Node Feature Discovery
This documentation is for Node Feature Discovery version that is no longer supported. Please upgrade and visit the documentation of the latest stable release.

# Customization guide

## Table of contents

## Overview

NFD provides multiple extension points for vendor and application specific labeling:

- `NodeFeature` (EXPERIMENTAL) objects can be used to communicate "raw" node features and node labeling requests to nfd-master.
- `NodeFeatureRule` objects provide a way to deploy custom labeling rules via the Kubernetes API
- `local` feature source of nfd-worker creates labels by executing hooks and reading files
- `custom` feature source of nfd-worker creates labels based on user-specified rules

## NodeFeature custom resource

EXPERIMENTAL NodeFeature objects provide a way for 3rd party extensions to advertise custom features, both as "raw" features that serve as input to NodeFeatureRule objects and as feature labels directly.

Note that RBAC rules must be created for each extension for them to be able to create and manipulate NodeFeature objects in their namespace.

Support for NodeFeature CRD API is enabled with the `-enable-nodefeature-api` command line flag. This flag must be specified for both nfd-master and nfd-worker as it will disable the gRPC communication between them.

### A NodeFeature example

Consider the following referential example:

    apiVersion: nfd.k8s-sigs.io/v1alpha1
    kind: NodeFeature
    metadata:
      labels:
        nfd.node.kubernetes.io/node-name: node-1
      name: vendor-features-for-node-1
    spec:
      # Features for NodeFeatureRule matching
      features:
        flags:
          vendor.flags:
            elements:
              feature-x: {}
              feature-y: {}
        attributes:
          vendor.config:
            elements:
              setting-a: "auto"
              knob-b: "123"
        instances:
          vendor.devices:
            elements:
            - attributes:
                model: "dev-1000"
                vendor: "acme"
            - attributes:
                model: "dev-2000"
                vendor: "acme"
      # Labels to be created
      labels:
        vendor-feature.enabled: "true"

The object targets node named `node-1`. It lists two "flag type" features under the `vendor.flags` domain, two "attribute type" features and uder the `vendor.config` domain and two "instance type" features under the `vendor.devices` domain. This features will not be directly affecting the node labels but they will be used as input when be `NodeFeatureRule` object are evaluated.

In addition the example requests directly the `feature.node.kubenernetes.io/vendor-feature.enabled=true` node label to be created.

The `nfd.node.kubernetes.io/node-name=<node-name>` must be in place for each NodeFeature objectt as NFD uses it to determine the node which it is targeting.

### Feature types

Features are divided into three different types:

- flag features: a set of names without any associated values, e.g. CPUID flags or loaded kernel modules
- attribute features: a set of names each of which has a single value associated with it (essentially a map of key-value pairs), e.g. kernel config flags or os release information
- instance features: a list of instances, each of which has multiple attributes (key-value pairs of their own) associated with it, e.g. PCI or USB devices

## NodeFeatureRule custom resource

`NodeFeatureRule` objects provide an easy way to create vendor or application specific labels and taints. It uses a flexible rule-based mechanism for creating labels and optionally taints based on node features.

### A NodeFeatureRule example

Consider the following referential example:

    apiVersion: nfd.k8s-sigs.io/v1alpha1
    kind: NodeFeatureRule
    metadata:
      name: my-sample-rule-object
    spec:
      rules:
        - name: "my sample rule"
          labels:
            "my-sample-feature": "true"
          matchFeatures:
            - feature: kernel.loadedmodule
              matchExpressions:
                dummy: {op: Exists}
            - feature: kernel.config
              matchExpressions:
                X86: {op: In, value: ["y"]}

It specifies one rule which creates node label `feature.node.kubenernetes.io/my-sample-feature=true` if both of the following conditions are true (`matchFeatures` implements a logical AND over the matchers):

- The `dummy` network driver module has been loaded
- X86 option in kernel config is set to `=y`

Create a `NodeFeatureRule` with a yaml file:

    kubectl apply -f https://raw.githubusercontent.com/kubernetes-sigs/node-feature-discovery/v0.12.5/examples/nodefeaturerule.yaml

Now, on X86 platforms the feature label appears after doing `modprobe dummy` on a system and correspondingly the label is removed after `rmmod dummy`. Note a re-labeling delay up to the sleep-interval of nfd-worker (1 minute by default).

See Label rule format for detailed description of available fields and how to write labeling rules.

### NodeFeatureRule tainting feature

This feature is experimental.

In some circumstances it is desirable keep nodes with specialized hardware away from running general workload and instead leave them for workloads that need the specialized hardware. One way to achieve it is to taint the nodes with the specialized hardware and add corresponding toleration to pods that require the special hardware. NFD offers node tainting functionality which is disabled by default. User can define one or more custom taints via the `taints` field of the NodeFeatureRule CR. The same rule-based mechanism is applied here and the NFD taints only rule matching nodes.

To enable the tainting feature, `--enable-taints` flag needs to be set to `true`. If the flag `--enable-taints` is set to `false` (i.e. disabled), taints defined in the NodeFeatureRule CR have no effect and will be ignored by the NFD master.

NOTE: Before enabling any taints, make sure to edit nfd-worker daemonset to tolerate the taints to be created. Otherwise, already running pods that do not tolerate the taint are evicted immediately from the node including the nfd-worker pod.

Example NodeFeatureRule with custom taints:

    apiVersion: nfd.k8s-sigs.io/v1alpha1
    kind: NodeFeatureRule
    metadata:
      name: my-sample-rule-object
    spec:
      rules:
        - name: "my sample taint rule"
          taints:
            - effect: PreferNoSchedule
              key: "feature.node.kubernetes.io/special-node"
              value: "true"
            - effect: NoExecute
              key: "feature.node.kubernetes.io/dedicated-node"
          matchFeatures:
            - feature: kernel.loadedmodule
              matchExpressions:
                dummy: {op: Exists}
            - feature: kernel.config
              matchExpressions:
                X86: {op: In, value: ["y"]}

In this example, if the `my sample taint rule` rule is matched, `feature.node.kubernetes.io/pci-0300_1d0f.present=true:NoExecute` and `feature.node.kubernetes.io/cpu-cpuid.ADX:NoExecute` taints are set on the node.

## Local feature source

NFD-Worker has a special feature source named `local` which is an integration point for external feature detectors. It provides a mechanism for pluggable extensions, allowing the creation of new user-specific features and even overriding built-in labels.

The `local` feature source has two methods for detecting features, hooks and feature files. The features discovered by the `local` source can further be used in label rules specified in `NodeFeatureRule` objects and the `custom` feature source.

NOTE: Be careful when creating and/or updating hook or feature files while NFD is running. In order to avoid race conditions you should write into a temporary file (outside the `source.d` and `features.d` directories), and, atomically create/update the original file by doing a filesystem move operation.

### A hook example

Consider a shell script `/etc/kubernetes/node-feature-discovery/source.d/my-hook.sh` having the following stdout output, or alternatively, a plaintext file `/etc/kubernetes/node-feature-discovery/features.d/my-features` having the following contents:

    my-feature.1
    my-feature.2=myvalue
    my.namespace/my-feature.3=456

This will translate into the following node labels:

    feature.node.kubernetes.io/my-feature.1: "true"
    feature.node.kubernetes.io/my-feature.2: "myvalue"
    my.namespace/my-feature.3: "456"

Note that in the example above `-extra-label-ns=my.namespace` must be specified on the nfd-master command line.

### Hooks

DEPRECATED The `local` source executes hooks found in `/etc/kubernetes/node-feature-discovery/source.d/`. The hook files must be executable and they are supposed to print all discovered features in `stdout`. With ELF binaries static linking is recommended as the selection of system libraries available in the NFD release image is very limited. Other runtimes currently supported by the NFD image are bash and perl.

`stderr` output of hooks is propagated to NFD log so it can be used for debugging and logging.

NFD tries to execute any regular files found from the hooks directory. Any additional data files the hook might need (e.g. a configuration file) should be placed in a separate directory in order to avoid NFD unnecessarily trying to execute them. A subdirectory under the hooks directory can be used, for example `/etc/kubernetes/node-feature-discovery/source.d/conf/`.

NOTE: Hooks are being DEPRECATED and will be removed in a future release. For backward compatibility, currently hooks are enabled by default and can be disabled via `sources.local.hooksEnabled` field in the worker configuration.

    sources:
      local:
        hooksEnabled: true  # true by default at this point

NOTE: NFD will blindly run any executables placed/mounted in the hooks directory. It is the user's responsibility to review the hooks for e.g. possible security implications.

NOTE: The minimal image variant only supports running statically linked binaries.

### Feature files

The `local` source reads files found in `/etc/kubernetes/node-feature-discovery/features.d/`.

### Input format

The hook stdout and feature files are expected to contain features in simple key-value pairs, separated by newlines:

    <name>[=<value>]

The label value defaults to `true`, if not specified.

Label namespace may be specified with `<namespace>/<name>[=<value>]`. The namespace must be explicitly allowed with the `-extra-label-ns` command line flag of nfd-master if using something else than `[<sub-ns>.]feature.node.kubernetes.io` or `[<sub-ns>.]profile.node.kubernetes.io`.

### Mounts

The standard NFD deployments contain `hostPath` mounts for `/etc/kubernetes/node-feature-discovery/source.d/` and `/etc/kubernetes/node-feature-discovery/features.d/`, making these directories from the host available inside the nfd-worker container.

#### Injecting labels from other pods

One use case for the hooks and/or feature files is detecting features in other Pods outside NFD, e.g. in Kubernetes device plugins. By using the same `hostPath` mounts for `/etc/kubernetes/node-feature-discovery/source.d/` and `/etc/kubernetes/node-feature-discovery/features.d/` in the side-car (e.g. device plugin) creates a shared area for deploying hooks and feature files to NFD. NFD will periodically scan the directories and run any hooks and read any feature files it finds.

## Custom feature source

The `custom` feature source in nfd-worker provides a rule-based mechanism for label creation, similar to the `NodeFeatureRule` objects. The difference is that the rules are specified in the worker configuration instead of a Kubernetes API object.

See worker configuration for instructions how to set-up and manage the worker configuration.

### An example custom feature source configuration

Consider the following referential configuration for nfd-worker:

    core:
      labelSources: ["custom"]
    sources:
      custom:
        - name: "my sample rule"
          labels:
            "my-sample-feature": "true"
          matchFeatures:
            - feature: kernel.loadedmodule
              matchExpressions:
                dummy: {op: Exists}
            - feature: kernel.config
              matchExpressions:
                X86: {op: In, value: ["y"]}

It specifies one rule which creates node label `feature.node.kubenernetes.io/my-sample-feature=true` if both of the following conditions are true (`matchFeatures` implements a logical AND over the matchers):

- The `dummy` network driver module has been loaded
- X86 option in kernel config is set to `=y`

In addition, the configuration only enables the `custom` source, disabling all built-in labels.

Now, on X86 platforms the feature label appears after doing `modprobe dummy` on a system and correspondingly the label is removed after `rmmod dummy`. Note a re-labeling delay up to the sleep-interval of nfd-worker (1 minute by default).

### Additional configuration directory

In addition to the rules defined in the nfd-worker configuration file, the `custom` feature source can read more configuration files located in the `/etc/kubernetes/node-feature-discovery/custom.d/` directory. This makes more dynamic and flexible configuration easier.

As an example, consider having file `/etc/kubernetes/node-feature-discovery/custom.d/my-rule.yaml` with the following content:

    - name: "my e1000 rule"
      labels:
        "e1000.present": "true"
      matchFeatures:
        - feature: kernel.loadedmodule
          matchExpressions:
            e1000: {op: Exists}

This simple rule will create `feature.node.kubenernetes.io/e1000.present=true` label if the `e1000` kernel module has been loaded.

The `samples/custom-rules` kustomize overlay sample contains an example for deploying a custom rule from a ConfigMap.

## Node labels

Feature labels have the following format:

    <namespace>/<name> = <value>

The namespace part (i.e. prefix) of the labels is controlled by nfd:

- All built-in labels use `feature.node.kubernetes.io`. This is also the default for user defined features that don't specify any namespace.
- User-defined labels are allowed to use:
  - `feature.node.kubernetes.io` and `profile.node.kubernetes.io` plus their sub-namespaces (e.g. `vendor.profile.node.kubernetes.io` and `sub.ns.profile.node.kubernetes.io`) by default
  - Additional namespaces may be enabled with the `-extra-label-ns` command line flag of nfd-master

## Label rule format

This section describes the rule format used in `NodeFeatureRule` objects and in the configuration of the `custom` feature source.

It is based on a generic feature matcher that covers all features discovered by nfd-worker. The rules rely on a unified data model of the available features and a generic expression-based format. Features that can be used in the rules are described in detail in available features below.

Take this rule as a referential example:

        - name: "my feature rule"
          labels:
            "my-special-feature": "my-value"
          matchFeatures:
            - feature: cpu.cpuid
              matchExpressions:
                AVX512F: {op: Exists}
            - feature: kernel.version
              matchExpressions:
                major: {op: In, value: ["5"]}
                minor: {op: Gt, value: ["1"]}
            - feature: pci.device
              matchExpressions:
                vendor: {op: In, value: ["8086"]}
                class: {op: In, value: ["0200"]}

This will yield `feature.node.kubenernetes.io/my-special-feature=my-value` node label if all of these are true (`matchFeatures` implements a logical AND over the matchers):

- the CPU has AVX512F capability
- kernel version is 5.2 or later (must be v5.x)
- an Intel network controller is present

### Fields

#### Name

The `.name` field is required and used as an identifier of the rule.

#### Labels

The `.labels` is a map of the node labels to create if the rule matches.

#### Labels template

The `.labelsTemplate` field specifies a text template for dynamically creating labels based on the matched features. See templating for details.

NOTE The `labels` field has priority over `labelsTemplate`, i.e. labels specified in the `labels` field will override anything originating from `labelsTemplate`.

### Taints

taints is a list of taint entries and each entry can have `key`, `value` and `effect`, where the `value` is optional. Effect could be `NoSchedule`, `PreferNoSchedule` or `NoExecute`. To learn more about the meaning of these effects, check out k8s documentation.

NOTE taints field is not available for the custom rules of nfd-worker and only for NodeFeatureRule objects.

#### Vars

The `.vars` field is a map of values (key-value pairs) to store for subsequent rules to use. In other words, these are variables that are not advertised as node labels. See backreferences for more details on the usage of vars.

#### Vars template

The `.varsTemplate` field specifies a text template for dynamically creating vars based on the matched features. See templating for details on using templates and backreferences for more details on the usage of vars.

NOTE The `vars` field has priority over `varsTemplate`, i.e. vars specified in the `vars` field will override anything originating from `varsTemplate`.

#### MatchFeatures

The `.matchFeatures` field specifies a feature matcher, consisting of a list of feature matcher terms. It implements a logical AND over the terms i.e. all of them must match in order for the rule to trigger.

          matchFeatures:
            - feature: <feature-name>
              matchExpressions:
                <key>:
                  op: <op>
                  value:
                    - <value-1>
                    - ...

The `.matchFeatures[].feature` field specifies the feature against which to match.

The `.matchFeatures[].matchExpressions` field specifies a map of expressions which to evaluate against the elements of the feature.

In each MatchExpression `op` specifies the operator to apply. Valid values are described below.

Operator | Number of values | Matches when
--- | --- | ---
`In` | 1 or greater | Input is equal to one of the values
`NotIn` | 1 or greater | Input is not equal to any of the values
`InRegexp` | 1 or greater | Values of the MatchExpression are treated as regexps and input matches one or more of them
`Exists` | 0 | The key exists
`DoesNotExist` | 0 | The key does not exists
`Gt` | 1 | Input is greater than the value. Both the input and value must be integer numbers.
`Lt` | 1 | Input is less than the value. Both the input and value must be integer numbers.
`GtLt` | 2 | Input is between two values. Both the input and value must be integer numbers.
`IsTrue` | 0 | Input is equal to "true"
`IsFalse` | 0 | Input is equal "false"

The `value` field of MatchExpression is a list of string arguments to the operator.

The behavior of MatchExpression depends on the feature type: for flag and attribute features the MatchExpression operates on the feature element whose name matches the `<key>`. However, for instance features all MatchExpressions are evaluated against the attributes of each instance separately.

#### MatchAny

The `.matchAny` field is a list of of `matchFeatures` matchers. A logical OR is applied over the matchers, i.e. at least one of them must match in order for the rule to trigger.

Consider the following example:

          matchAny:
            - matchFeatures:
                - feature: kernel.loadedmodule
                  matchExpressions:
                    kmod-1: {op: Exists}
                - feature: pci.device
                  matchExpressions:
                    vendor: {op: In, value: ["0eee"]}
                    class: {op: In, value: ["0200"]}
            - matchFeatures:
                - feature: kernel.loadedmodule
                  matchExpressions:
                    kmod-2: {op: Exists}
                - feature: pci.device
                  matchExpressions:
                    vendor: {op: In, value: ["0fff"]}
                    class: {op: In, value: ["0200"]}

This matches if kernel module kmod-1 is loaded and a network controller from vendor 0eee is present, OR, if kernel module kmod-2 has been loaded and a network controller from vendor 0fff is present (OR both of these conditions are true).

### Available features

The following features are available for matching:

Feature | Feature type | Elements | Value type | Description
--- | --- | --- | --- | ---
`cpu.cpuid` | flag |  |  | Supported CPU capabilities
|  | `<cpuid-flag>` |  | CPUID flag is present
`cpu.cstate` | attribute |  |  | Status of cstates in the intel_idle cpuidle driver
|  | `enabled` | bool | ‘true' if cstates are set, otherwise ‘false'. Does not exist of intel_idle driver is not active.
`cpu.model` | attribute |  |  | CPU model related attributes
|  | `family` | int | CPU family
|  | `vendor_id` | string | CPU vendor ID
|  | `id` | int | CPU model ID
`cpu.pstate` | attribute |  |  | State of the Intel pstate driver. Does not exist if the driver is not enabled.
|  | `status` | string | Status of the driver, possible values are ‘active' and ‘passive'
|  | `turbo` | bool | ‘true' if turbo frequencies are enabled, otherwise ‘false'
|  | `scaling` | string | Active scaling_governor, possible values are ‘powersave' or ‘performance'.
`cpu.rdt` | flag |  |  | Intel RDT capabilities supported by the system
|  | `<rdt-flag>` |  | RDT capability is supported, see RDT flags for details
`cpu.security` | attribute |  |  | Features related to security and trusted execution environments
|  | `sgx.enabled` | bool | `true` if Intel SGX (Software Guard Extensions) has been enabled, otherwise does not exist
|  | `se.enabled` | bool | `true` if IBM Secure Execution for Linux is available and has been enabled, otherwise does not exist
|  | `tdx.enabled` | bool | `true` if Intel TDX (Trusted Domain Extensions) is available on the host and has been enabled, otherwise does not exist
`cpu.sgx` | attribute |  |  | DEPRECATED: replaced by `cpu.security` feature
|  | `enabled` | bool | DEPRECATED: use `sgx.enabled` from `cpu.security` instead
`cpu.sst` | attribute |  |  | Intel SST (Speed Select Technology) capabilities
|  | `bf.enabled` | bool | `true` if Intel SST-BF (Intel Speed Select Technology - Base frequency) has been enabled, otherwise does not exist
`cpu.se` | attribute |  |  | DEPRECATED: replaced by `cpu.security` feature
|  | `enabled` | bool | DEPRECATED: use `se.enabled` from `cpu.security` instead
`cpu.topology` | attribute |  |  | CPU topology related features
|  | `hardware_multithreading` | bool | Hardware multithreading, such as Intel HTT, is enabled
`kernel.config` | attribute |  |  | Kernel configuration options
|  | `<config-flag>` | string | Value of the kconfig option
`kernel.loadedmodule` | flag |  |  | Loaded kernel modules
|  | `mod-name` |  | Kernel module `<mod-name>` is loaded
`kernel.selinux` | attribute |  |  | Kernel SELinux related features
|  | `enabled` | bool | `true` if SELinux has been enabled and is in enforcing mode, otherwise `false`
`kernel.version` | attribute |  |  | Kernel version information
|  | `full` | string | Full kernel version (e.g. ‘4.5.6-7-g123abcde')
|  | `major` | int | First component of the kernel version (e.g. ‘4')
|  | `minor` | int | Second component of the kernel version (e.g. ‘5')
|  | `revision` | int | Third component of the kernel version (e.g. ‘6')
`local.label` | attribute |  |  | Features from hooks and feature files, i.e. labels from the local feature source
|  | `<label-name>` | string | Label `<label-name>` created by the local feature source, value equals the value of the label
`memory.nv` | instance |  |  | NVDIMM devices present in the system
|  | `<sysfs-attribute>` | string | Value of the sysfs device attribute, available attributes: `devtype`, `mode`
`memory.numa` | attribute |  |  | NUMA nodes
|  | `is_numa` | bool | `true` if NUMA architecture, `false` otherwise
|  | `node_count` | int | Number of NUMA nodes
`network.device` | instance |  |  | Physical (non-virtual) network interfaces present in the system
|  | `name` | string | Name of the network interface
|  | `<sysfs-attribute>` | string | Sysfs network interface attribute, available attributes: `operstate`, `speed`, `sriov_numvfs`, `sriov_totalvfs`
`pci.device` | instance |  |  | PCI devices present in the system
|  | `<sysfs-attribute>` | string | Value of the sysfs device attribute, available attributes: `class`, `vendor`, `device`, `subsystem_vendor`, `subsystem_device`, `sriov_totalvfs`, `iommu_group/type`, `iommu/intel-iommu/version`
`storage.device` | instance |  |  | Block storage devices present in the system
|  | `name` | string | Name of the block device
|  | `<sysfs-attribute>` | string | Sysfs network interface attribute, available attributes: `dax`, `rotational`, `nr_zones`, `zoned`
`system.osrelease` | attribute |  |  | System identification data from `/etc/os-release`
|  | `<parameter>` | string | One parameter from `/etc/os-release`
`system.name` | attribute |  |  | System name information
|  | `nodename` | string | Name of the kubernetes node object
`usb.device` | instance |  |  | USB devices present in the system
|  | `<sysfs-attribute>` | string | Value of the sysfs device attribute, available attributes: `class`, `vendor`, `device`, `serial`
`rule.matched` | attribute |  |  | Previously matched rules
|  | `<label-or-var>` | string | Label or var from a preceding rule that matched

### Templating

Rules support template-based creation of labels and vars with the `.labelsTemplate` and `.varsTemplate` fields. These makes it possible to dynamically generate labels and vars based on the features that matched.

The template must expand into a simple format with `<key>=<value>` pairs separated by newline.

Consider the following example:

        labelsTemplate: |
          {{ range .pci.device }}vendor-{{ .class }}-{{ .device }}.present=true
          {{ end }}
        matchFeatures:
          - feature: pci.device
            matchExpressions:
              class: {op: InRegexp, value: ["^02"]}
              vendor: ["0fff"]

The rule above will create individual labels `feature.node.kubernetes.io/vendor-<class-id>-<device-id>.present=true` for each network controller device (device class starting with 02) from vendor 0ffff.

All the matched features of each feature matcher term under `matchFeatures` fields are available for the template engine. Matched features can be referenced with `{{ .<feature-name> }}` in the template, and the available data could be described in yaml as follows:

    .
      <key-feature>:
        - Name: <matched-key>
        - ...

      <value-feature>:
        - Name: <matched-key>
          Value: <matched-value>
        - ...

      <instance-feature>:
        - <attribute-1-name>: <attribute-1-value>
          <attribute-2-name>: <attribute-2-value>
          ...
        - ...

That is, the per-feature data is a list of objects whose data fields depend on the type of the feature:

- for flag features only ‘Name' is available
- for value features ‘Name' and ‘Value' are available
- for instance features all attributes of the matched instance are available

A simple example of a template utilizing name and value from an attribute feature:

        labelsTemplate: |
          {{ range .system.osrelease }}system-{{ .Name }}={{ .Value }}
          {{ end }}
        matchFeatures:
          - feature: system.osRelease
            matchExpressions:
              ID: {op: Exists}
              VERSION_ID.major: {op: Exists}

NOTE In case of matchAny is specified, the template is executed separately against each individual `matchFeatures` field and the final set of labels will be superset of all these separate template expansions. E.g. consider the following:

      - name: <name>
        labelsTemplate: <template>
        matchFeatures: <matcher#1>
        matchAny:
          - matchFeatures: <matcher#2>
          - matchFeatures: <matcher#3>

In the example above (assuming the overall result is a match) the template would be executed on matcher#1 as well as on matcher#2 and/or matcher#3 (depending on whether both or only one of them match). All the labels from these separate expansions would be created, i.e. the end result would be a union of all the individual expansions.

Rule templates use the Golang text/template package and all its built-in functionality (e.g. pipelines and functions) can be used. An example template taking use of the built-in `len` function, advertising the number of PCI network controllers from a specific vendor:

        labelsTemplate: |
          num-intel-network-controllers={{ .pci.device | len }}
        matchFeatures:
          - feature: pci.device
            matchExpressions:
              vendor: {op: In, value: ["8086"]}
              class: {op: In, value: ["0200"]}

Imaginative template pipelines are possible, but care must be taken in order to produce understandable and maintainable rule sets.

### Backreferences

Rules support referencing the output of preceding rules. This enables sophisticated scenarios where multiple rules are combined together to for more complex heuristics than a single rule can provide. The labels and vars created by the execution of preceding rules are available as a special `rule.matched` feature.

Consider the following configuration:

      - name: "my kernel label rule"
        labels:
          kernel-feature: "true"
        matchFeatures:
          - feature: kernel.version
            matchExpressions:
              major: {op: Gt, value: ["4"]}

      - name: "my var rule"
        vars:
          nolabel-feature: "true"
        matchFeatures:
          - feature: cpu.cpuid
            matchExpressions:
              AVX512F: {op: Exists}
          - feature: pci.device
            matchExpressions:
              vendor: {op: In, value: ["0fff"]}
              device: {op: In, value: ["1234", "1235"]}

      - name: "my high level feature rule"
        labels:
          high-level-feature: "true"
        matchFeatures:
          - feature: rule.matched
            matchExpressions:
              kernel-feature: {op: IsTrue}
              nolabel-feature: {op: IsTrue}

The `feature.node.kubernetes.io/high-level-feature = true` label depends on thw two previous rules.

Note that when referencing rules across multiple `NodeFeatureRule` objects attention must be paid to the ordering. `NodeFeatureRule` objects are processed in alphabetical order (based on their `.metadata.name`).

### Examples

Some more configuration examples below.

Match certain CPUID features:

      - name: "example cpuid rule"
        labels:
          my-special-cpu-feature: "true"
        matchFeatures:
          - feature: cpu.cpuid
            matchExpressions:
              AESNI: {op: Exists}
              AVX: {op: Exists}

Require a certain loaded kernel module and OS version:

      - name: "my multi-feature rule"
        labels:
          my-special-multi-feature: "true"
        matchFeatures:
          - feature: kernel.loadedmodule
            matchExpressions:
              e1000: {op: Exists}
          - feature: system.osrelease
            matchExpressions:
              NAME: {op: InRegexp, values: ["^openSUSE"]}
              VERSION_ID.major: {op: Gt, values: ["14"]}

Require a loaded kernel module and two specific PCI devices (both of which must be present):

      - name: "my multi-device rule"
        labels:
          my-multi-device-feature: "true"
        matchFeatures:
          - feature: kernel.loadedmodule
            matchExpressions:
              my-driver-module: {op: Exists}
          - pci.device:
              vendor: "0fff"
              device: "1234"
          - pci.device:
              vendor: "0fff"
              device: "abcd"

## Legacy custom rule syntax

DEPRECATED: use the new rule syntax instead.

The `custom` source supports the legacy `matchOn` rule syntax for backwards-compatibility.

To aid in making the legacy rule syntax clearer, we define a general and a per rule nomenclature, keeping things as consistent as possible.

### General nomenclature and definitions

    Rule        :Represents a matching logic that is used to match on a feature.
    Rule Input  :The input a Rule is provided. This determines how a Rule performs the match operation.
    Matcher     :A composition of Rules, each Matcher may be composed of at most one instance of each Rule.

### Custom features format (using the nomenclature defined above)

Rules are specified under `sources.custom` in the nfd-worker configuration file.

    sources:
      custom:
      - name: <feature name>
        value: <optional feature value, defaults to "true">
        matchOn:
        - <Rule-1>: <Rule-1 Input>
          [<Rule-2>: <Rule-2 Input>]
        - <Matcher-2>
        - ...
        - ...
        - <Matcher-N>
      - <custom feature 2>
      - ...
      - ...
      - <custom feature M>

The label is constructed by adding `custom-` prefix to the name field, label value defaults to `true` if not specified in the rule spec:

    feature.node.kubernetes.io/custom-<name> = <value>

### Matching process

Specifying Rules to match on a feature is done by providing a list of Matchers. Each Matcher contains one or more Rules.

Logical OR is performed between Matchers and logical AND is performed between Rules of a given Matcher.

### Rules

#### pciid rule

##### Nomenclature

    Attribute   :A PCI attribute.
    Element     :An identifier of the PCI attribute.

The PciId Rule allows matching the PCI devices in the system on the following Attributes: `class`,`vendor` and `device`. A list of Elements is provided for each Attribute.

##### Format

    pciId :
      class: [<class id>, ...]
      vendor: [<vendor id>,  ...]
      device: [<device id>, ...]

Matching is done by performing a logical OR between Elements of an Attribute and logical AND between the specified Attributes for each PCI device in the system. At least one Attribute must be specified. Missing attributes will not partake in the matching process.

#### UsbId rule

##### Nomenclature

    Attribute   :A USB attribute.
    Element     :An identifier of the USB attribute.

The UsbId Rule allows matching the USB devices in the system on the following Attributes: `class`,`vendor`, `device` and `serial`. A list of Elements is provided for each Attribute.

##### Format

    usbId :
      class: [<class id>, ...]
      vendor: [<vendor id>,  ...]
      device: [<device id>, ...]
      serial: [<serial>, ...]

Matching is done by performing a logical OR between Elements of an Attribute and logical AND between the specified Attributes for each USB device in the system. At least one Attribute must be specified. Missing attributes will not partake in the matching process.

#### LoadedKMod rule

##### Nomenclature

    Element     :A kernel module

The LoadedKMod Rule allows matching the loaded kernel modules in the system against a provided list of Elements.

##### Format

    loadedKMod : [<kernel module>, ...]

Matching is done by performing logical AND for each provided Element, i.e the Rule will match if all provided Elements (kernel modules) are loaded in the system.

#### CpuId rule

##### Nomenclature

    Element     :A CPUID flag

The Rule allows matching the available CPUID flags in the system against a provided list of Elements.

##### Format

    cpuId : [<CPUID flag string>, ...]

Matching is done by performing logical AND for each provided Element, i.e the Rule will match if all provided Elements (CPUID flag strings) are available in the system.

#### Kconfig rule

##### Nomenclature

    Element     :A Kconfig option

The Rule allows matching the kconfig options in the system against a provided list of Elements.

##### Format

    kConfig: [<kernel config option ('y' or 'm') or '=<value>'>, ...]

Matching is done by performing logical AND for each provided Element, i.e the Rule will match if all provided Elements (kernel config options) are enabled (`y` or `m`) or matching `=<value>` in the kernel.

#### Nodename rule

##### Nomenclature

    Element     :A nodename regexp pattern

The Rule allows matching the node's name against a provided list of Elements.

##### Format

    nodename: [ <nodename regexp pattern>, ... ]

Matching is done by performing logical OR for each provided Element, i.e the Rule will match if one of the provided Elements (nodename regexp pattern) matches the node's name.

### Legacy custom rule example

    custom:
      - name: "my.kernel.feature"
        matchOn:
          - loadedKMod: ["kmod1", "kmod2"]
      - name: "my.pci.feature"
        matchOn:
          - pciId:
              vendor: ["15b3"]
              device: ["1014", "1017"]
      - name: "my.usb.feature"
        matchOn:
          - usbId:
              vendor: ["1d6b"]
              device: ["0003"]
              serial: ["090129a"]
      - name: "my.combined.feature"
        matchOn:
          - loadedKMod : ["vendor_kmod1", "vendor_kmod2"]
            pciId:
              vendor: ["15b3"]
              device: ["1014", "1017"]
      - name: "vendor.feature.node.kubernetes.io/accumulated.feature"
        matchOn:
          - loadedKMod : ["some_kmod1", "some_kmod2"]
          - pciId:
              vendor: ["15b3"]
              device: ["1014", "1017"]
      - name: "my.kernel.featureneedscpu"
        matchOn:
          - kConfig: ["KVM_INTEL"]
          - cpuId: ["VMX"]
      - name: "my.kernel.modulecompiler"
        matchOn:
          - kConfig: ["GCC_VERSION=100101"]
            loadedKMod: ["kmod1"]
      - name: "profile.node.kubernetes.io/my-datacenter"
        value: "datacenter-1"
        matchOn:
          - nodename: [ "node-datacenter1-rack.*-server.*" ]

In the example above:

- A node would contain the label: `feature.node.kubernetes.io/custom-my.kernel.feature=true` if the node has `kmod1` AND `kmod2` kernel modules loaded.
- A node would contain the label: `feature.node.kubernetes.io/custom-my.pci.feature=true` if the node contains a PCI device with a PCI vendor ID of `15b3` AND PCI device ID of `1014` OR `1017`.
- A node would contain the label: `feature.node.kubernetes.io/custom-my.usb.feature=true` if the node contains a USB device with a USB vendor ID of `1d6b` AND USB device ID of `0003`.
- A node would contain the label: `feature.node.kubernetes.io/custom-my.combined.feature=true` if `vendor_kmod1` AND `vendor_kmod2` kernel modules are loaded AND the node contains a PCI device with a PCI vendor ID of `15b3` AND PCI device ID of `1014` or `1017`.
- A node would contain the label: `vendor.feature.node.kubernetes.io/accumulated.feature=true` if `some_kmod1` AND `some_kmod2` kernel modules are loaded OR the node contains a PCI device with a PCI vendor ID of `15b3` AND PCI device ID of `1014` OR `1017`.
- A node would contain the label: `feature.node.kubernetes.io/custom-my.kernel.featureneedscpu=true` if `KVM_INTEL` kernel config is enabled AND the node CPU supports `VMX` virtual machine extensions
- A node would contain the label: `feature.node.kubernetes.io/custom-my.kernel.modulecompiler=true` if the in-tree `kmod1` kernel module is loaded AND it's built with `GCC_VERSION=100101`.
- A node would contain the label: `profile.node.kubernetes.io/my-datacenter=datacenter-1` if the node's name matches the `node-datacenter1-rack.*-server.*` pattern, e.g. `node-datacenter1-rack2-server42`

Node Feature Discovery
v0.12

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This Software is under the terms of Apache License 2.0.