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Markus Lehtonen 8bb46345e7 docs: fix TOCs

Make table of contents in the pages cleaner and more readable by
dropping the main heading (H1 level) from TOCs. This was the original
intention with the usage of "no_toc" kramdown magic, which was broken,
however. The kramdown class magic needs to be specified on the line
immediately following the headinds, otherwise it has no effect. We need
to disable MD022 rule of mdlint as it does not understand this magic.

(cherry picked from commit 819f333118)

2021-10-04 16:45:54 +03:00

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title	layout	sort
Introduction	default	1

Introduction

{: .no_toc}

{: .no_toc .text-delta}

TOC {:toc}

This software enables node feature discovery for Kubernetes. It detects hardware features available on each node in a Kubernetes cluster, and advertises those features using node labels.

NFD consists of two software components:

nfd-master
nfd-worker

NFD-Master

NFD-Master is the daemon responsible for communication towards the Kubernetes API. That is, it receives labeling requests from the worker and modifies node objects accordingly.

NFD-Worker

NFD-Worker is a daemon responsible for feature detection. It then communicates the information to nfd-master which does the actual node labeling. One instance of nfd-worker is supposed to be running on each node of the cluster,

Feature discovery

Feature discovery is divided into domain-specific feature sources:

CPU
IOMMU
Kernel
Memory
Network
PCI
Storage
System
USB
Custom (rule-based custom features)
Local (hooks for user-specific features)

Each feature source is responsible for detecting a set of features which. in turn, are turned into node feature labels. Feature labels are prefixed with feature.node.kubernetes.io/ and also contain the name of the feature source. Non-standard user-specific feature labels can be created with the local and custom feature sources.

An overview of the default feature labels:

{
  "feature.node.kubernetes.io/cpu-<feature-name>": "true",
  "feature.node.kubernetes.io/custom-<feature-name>": "true",
  "feature.node.kubernetes.io/iommu-<feature-name>": "true",
  "feature.node.kubernetes.io/kernel-<feature name>": "<feature value>",
  "feature.node.kubernetes.io/memory-<feature-name>": "true",
  "feature.node.kubernetes.io/network-<feature-name>": "true",
  "feature.node.kubernetes.io/pci-<device label>.present": "true",
  "feature.node.kubernetes.io/storage-<feature-name>": "true",
  "feature.node.kubernetes.io/system-<feature name>": "<feature value>",
  "feature.node.kubernetes.io/usb-<device label>.present": "<feature value>",
  "feature.node.kubernetes.io/<file name>-<feature name>": "<feature value>"
}

Node annotations

NFD also annotates nodes it is running on:

Annotation	Description
[<instance>.]nfd.node.kubernetes.io/master.version	Version of the nfd-master instance running on the node. Informative use only.
[<instance>.]nfd.node.kubernetes.io/worker.version	Version of the nfd-worker instance running on the node. Informative use only.
[<instance>.]nfd.node.kubernetes.io/feature-labels	Comma-separated list of node labels managed by NFD. NFD uses this internally so must not be edited by users.
[<instance>.]nfd.node.kubernetes.io/extended-resources	Comma-separated list of node extended resources managed by NFD. NFD uses this internally so must not be edited by users.

NOTE: the --instance command line flag affects the annotation names

Unapplicable annotations are not created, i.e. for example master.version is only created on nodes running nfd-master.

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