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This is precisely why I said the fact that someone would gloss over this is a red flag. The point is super critical. VMs are literally so hard to do correctly

This is precisely why I said the fact that someone would gloss over this is a red flag. The point is super critical. VMs are literally so hard to do correctly and in a performant fashion that parts of CPU instruction sets[0], and kernel subsystems (KVM[1]) were created to make them easier to run. Containers, in contrast are literally a few flags and a bunch of in-kernel antics. A few people, notably Liz Rice and Jessie Frazelle have given talks on how to make containers from scratch that are very illuminating for those that are interested: https://www.youtube.com/watch?v=HPuvDm8IC-4 https://www.youtube.com/watch?v=HPuvDm8IC-4 https://www.youtube.com/watch?v=cYsVvV1aVss https://www.youtube.com/watch?v=cYsVvV1aVss [0]: https://en.wikipedia.org/wiki/X86_virtualization https://en.wikipedia.org/wiki/X86_virtualization [1]: https://en.wikipedia.org/wiki/Kernel-based_Virtual_Machine https://en.wikipedia.org/wiki/Kernel-based_Virtual_Machine

panpanna 7y ago
Containers are "easy" because they are backed by tons of kennel code (cgroups, namespaces and basically a small part of many other subsystems). You can actually create containers from the shell! VMs are "hard" because you start with nothing save some very low-level help from the hardware.
- hardwaresofton 7y ago
  Also, I want to be clear that I'm using "simple" and "easy" in the rick hickey sense of the words, as in "simple" has more to do with what a thing is made of, and "easy" has more to do with ease of use, taking available tooling/familiarity and context into mind. What I should have made clearer was that I think containers are both easier and simpler than VMs. There are both less moving parts (I haven't looked, but I assume less code), and containers are easier to get started with than VMs (set some flags on some syscalls versus make sure you buy the right CPU).
  - panpanna 7y ago
    Fair enough, but don't forget there are some extremely simple hypervisor implementations out there too.

panpanna 7y ago

Containers are "easy" because they are backed by tons of kennel code (cgroups, namespaces and basically a small part of many other subsystems). You can actually create containers from the shell! VMs are "hard" because you start with nothing save some very low-level help from the hardware.

hardwaresofton 7y ago
Also, I want to be clear that I'm using "simple" and "easy" in the rick hickey sense of the words, as in "simple" has more to do with what a thing is made of, and "easy" has more to do with ease of use, taking available tooling/familiarity and context into mind. What I should have made clearer was that I think containers are both easier and simpler than VMs. There are both less moving parts (I haven't looked, but I assume less code), and containers are easier to get started with than VMs (set some flags on some syscalls versus make sure you buy the right CPU).
- panpanna 7y ago
  Fair enough, but don't forget there are some extremely simple hypervisor implementations out there too.