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> How does Kubernetes not also result in the same? Here's the difference between kubernetes and ansible (and alikes) (and I'm over-simplifying a bit of course,

> How does Kubernetes not also result in the same? Here's the difference between kubernetes and ansible (and alikes) (and I'm over-simplifying a bit of course, but the idea is there) * With kubernetes, you write down the state you want your infrastructure to be in, and k8s figures out how to get there * With ansible, you write down how to get to the state you want and ansible runs those steps, and hopefully they end up in the same state. The issue is that if you run the same set of steps on a Debian linux distribution, and on a Ubuntu distribution, well, they might end up in a similar state, but they actually aren't; for starters: one is debian, the other is unbuntu.

dale_glass 5y ago
Ansible does try to do the 'write down the state you want your infrastructure to be in' thing. Eg, - name: "Ensure sshd is started and enabled on boot" systemd: state: started enabled: yes name: sshd You're not saying 'enable the sshd service', but 'the desired state for sshd is started and enabled'. But this is not perfect, because it's easy to eventually end up with imperative commands, like "run this script", or "Copy this file".
- kspacewalk2 5y ago
  That does not seem avoidable. I have never used kubernetes, but this seems highly suspect: >With kubernetes, you write down the state you want your infrastructure to be in, and k8s figures out how to get there My guess is that this devolves to "run this script" or "copy this file" in practice as well. Or it just becomes tautological, i.e. "here's the state I want the system to be in (and that means run this script and then copy this file over here, and don't forget to symlink it over there)". Am I wrong?
  - scrollaway 5y ago
    Yeah you're (mostly) incorrect. I recommend looking into terraform and how it handles state, that will give you a better idea of how it's possible to do infrastructure in a "this is what i want, figure out how to get there" way. Terraform isn't the best implementation of it; k8s has full control over the infra so it's even more powerful in that regard.
  - JeremyNT 5y ago
    Kubernetes itself tries Very Hard to completely abstract those implementation details. Like, obsessively hard. You (assuming "you" are somebody who wants to run something in k8s) should never need to know or care what it's doing "under the hood" to run your pod in the way you say. What's happened though is that Kubernetes expects for you to hand it an artifact that encapsulates all of the messy steps required before it can "run the thing." In practice that means the "run the script and symlink stuff" kind of glue is still present, it's just moved into Dockerfiles (which are, more or less, just fancy shell scripts themselves), build scripts, CI/CD pipelines, and startup scripts. The big shift is more that the responsibility for managing this junk is pushed, organizationally, onto whoever knows how to operate the actual application (because they'll be creating the Dockerfile). Usually that's a developer. So it's not wrong to say: > With kubernetes, you write down the state you want your infrastructure to be in, and k8s figures out how to get there But it's not really a complete explanation, because it assumes you've already gotten to the point that you've bundled an artifact up that will "do the right thing" when Kubernetes provides the fundamental pieces of infrastructure you define in your template.

dale_glass 5y ago

Ansible does try to do the 'write down the state you want your infrastructure to be in' thing. Eg, - name: "Ensure sshd is started and enabled on boot" systemd: state: started enabled: yes name: sshd You're not saying 'enable the sshd service', but 'the desired state for sshd is started and enabled'. But this is not perfect, because it's easy to eventually end up with imperative commands, like "run this script", or "Copy this file".

kspacewalk2 5y ago
That does not seem avoidable. I have never used kubernetes, but this seems highly suspect: >With kubernetes, you write down the state you want your infrastructure to be in, and k8s figures out how to get there My guess is that this devolves to "run this script" or "copy this file" in practice as well. Or it just becomes tautological, i.e. "here's the state I want the system to be in (and that means run this script and then copy this file over here, and don't forget to symlink it over there)". Am I wrong?
- scrollaway 5y ago
  Yeah you're (mostly) incorrect. I recommend looking into terraform and how it handles state, that will give you a better idea of how it's possible to do infrastructure in a "this is what i want, figure out how to get there" way. Terraform isn't the best implementation of it; k8s has full control over the infra so it's even more powerful in that regard.
- JeremyNT 5y ago
  Kubernetes itself tries Very Hard to completely abstract those implementation details. Like, obsessively hard. You (assuming "you" are somebody who wants to run something in k8s) should never need to know or care what it's doing "under the hood" to run your pod in the way you say. What's happened though is that Kubernetes expects for you to hand it an artifact that encapsulates all of the messy steps required before it can "run the thing." In practice that means the "run the script and symlink stuff" kind of glue is still present, it's just moved into Dockerfiles (which are, more or less, just fancy shell scripts themselves), build scripts, CI/CD pipelines, and startup scripts. The big shift is more that the responsibility for managing this junk is pushed, organizationally, onto whoever knows how to operate the actual application (because they'll be creating the Dockerfile). Usually that's a developer. So it's not wrong to say: > With kubernetes, you write down the state you want your infrastructure to be in, and k8s figures out how to get there But it's not really a complete explanation, because it assumes you've already gotten to the point that you've bundled an artifact up that will "do the right thing" when Kubernetes provides the fundamental pieces of infrastructure you define in your template.