Editing 1764: XKCDE

{{comic
| number    = 1764
| date      = November 25, 2016
| title     = XKCDE
| image     = xkcde.png
| titletext = 4. They unplug the root machine but the thousands of leaf VMs scatter in the wind and start spinning up new instances wherever they land
}}

==Explanation==

Randall has created a theoretical software environment named XKCDE (a portmanteau on xkcd and {{w|Collaborative development environment|CDE}} (Collaborative Development Environment)), which relies on the user creating a series of nested virtual machines inside each other (creating sort of a digital version of the {{w|Droste effect}}), which would likely cause extreme strain on the resources of the machine running it. This strain is explained in [[676: Abstraction]], at least for the normal case.

"Virtual Machines" are software which pretend to be PC hardware so that a "guest" operating system can run inside of them, under a "host" operating system. Nesting VMs is the process of making a guest also be a host to yet another guest. Generally this is considered wasteful of resources, especially beyond one or two layers deep, and is not done except in a test lab for very specific purposes.

"Containers" are a lighter form of PC abstraction. Instead of emulating the entire physical hardware, they only emulate the software stack sitting on top of the kernel. A containerisation tool will have its own standard library, software-stack and installed programs, but delegates all {{w|system calls|system calls}} to the host kernel.
This is more efficient because no hardware needs to be emulated, but the disadvantage is reduced isolation between host and guest. A misbehaving guest can induce kernel crashes that take the host with them.
The most well-known example of container software is {{w|Docker (software)|Docker}}.

Randall derives humour from repeating the nesting ''ad absurdum'' in a never-ending fractal of nested VMs, thus trapping the follower of the instruction forever, in a form of [[Nerd Sniping]]: Any external observer, such as your boss, who sees you doing this is likely to fire you for wasting company time (An outcome which is undesirable, though still better than being hit by a truck{{Citation needed}}). [https://xkcd.com/356/]

A software environment which disables both the machine it runs on and the user that runs it could be thought of as a useless machine.

The title-text is a joke on the words {{w|Tree (data structure)|root and leaf}} as used in abstract data structures, drawing an analogy of cutting down a tree (unplugging the root machine) scattering leaves (the nested VMs).
A subtle pun is hidden in 'spinning': several tree species use {{w|Samara (fruit)|spinning leaves}} to scatter their seeds. The {{w|Autorotation (helicopter)|autorotation}} due to the special shape of the leaves helps the seeds travel farther on the wind from their parent tree.  Randall mixes this meaning of 'spinning' with the act of "spinning up a VM", the colloquial phrasing for starting up a new instance of a guest virtual machine.
As a seed grows into a new tree where it lands, so apparently do the scattered VMs spin up new instances of themselves wherever they land.

In this case, a literal interpretation would be that turning off the computer the VMs are running on would make all the VMs without any VMs running in them propagate themselves through a network and install themselves on other computers, which at the end of the day would be a very inefficient method of creating a virus.

=== Real Life Practice ===
In 'normal' software development, spinning up a (single, non-nested) VM is a practice to ensure that the development environment is identical between developers, thus minimising hard-to-reproduce bugs due to local machine differences, such as [https://sourceforge.net/p/phpmyadmin/bugs/2343/#0e4a unmatching library versions], [http://www.moserware.com/2008/02/does-your-code-pass-turkey-test.html locale settings] or [http://askubuntu.com/questions/202857/cant-install-ati-proprietary-drivers-in-12-10 additional installed or missing software].
The single VM image is shared between all developers, who each spin up their own instance on their personal workstation.
In such cases, spinning up the VM is the first step in bringing up a local development environment, after which additional steps will usually instruct which programs to open, which configuration settings to change, etc.

Someone got [https://pcsteps.com/508-nested-virtualization 4 levels deep] with this.

==Transcript==
Installing the xkcd development environment

{| class="wikitable"
|
# Spin up a VM
# Spin up a VM inside that VM
# Continue spinning up nested VMs and containers until you get fired
|}

{{comic discussion}}

[[Category:Computers]]