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A VM is a good way to logically think about the containers, and I’m sure it’s the way the vast majority of people first think about them. Under the hood they a

A VM is a good way to logically think about the containers, and I’m sure it’s the way the vast majority of people first think about them. Under the hood they are simply a process isolated with namespaces, but their behavior on the outside feels like getting a VM.

FartyMcFarter 7y ago
But docker containers don't run their own kernel, which is a huge difference to a VM.
- 3fe9a03ccd14ca5 7y ago
  My point is that most people don’t even really know that’s how a VM works. They just think of a VM as a fresh sandbox where they can install and run stuff without deleting somebody else’s files or programs.
  - wrs 7y ago
    I'm hearing a repeated theme in your comments that people don't know much about how anything works, and that's supposedly OK. That's actually not OK. :)
    - kortex 7y ago
      No, that's how learning curves work. Until we can Matrix beam info into our skulljack, humans will spend a notrivial amount of time having to make do with using things while not fully understanding how they work. Unless one is 31337-rockstar-ninja-IQ150-programmer, the uptake of new skills is painful and takes time. The pedagogical process is important. It's totally OK to not know how anything works as long as you acknowledge that and are willing to learn.
      - wrs 7y ago
        I totally agree. That wasn’t the sentiment I was responding to, which sounded more like “nobody knows how that works, and they don’t really need to, so why are you wasting their time explaining how it actually works?”
- ignoramous 7y ago
  Neither does the JVM. Never a good idea to cling onto text-book definitions in this cloud industry full of buzz words.
  - _jal 7y ago
    It is never a good idea to not understand what you're doing, especially when the boundaries of who does what are moving around. I'm mostly an ops person in outlook, although I was a programmer for over a decade and write my share of code. The software-ization of infra is a good thing; unlike some ops folks, I don't find it threatening, I find it cool. What I find dismaying is some of the horrific stuff I catch before it gets to production, and what I do find threatening in a different way is worrying about what I miss. Moving OS-level dependency management in to dockerfiles? Great! How are you scanning that against CVEs? If you don't know you're not running a different kernel, I have a sneaking suspicion you're... not. And so on down the list of traditional ops practices I frequently discover developers had no idea even happened.
- kortex 7y ago
  So? There is nowhere in the docker-noob's workflow where the huge distinction between a docker container instance and a super light VM actually matters. Source: I knew nearly nothing about docker a year ago. And now I'm one of my company's go-to people for docker questions. The pain is still fresh in my mind and I see noob-pain every day :)
deleted 7y ago
[deleted]
0x8BADF00D 7y ago
Why not correct the misinformation then? Docker is nothing like a VM. It uses cgroups to reserve resources like CPU, memory, etc, and namespaces to isolate containers and their respective processes. VM applications will have to emulate hardware, so the kernel running under VM is able to enumerate hardware devices. Virtual machine emulates a computer with a full ISA.
- osipov 7y ago
  You are describing the specific technical details about how Docker containers are implemented. The analogy to VMs comes from the observation that VMs virtualize the hardware while containers virtualize the operating system.
  - deleted 7y ago
    [deleted]
  - Izkata 7y ago
    > The analogy to VMs comes from the observation that VMs virtualize the hardware while containers virtualize the operating system. Aaaand that off-the-cuff statement clears up the difference between them that I've been missing for months. Containers really do just look like a VM, if you don't know the implementation details and are just using them.
- mr_toad 7y ago
  > Virtual machine emulates a computer with a full ISA. You probably didn’t mean that they literally emulate an instruction set, because most modern hypervisors don’t emulate most instructions.
- viraptor 7y ago
  I wouldn't describe it this way if your goal is to correct misinformation. VMs can definitely pass through real hardware instead of emulation. (most often used for GPUs and network cards) And docker containers can use emulated hardware. (from the app's point of view) Normal processes can run emulated hardware via user-mode linux. The idea of a VM is so messy these days, it's best to define what kind of VM are you talking about first. (language? system? foreign hardware?)

FartyMcFarter 7y ago

But docker containers don't run their own kernel, which is a huge difference to a VM.

3fe9a03ccd14ca5 7y ago
My point is that most people don’t even really know that’s how a VM works. They just think of a VM as a fresh sandbox where they can install and run stuff without deleting somebody else’s files or programs.
- wrs 7y ago
  I'm hearing a repeated theme in your comments that people don't know much about how anything works, and that's supposedly OK. That's actually not OK. :)
  - kortex 7y ago
    No, that's how learning curves work. Until we can Matrix beam info into our skulljack, humans will spend a notrivial amount of time having to make do with using things while not fully understanding how they work. Unless one is 31337-rockstar-ninja-IQ150-programmer, the uptake of new skills is painful and takes time. The pedagogical process is important. It's totally OK to not know how anything works as long as you acknowledge that and are willing to learn.
    - wrs 7y ago
      I totally agree. That wasn’t the sentiment I was responding to, which sounded more like “nobody knows how that works, and they don’t really need to, so why are you wasting their time explaining how it actually works?”
ignoramous 7y ago
Neither does the JVM. Never a good idea to cling onto text-book definitions in this cloud industry full of buzz words.
- _jal 7y ago
  It is never a good idea to not understand what you're doing, especially when the boundaries of who does what are moving around. I'm mostly an ops person in outlook, although I was a programmer for over a decade and write my share of code. The software-ization of infra is a good thing; unlike some ops folks, I don't find it threatening, I find it cool. What I find dismaying is some of the horrific stuff I catch before it gets to production, and what I do find threatening in a different way is worrying about what I miss. Moving OS-level dependency management in to dockerfiles? Great! How are you scanning that against CVEs? If you don't know you're not running a different kernel, I have a sneaking suspicion you're... not. And so on down the list of traditional ops practices I frequently discover developers had no idea even happened.
kortex 7y ago
So? There is nowhere in the docker-noob's workflow where the huge distinction between a docker container instance and a super light VM actually matters. Source: I knew nearly nothing about docker a year ago. And now I'm one of my company's go-to people for docker questions. The pain is still fresh in my mind and I see noob-pain every day :)

deleted 7y ago

[deleted]

0x8BADF00D 7y ago

Why not correct the misinformation then? Docker is nothing like a VM. It uses cgroups to reserve resources like CPU, memory, etc, and namespaces to isolate containers and their respective processes. VM applications will have to emulate hardware, so the kernel running under VM is able to enumerate hardware devices. Virtual machine emulates a computer with a full ISA.

osipov 7y ago
You are describing the specific technical details about how Docker containers are implemented. The analogy to VMs comes from the observation that VMs virtualize the hardware while containers virtualize the operating system.
- deleted 7y ago
  [deleted]
- Izkata 7y ago
  > The analogy to VMs comes from the observation that VMs virtualize the hardware while containers virtualize the operating system. Aaaand that off-the-cuff statement clears up the difference between them that I've been missing for months. Containers really do just look like a VM, if you don't know the implementation details and are just using them.
mr_toad 7y ago
> Virtual machine emulates a computer with a full ISA. You probably didn’t mean that they literally emulate an instruction set, because most modern hypervisors don’t emulate most instructions.
viraptor 7y ago
I wouldn't describe it this way if your goal is to correct misinformation. VMs can definitely pass through real hardware instead of emulation. (most often used for GPUs and network cards) And docker containers can use emulated hardware. (from the app's point of view) Normal processes can run emulated hardware via user-mode linux. The idea of a VM is so messy these days, it's best to define what kind of VM are you talking about first. (language? system? foreign hardware?)