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前言

前面提到应用部署时，在实践工作中更多的是用kubectl apply。这节内容将介绍这两命令的具体用法，以及其配合使用的配置的编写。

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一、kubectl apply -f

-f是kubectl apply最常用的命令选项。通过文件名或控制台输入，对资源进行配置。接受JSON和YAML格式的描述文件。YAML格式更被推荐使用。

-f, --filename=[]: 包含配置信息的文件名，目录名或者URL。

示例：

# 将pod.json中的配置应用到pod
$ kubectl apply -f ./kube-config.yaml

# 将控制台输入的JSON配置应用到Pod
$ cat kube-config.yaml | kubectl apply -f -

二、k8s yaml配置文件

关于yaml的介绍不具体说了，文件后缀一般是.yaml或者.yml其语法格式如下：

大小写敏感
使用缩进表示层级关系
缩进不允许使用tab，只允许空格
缩进的空格数不重要，只要相同层级的元素左对齐即可
'#'表示注释

在k8s的配置清单文件中，需要掌握yaml语法中的键值对和数组。推荐yaml入门学习。

k8s的yaml配置主要分为四个部分:

• apiVersion
• kind
• metadata
• spec

如pod资源yaml示例：

apiVersion: v1 # API版本号，必须在`kubectl apiversion`中
kind: Pod  # 指定创建资源类型，资源类型可以是Deployment、Service等，根据实际情况决定。  
metadata:  # 元数据，包含一些meta信息，比如名称、namespace、标签等信息。
  name: nginx-test # 资源的名称，在同一个namespace空间中必须是唯一的
spec: # 资源规格，包括一些container，storage，volume以及其他k8s需要的参数。
  containers: # 容器列表
    - name: front-end # 容器名称
      image: nginx # 容器镜像
      ports:
        - containerPort: 80 # 容器的对外端口

1. apiVersion

表示指定api版本号，通常写v1，但是并不是写死的，可以执行kubectl api-versions命令查看，需要为其中一个。

$ kubectl api-versions
admissionregistration.k8s.io/v1
apiextensions.k8s.io/v1
apiregistration.k8s.io/v1
apps/v1
authentication.k8s.io/v1
authorization.k8s.io/v1
autoscaling/v1
autoscaling/v2
autoscaling/v2beta1
autoscaling/v2beta2
batch/v1
batch/v1beta1
certificates.k8s.io/v1
coordination.k8s.io/v1
discovery.k8s.io/v1
discovery.k8s.io/v1beta1
events.k8s.io/v1
events.k8s.io/v1beta1
flowcontrol.apiserver.k8s.io/v1beta1
flowcontrol.apiserver.k8s.io/v1beta2
networking.k8s.io/v1
node.k8s.io/v1
node.k8s.io/v1beta1
policy/v1
policy/v1beta1
rbac.authorization.k8s.io/v1
scheduling.k8s.io/v1
storage.k8s.io/v1
storage.k8s.io/v1beta1
v1

2. kind

表示该yaml定义的资源类型，k8s中资源有很多种，可以执行命令kubectl api-resources -o wide查看，但大多数并不常用。常用的资源主要包括Deployment，Services，Job等。

$ kubectl api-resources -o wide
NAME                              SHORTNAMES   APIVERSION                             NAMESPACED   KIND                             VERBS
bindings                                       v1                                     true         Binding                          [create]
componentstatuses                 cs           v1                                     false        ComponentStatus                  [get list]
configmaps                        cm           v1                                     true         ConfigMap                        [create delete deletecollection get list patch update watch]
endpoints                         ep           v1                                     true         Endpoints                        [create delete deletecollection get list patch update watch]
events                            ev           v1                                     true         Event                            [create delete deletecollection get list patch update watch]
limitranges                       limits       v1                                     true         LimitRange                       [create delete deletecollection get list patch update watch]
namespaces                        ns           v1                                     false        Namespace                        [create delete get list patch update watch]
nodes                             no           v1                                     false        Node                             [create delete deletecollection get list patch update watch]
persistentvolumeclaims            pvc          v1                                     true         PersistentVolumeClaim            [create delete deletecollection get list patch update watch]
persistentvolumes                 pv           v1                                     false        PersistentVolume                 [create delete deletecollection get list patch update watch]
pods                              po           v1                                     true         Pod                              [create delete deletecollection get list patch update watch]
podtemplates                                   v1                                     true         PodTemplate                      [create delete deletecollection get list patch update watch]
replicationcontrollers            rc           v1                                     true         ReplicationController            [create delete deletecollection get list patch update watch]
resourcequotas                    quota        v1                                     true         ResourceQuota                    [create delete deletecollection get list patch update watch]
secrets                                        v1                                     true         Secret                           [create delete deletecollection get list patch update watch]
serviceaccounts                   sa           v1                                     true         ServiceAccount                   [create delete deletecollection get list patch update watch]
services                          svc          v1                                     true         Service                          [create delete deletecollection get list patch update watch]
mutatingwebhookconfigurations                  admissionregistration.k8s.io/v1        false        MutatingWebhookConfiguration     [create delete deletecollection get list patch update watch]
validatingwebhookconfigurations                admissionregistration.k8s.io/v1        false        ValidatingWebhookConfiguration   [create delete deletecollection get list patch update watch]
customresourcedefinitions         crd,crds     apiextensions.k8s.io/v1                false        CustomResourceDefinition         [create delete deletecollection get list patch update watch]
apiservices                                    apiregistration.k8s.io/v1              false        APIService                       [create delete deletecollection get list patch update watch]
controllerrevisions                            apps/v1                                true         ControllerRevision               [create delete deletecollection get list patch update watch]
daemonsets                        ds           apps/v1                                true         DaemonSet                        [create delete deletecollection get list patch update watch]
deployments                       deploy       apps/v1                                true         Deployment                       [create delete deletecollection get list patch update watch]
replicasets                       rs           apps/v1                                true         ReplicaSet                       [create delete deletecollection get list patch update watch]
statefulsets                      sts          apps/v1                                true         StatefulSet                      [create delete deletecollection get list patch update watch]
tokenreviews                                   authentication.k8s.io/v1               false        TokenReview                      [create]
localsubjectaccessreviews                      authorization.k8s.io/v1                true         LocalSubjectAccessReview         [create]
selfsubjectaccessreviews                       authorization.k8s.io/v1                false        SelfSubjectAccessReview          [create]
selfsubjectrulesreviews                        authorization.k8s.io/v1                false        SelfSubjectRulesReview           [create]
subjectaccessreviews                           authorization.k8s.io/v1                false        SubjectAccessReview              [create]
horizontalpodautoscalers          hpa          autoscaling/v2                         true         HorizontalPodAutoscaler          [create delete deletecollection get list patch update watch]
cronjobs                          cj           batch/v1                               true         CronJob                          [create delete deletecollection get list patch update watch]
jobs                                           batch/v1                               true         Job                              [create delete deletecollection get list patch update watch]
certificatesigningrequests        csr          certificates.k8s.io/v1                 false        CertificateSigningRequest        [create delete deletecollection get list patch update watch]
leases                                         coordination.k8s.io/v1                 true         Lease                            [create delete deletecollection get list patch update watch]
endpointslices                                 discovery.k8s.io/v1                    true         EndpointSlice                    [create delete deletecollection get list patch update watch]
events                            ev           events.k8s.io/v1                       true         Event                            [create delete deletecollection get list patch update watch]
flowschemas                                    flowcontrol.apiserver.k8s.io/v1beta2   false        FlowSchema                       [create delete deletecollection get list patch update watch]
prioritylevelconfigurations                    flowcontrol.apiserver.k8s.io/v1beta2   false        PriorityLevelConfiguration       [create delete deletecollection get list patch update watch]
ingressclasses                                 networking.k8s.io/v1                   false        IngressClass                     [create delete deletecollection get list patch update watch]
ingresses                         ing          networking.k8s.io/v1                   true         Ingress                          [create delete deletecollection get list patch update watch]
networkpolicies                   netpol       networking.k8s.io/v1                   true         NetworkPolicy                    [create delete deletecollection get list patch update watch]
runtimeclasses                                 node.k8s.io/v1                         false        RuntimeClass                     [create delete deletecollection get list patch update watch]
poddisruptionbudgets              pdb          policy/v1                              true         PodDisruptionBudget              [create delete deletecollection get list patch update watch]
podsecuritypolicies               psp          policy/v1beta1                         false        PodSecurityPolicy                [create delete deletecollection get list patch update watch]
clusterrolebindings                            rbac.authorization.k8s.io/v1           false        ClusterRoleBinding               [create delete deletecollection get list patch update watch]
clusterroles                                   rbac.authorization.k8s.io/v1           false        ClusterRole                      [create delete deletecollection get list patch update watch]
rolebindings                                   rbac.authorization.k8s.io/v1           true         RoleBinding                      [create delete deletecollection get list patch update watch]
roles                                          rbac.authorization.k8s.io/v1           true         Role                             [create delete deletecollection get list patch update watch]
priorityclasses                   pc           scheduling.k8s.io/v1                   false        PriorityClass                    [create delete deletecollection get list patch update watch]
csidrivers                                     storage.k8s.io/v1                      false        CSIDriver                        [create delete deletecollection get list patch update watch]
csinodes                                       storage.k8s.io/v1                      false        CSINode                          [create delete deletecollection get list patch update watch]
csistoragecapacities                           storage.k8s.io/v1beta1                 true         CSIStorageCapacity               [create delete deletecollection get list patch update watch]
storageclasses                    sc           storage.k8s.io/v1                      false        StorageClass                     [create delete deletecollection get list patch update watch]
volumeattachments                              storage.k8s.io/v1                      false        VolumeAttachment                 [create delete deletecollection get list patch update watch]

3. metadata

这个字段是资源对象的"标识"，即元数据，也是我们从 Kubernetes 里找到这个对象的主要依据。包含名称、namespace、标签和注解等信息。metadata中常见的子字段有：

• name: 资源名称，在同一个namespace中必须是唯一的。
• namespace: 命名空间，是对一组资源和对象的抽象集合，对k8s从逻辑上进行划分，实现分层管理，有一定程度上的资源和权限隔离。内置namespace有default，kube-system和kube-public。默认值是default。
• label: 标签数据，可用于在spec中通过selectors进行匹配，达到绑定效果。
• annotation: 注解，一些自定义的辅助信息。

4. spec

spec是指资源内容的规格，即我们资源期望达到的状态，各个资源规格内容不太统一，比如pod的内容包括一些container，volume，nodeSelector等。Deployment的内容包括replicas、selector、template等。

比较全面的具体字段介绍可以参考spec字段常用字段及含义

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