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Welcome to our newest CodeRanch forum! This here place is where to go when you want to know about virtual machines, clouds, containers, and anything else that makes one physical machine look like many.

We hope to answer your questions about what these technologies are, how they differ, and when each solution is appropriate. Also, of course, how to set them up and configure them!

So pile on the questions, and we'll try and answer them and build up a wiki for the frequently-asked questions!


I'm the kickoff moderator - you may know me from the Tomcat and JavaServer faces forums, as well as a general nuisance around the ranch. I've been running virtual machines on my own in-house servers since Xen became a stock part of Linux and longer than that if you want to count my days in the Cretacous swamps of my mainframe era. I've also logged a lot of time on VMWare, done a little work in Microsoft's VM environment and presently run KVM.

My cloud credentials are thus: I run OpenStack in-house, have done a number of projects in the Amazon cloud, a few on Digital Ocean and a couple on no-name clouds.

I'm also a big fan of Container technology. All my newer services run in Docker containers. They're a great way to spin up new services in a hurry, and you can cross-connect containers for even more fun!

Also, I'm prepared to answer questions about provisioning systems, since when you start talking large numbers of servers and elastic servers, you generally want as much automated help as you can get. I run Red Hat Kickstart, Debian/Ubuntu preseed, Ansible and Puppet, with occasional forays into Chef and Salt. I've also done work with Vagrant and Packer, which are great ways to get VMs up and running in a hurry, on your local machines or in the cloud (or both!)

Anything else on the lines of virtualization technology, ask away. The qemu emulator does non-Intel CPUs, and is a great way to try out a new OS image for the Raspberry Pi without the need to actually have one handy. Solaris zones are fair game as well. And yes, I've run Solaris in VMs.

So have at it. We're prepared to make semi-intelligent noises on just about any facet of virtualization technology!
 
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Great idea for a new forum!

Tim, I have a suggestion. The forum can have a description line listing all the technologies that are covered here.
 
Marshal
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I worked with VMs in the early 1980's with VM/CMS running on System/370 hardware - was that part of your mainframe days as well?

In addition to a virtual console and disks, thee were also had virtual printers, virtual card punches and virtual card readers. You could transfer data between the VMs by punching virtual cards in one VM and transfering them to another VM's reader. VM/CMS had a interpreted language called REXX which not only gave control of the VM and its virtual peripherals, but also parts of the Control Program (like a hypervisor), allowing some pretty powerful applications to assembled with rather simple programming.

After a 20-something year break, I picked-up with XEN and then KVM - never used VMWare or anything as involved as OpenStack. I'm really interested in Docker and other containers but haven't tried anything hands-on yet.

I'm looking forward to both learning, and helping where I can. Thanks for setting this up.
 
Tim Holloway
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I've worked with mainframe VMs several times. In the eary 1980's I did some client support for my employer's product where the customer ran OS/VS1 as a VM. I used it at the University of Central Florida in the late 80's. One of the most fun ways has been on my own desktop machine. Project Hercules is an IBM mainframe emulator, capable of running any IBM OS - although the cost of licensing the newer releases is prohibitive. Still, I have an OS/MVS image that's about the same as what I used to support back circa 1986, a DOS/VS image newer than my 1970's college days and VM/CMS.

I haven't done ReXX on any of these platforms. It wasn't part of the package, although I believe that someone has made it available for Hercules users since then. ReXX was the favorite scripting language for the Commodore Amiga, though and I've also used it in OS/2.

One of the great things about virtualization technology is that when I get a new software product - or major update - dumped on me, there's usually a period of false starts where I learn the hard way what not to do. On conventional systems, that tended to mean a lot of lint was left around pretty much forevermore. With Vagrant, you can spin up and destroy an entire VM over and over until you get it right in a minimum of time and effort. With Docker you can do even better, since you're not doing a full OS install, just building on to a base OS image.

VMs are great and they went a long way towards solving problems like where we were blowing out circuit breakers because we had too many independent servers running at 3% loads (yes, I measured!). But containers are even better. A CentOS 6 VM image can take 1-4 GB of disk space, and the RAM footprint is going to run over 1 GB in many cases. Judicious use of qcow image stacking can lighten the disk burden, but Docker images can be much, much smaller.
 
Don't get me started about those stupid light bulbs.
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