Linux distribution designed for easy creation of lots of OS instances. We like the concept.
CoreOS uses Docker to deploy applications in virtual containers; it also features a management communications bus, and group instance management.
Rackspace, Amazon Web Services (AWS), GoogleComputeEngine (GCE), and Brightbox are early cloud compute providers compatible with CoreOS and with specific deployment capacity for CoreOS. We tried Rackspace and AWS, and also some local "fleet" deployments.
CoreOS is skinny. We questioned its claims of less overall memory used, and wondered if it was stripped to the point of uselessness. We found that, yes, it saves a critical amount of memory (for some), and no, it's tremendously Spartan, but pretty useful in certain situations.
CoreOS has many similarities with Ubuntu. They're both free and GPLv3 licensed. Ubuntu 14.04 and CoreOS share the same kernel. Both are easily customizable, and no doubt you can make your own version. But CoreOS shuns about half of the processes that Ubuntu attaches by default.
If you're a critic of the bloatware inside many operating systems instances, CoreOS might be for you. In testing, we found it highly efficient. It's all Linux kernel-all-the-time, and if your organization is OS-savvy, you might like what you see in terms of performance and scale.
Security could be an issue
CoreOS uses curl for communications and SSL, and we recommend adding a standard, best-practices external SSL certificate authority for instance orchestration. Otherwise, you'll be madly generating and managing SSL relationships among a dynamic number of instances. CoreOS sends updates using signed certificates, too.
With this added SSL security control, your ability to scale efficiently is but a few scripts away. Here's the place where your investment in SSL certs and chains of authority back to a root cert is a good idea. It adds to the overhead, of course, to use SSL for what might otherwise be considered "trivial" instances. All the bits needed for rapid secure communications with SSL are there, and documented, and wagged in your face. Do it.
What You Get
CoreOS is a stripped-down Linux distro designed for rapidly deployed Spartan instance use. The concept is to have a distro that's bereft of the usual system memory and daemon leeches endemic to popular distributions and "ecosystems.'' This is especially true as popular distros get older and more "feature packed".
More available memory usually means more apps that can be run, and CoreOS is built to run them in containers. Along with its own communications bus--primitive as it is-- you get to run as many instances (and apps) as possible with the least amount of overhead and management drama.
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