Clean up kubeadm install guide (#17584)
* Fix link to cluster upgrade with kubeadm * Improve kubeadm container runtime install steps * Use tabs for Linux vs. non-Linux kubeadm CRI details * Tweak wording * Use dagger in place of double asterisk (Double asterisks don't render as well, and also can confuse Markdown-aware editors). * Move link inside preceding tabs Repeating the text makes life easier for readers.pull/19078/head
Tim Bannister
GitHub
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0da849d6d3
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e5eea5d8b9
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@ -100,9 +100,9 @@ update-alternatives --set iptables /usr/sbin/iptables-legacy
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| Protocol | Direction | Port Range | Purpose | Used By |
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|----------|-----------|-------------|-----------------------|-------------------------|
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| TCP | Inbound | 10250 | Kubelet API | Self, Control plane |
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| TCP | Inbound | 30000-32767 | NodePort Services** | All |
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| TCP | Inbound | 30000-32767 | NodePort Services† | All |
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** Default port range for [NodePort Services](/docs/concepts/services-networking/service/).
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† Default port range for [NodePort Services](/docs/concepts/services-networking/service/).
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Any port numbers marked with * are overridable, so you will need to ensure any
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custom ports you provide are also open.
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@ -116,35 +116,48 @@ documentation for the plugins about what port(s) those need.
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## Installing runtime {#installing-runtime}
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Since v1.6.0, Kubernetes has enabled the use of CRI, Container Runtime Interface, by default.
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To run containers in Pods, Kubernetes uses a
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{{< glossary_tooltip term_id="container-runtime" text="container runtime" >}}.
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Since v1.14.0, kubeadm will try to automatically detect the container runtime on Linux nodes
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by scanning through a list of well known domain sockets. The detectable runtimes and the
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socket paths, that are used, can be found in the table below.
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{{< tabs name="container_runtime" >}}
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{{% tab name="Linux nodes" %}}
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| Runtime | Domain Socket |
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|------------|----------------------------------|
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| Docker | /var/run/docker.sock |
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| containerd | /run/containerd/containerd.sock |
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| CRI-O | /var/run/crio/crio.sock |
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By default, Kubernetes uses the
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{{< glossary_tooltip term_id="cri" text="Container Runtime Interface">}} (CRI)
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to interface with your chosen container runtime.
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If both Docker and containerd are detected together, Docker takes precedence. This is
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needed, because Docker 18.09 ships with containerd and both are detectable.
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If any other two or more runtimes are detected, kubeadm will exit with an appropriate
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error message.
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If you don't specify a runtime, kubeadm automatically tries to detect an installed
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container runtime by scanning through a list of well known Unix domain sockets.
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The following table lists container runtimes and their associated socket paths:
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On non-Linux nodes the container runtime used by default is Docker.
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{{< table caption = "Container runtimes and their socket paths" >}}
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| Runtime | Path to Unix domain socket |
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|------------|-----------------------------------|
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| Docker | `/var/run/docker.sock` |
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| containerd | `/run/containerd/containerd.sock` |
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| CRI-O | `/var/run/crio/crio.sock` |
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{{< /table >}}
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If the container runtime of choice is Docker, it is used through the built-in
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`dockershim` CRI implementation inside of the `kubelet`.
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<br />
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If both Docker and containerd are detected, Docker takes precedence. This is
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needed because Docker 18.09 ships with containerd and both are detectable even if you only
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installed Docker.
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If any other two or more runtimes are detected, kubeadm exits with an error.
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Other CRI-based runtimes include:
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The kubelet integrates with Docker through the built-in `dockershim` CRI implementation.
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- [containerd/cri](https://github.com/containerd/cri) (CRI plugin built into containerd)
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- [cri-o](https://cri-o.io/)
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- [frakti](https://github.com/kubernetes/frakti)
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See [container runtimes](/docs/setup/production-environment/container-runtimes/)
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for more information.
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{{% /tab %}}
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{{% tab name="other operating systems" %}}
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By default, kubeadm uses {{< glossary_tooltip term_id="docker" >}} as the container runtime.
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The kubelet integrates with Docker through the built-in `dockershim` CRI implementation.
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See [container runtimes](/docs/setup/production-environment/container-runtimes/)
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for more information.
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{{% /tab %}}
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{{< /tabs >}}
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Refer to the [CRI installation instructions](/docs/setup/cri) for more information.
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## Installing kubeadm, kubelet and kubectl
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@ -170,7 +183,7 @@ For information about installing `kubectl`, see [Install and set up kubectl](/do
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{{< warning >}}
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These instructions exclude all Kubernetes packages from any system upgrades.
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This is because kubeadm and Kubernetes require
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[special attention to upgrade](/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade-1-14/).
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[special attention to upgrade](/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade/).
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{{</ warning >}}
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For more information on version skews, see:
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