What is the main purpose of kube-system namespace?

[Qian Zhang]

Hi,

It seems "kube-system" namespace will be created by default, can anyone let me know what its main purpose is?

I see both kube-dns and dashboard should be created in "kube-system" namespace, but I do not know why. Is it because kube-dns and dashboard should be running on the master rather than on a node?

[Rodrigo Campos]

No, it's running on nodes, just as other pods. Do "kubectl get pods --all-namespaces -o wide" to see in which nodes they are running.

Namespaces can have defaults for the resources and limits a pod can have, and as the number of RCs, etc. So it's better to have them in a k8s namespaces and not mixed with all the rest of the pods.

Also, it's more clear and readable, etc.

[Matthias Rampke]

Hey,

as far as Kubernetes is concerned, it is not special.

The namespace is created when the cluster addons are deployed into the cluster; and some addons (namely, the logging ones) assume that it is so. Others, like DNS, don't care, for them it's just a namespace. If you really wanted to, you could modify all addons to use a different namespace, and never create kube-system, or even deploy each addon into its own namespace.[0]

Pods in that namespace are not scheduled differently.

/MR

[0] this is only true in self-managed clusters – in GKE for example they are managed for you and you can't modify them.

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[Qian Zhang]

I see the following code in https://github.com/kubernetes/kubernetes/blob/v1.2.4/pkg/api/types.go#L150:

    // NamespaceSystem is the system namespace where we place system components.

    NamespaceSystem string = "kube-system"

So the purpose of this namespace is to place system components. But I am not sure what are the system components, are kube-dns, dashboard and other add-ons system components?

[Rodrigo Campos]

On Thursday, May 26, 2016, Qian Zhang <zhq5...@gmail.com> wrote:

I see the following code in https://github.com/kubernetes/kubernetes/blob/v1.2.4/pkg/api/types.go#L150:

    // NamespaceSystem is the system namespace where we place system components.

    NamespaceSystem string = "kube-system"

So the purpose of this namespace is to place system components. But I am not sure what are the system components, are kube-dns, dashboard and other add-ons system components?

Yes