k8s资源清单

资源清单就是k8s当中用来定义pod的文件，语法格式遵循yaml语法，在yaml当中可以定义控制器类型，元数据，容器端口号等等等....，也可以针对于清单对pod进行删除等操作。

我们可以用kubectl get命令输出一个pod的配置清单，自主式pod清单定义格式如下：

[root@master ~]# kubectl get pods nginx-6799fc88d8-648cn  -o yaml
apiVersion: v1
kind: Pod
metadata:
  annotations:
    cni.projectcalico.org/containerID: 03392441c892b616c7f1bf7ed1a412cdb14a8af20bc0cf67c350d7b87a1872a1
    cni.projectcalico.org/podIP: 10.101.11.3/32
    cni.projectcalico.org/podIPs: 10.101.11.3/32
  creationTimestamp: "2022-05-09T07:57:11Z"
  deletionGracePeriodSeconds: 30
  deletionTimestamp: "2022-05-13T02:35:12Z"
  generateName: nginx-6799fc88d8-
  labels:
    app: nginx
    pod-template-hash: 6799fc88d8
  name: nginx-6799fc88d8-648cn
  namespace: default
  ownerReferences:
  - apiVersion: apps/v1
    blockOwnerDeletion: true
    controller: true
    kind: ReplicaSet
    name: nginx-6799fc88d8
    uid: ab88c364-c138-468d-b0cb-a21bfa23e432
  resourceVersion: "25980"
  uid: 1a471540-a745-4a97-87e1-cc072a56108e
spec:
  containers:
  - image: nginx
    imagePullPolicy: Always
    name: nginx
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access-7cm6p
      readOnly: true
  dnsPolicy: ClusterFirst
  enableServiceLinks: true
  nodeName: node2
  preemptionPolicy: PreemptLowerPriority
  priority: 0
  restartPolicy: Always
  schedulerName: default-scheduler
  securityContext: {}
  serviceAccount: default
  serviceAccountName: default
  terminationGracePeriodSeconds: 30
  tolerations:
  - effect: NoExecute
    key: node.kubernetes.io/not-ready
    operator: Exists
    tolerationSeconds: 300
  - effect: NoExecute
    key: node.kubernetes.io/unreachable
    operator: Exists
    tolerationSeconds: 300
  volumes:
  - name: kube-api-access-7cm6p
    projected:
      defaultMode: 420
      sources:
      - serviceAccountToken:
          expirationSeconds: 3607
          path: token
      - configMap:
          items:
          - key: ca.crt
            path: ca.crt
          name: kube-root-ca.crt
      - downwardAPI:
          items:
          - fieldRef:
              apiVersion: v1
              fieldPath: metadata.namespace
            path: namespace
status:
  conditions:
  - lastProbeTime: null
    lastTransitionTime: "2022-05-09T07:57:11Z"
    status: "True"
    type: Initialized
  - lastProbeTime: null
    lastTransitionTime: "2022-05-13T02:29:26Z"
    status: "False"
    type: Ready
  - lastProbeTime: null
    lastTransitionTime: "2022-05-09T07:58:20Z"
    status: "True"
    type: ContainersReady
  - lastProbeTime: null
    lastTransitionTime: "2022-05-09T07:57:11Z"
    status: "True"
    type: PodScheduled
  containerStatuses:
  - containerID: docker://f5528452cb68da2aabca32f2714ed0f45c59adb5c9b473fcd77850bc07e97881
    image: nginx:latest
    imageID: docker-pullable://nginx@sha256:859ab6768a6f26a79bc42b231664111317d095a4f04e4b6fe79ce37b3d199097
    lastState: {}
    name: nginx
    ready: true
    restartCount: 0
    started: true
    state:
      running:
        startedAt: "2022-05-09T07:58:19Z"
  hostIP: 192.168.248.130
  phase: Running
  podIP: 10.101.11.3
  podIPs:
  - ip: 10.101.11.3
  qosClass: BestEffort
  startTime: "2022-05-09T07:57:11Z"

kubectl get pods nginx-6799fc88d8-648cn -o yaml

资源清单常用字段

1. apiversion

用来指定api的版本，定义的语法格式为group/version,比如我们要定义deployment控制器，那么我们的apiVersion：apps/v1，如果我们要定义自主式pod，那么需要定义apiVersion：v1，如果要获取有哪些apiVersion可以用如下命令

[root@master ~]# kubectl api-versions
admissionregistration.k8s.io/v1
admissionregistration.k8s.io/v1beta1
apiextensions.k8s.io/v1
apiextensions.k8s.io/v1beta1
apiregistration.k8s.io/v1
apiregistration.k8s.io/v1beta1
apps/v1
authentication.k8s.io/v1
authentication.k8s.io/v1beta1
authorization.k8s.io/v1
authorization.k8s.io/v1beta1
autoscaling/v1
autoscaling/v2beta1
autoscaling/v2beta2
batch/v1
batch/v1beta1
certificates.k8s.io/v1
certificates.k8s.io/v1beta1
coordination.k8s.io/v1
coordination.k8s.io/v1beta1
crd.projectcalico.org/v1
discovery.k8s.io/v1
discovery.k8s.io/v1beta1
events.k8s.io/v1
events.k8s.io/v1beta1
extensions/v1beta1
flowcontrol.apiserver.k8s.io/v1beta1
networking.k8s.io/v1
networking.k8s.io/v1beta1
node.k8s.io/v1
node.k8s.io/v1beta1
policy/v1
policy/v1beta1
rbac.authorization.k8s.io/v1
rbac.authorization.k8s.io/v1beta1
scheduling.k8s.io/v1
scheduling.k8s.io/v1beta1
storage.k8s.io/v1
storage.k8s.io/v1beta1
v1

kubectl api-versions

2.kind

kind字段主要用于定义控制器类型,指的是yml文件定义的资源类型和角色，比如：我们想定义一个自助式pod，那么我们就应该定义kind：Pod，如果我们要定义一个deployment控制器管理的pod，那么我们就应该定义kind：Deployment

3.metadate  元数据

对于metadata字段为元数据，我们已经知道k8s是通过标签选择器的方式管理pod，因此，在metadata当中最重要的就是标签，我们可以在metadata当中定义名称空间，标签等，我们如果想查看metadata下可以定义哪些元数据可以使用kubectl explain pod.metadata命令来查看

labels：标签选择器，labels的值决定service控制器关联pod的重要选项

name：这里是自主式pod名称，如果是控制器pod，这里是控制器名称

namespace：名称空间，默认为default名称空间

annotations：资源注解，这里跟labels很像，都是键值对，但是不同点是，不能用于挑选资源对象，仅用于“元数据”

4.spec字段

spec字段用来定义期望容器达到的状态，在spec字段当中可以定义多个容器，容器的名称，容器的镜像，拖取容器镜像的方式，暴露的端口号，存储卷，容器个数等，也就是说真正定义pod是在spec字段当中定义的。

spec:
  containers:                                                         容器列表定义
  - image: nginx                                                      用到的镜像名称
    imagePullPolicy: Always                                           定义镜像的拉取策略，一共是有三种方式 1、Always 每次都尝试重新拉取镜像 2、Never  表示只使用本地镜像 3、IfNotPresent 如果有本地镜像就使用本地镜像，没有就在线拉取 默认Always
    name: nginx                                                       定义容器的名字
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:                                                     容器内部的存储卷配置
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount        指定可以被容器挂载存储卷的路径
      name: kube-api-access-7cm6p                                     指定可以被容器挂载的存储卷的名称
      readOnly: true                                                  设置存储卷的的读写模式，true或者false，默认是true 读写模式
  dnsPolicy: ClusterFirst
  enableServiceLinks: true
  nodeName: node2
  preemptionPolicy: PreemptLowerPriority
  priority: 0
  restartPolicy: Always                                               定义pod的重启策略，一般有三种模式1、 Always pod一旦终止运行，无论容器是怎样退出的kubelet都将重启它 2、OnFailure 只有pod在非0退出码退出时，kubelet才将容器重启 3、Never 在pod终止时不重启。
  schedulerName: default-scheduler
  securityContext: {}
  serviceAccount: default
  serviceAccountName: default
  terminationGracePeriodSeconds: 30
  tolerations:
  - effect: NoExecute
    key: node.kubernetes.io/not-ready
    operator: Exists
    tolerationSeconds: 300
  - effect: NoExecute
    key: node.kubernetes.io/unreachable
    operator: Exists
    tolerationSeconds: 300
  volumes:
  - name: kube-api-access-7cm6p
    projected:
      defaultMode: 420
      sources:
      - serviceAccountToken:
          expirationSeconds: 3607
          path: token
      - configMap:
          items:
          - key: ca.crt
            path: ca.crt
          name: kube-root-ca.crt
      - downwardAPI:
          items:
          - fieldRef:
              apiVersion: v1
              fieldPath: metadata.namespace
            path: namespace

查看spec详细用法命令

kubectl explain pod.spec

root@master ~]# kubectl explain pod.spec
KIND:     Pod
VERSION:  v1

RESOURCE: spec <Object>

DESCRIPTION:
     Specification of the desired behavior of the pod. More info:
     https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status

     PodSpec is a description of a pod.

FIELDS:
   activeDeadlineSeconds        <integer>
     Optional duration in seconds the pod may be active on the node relative to
     StartTime before the system will actively try to mark it failed and kill
     associated containers. Value must be a positive integer.

   affinity     <Object>
     If specified, the pod's scheduling constraints

   automountServiceAccountToken <boolean>
     AutomountServiceAccountToken indicates whether a service account token
     should be automatically mounted.

   containers   <[]Object> -required-
     List of containers belonging to the pod. Containers cannot currently be
     added or removed. There must be at least one container in a Pod. Cannot be
     updated.

   dnsConfig    <Object>
     Specifies the DNS parameters of a pod. Parameters specified here will be
     merged to the generated DNS configuration based on DNSPolicy.

   dnsPolicy    <string>
     Set DNS policy for the pod. Defaults to "ClusterFirst". Valid values are
     'ClusterFirstWithHostNet', 'ClusterFirst', 'Default' or 'None'. DNS
     parameters given in DNSConfig will be merged with the policy selected with
     DNSPolicy. To have DNS options set along with hostNetwork, you have to
     specify DNS policy explicitly to 'ClusterFirstWithHostNet'.

   enableServiceLinks   <boolean>
     EnableServiceLinks indicates whether information about services should be
     injected into pod's environment variables, matching the syntax of Docker
     links. Optional: Defaults to true.

   ephemeralContainers  <[]Object>
     List of ephemeral containers run in this pod. Ephemeral containers may be
     run in an existing pod to perform user-initiated actions such as debugging.
     This list cannot be specified when creating a pod, and it cannot be
     modified by updating the pod spec. In order to add an ephemeral container
     to an existing pod, use the pod's ephemeralcontainers subresource. This
     field is alpha-level and is only honored by servers that enable the
     EphemeralContainers feature.

   hostAliases  <[]Object>
     HostAliases is an optional list of hosts and IPs that will be injected into
     the pod's hosts file if specified. This is only valid for non-hostNetwork
     pods.

   hostIPC      <boolean>
     Use the host's ipc namespace. Optional: Default to false.

   hostNetwork  <boolean>
     Host networking requested for this pod. Use the host's network namespace.
     If this option is set, the ports that will be used must be specified.
     Default to false.

   hostPID      <boolean>
     Use the host's pid namespace. Optional: Default to false.

   hostname     <string>
     Specifies the hostname of the Pod If not specified, the pod's hostname will
     be set to a system-defined value.

   imagePullSecrets     <[]Object>
     ImagePullSecrets is an optional list of references to secrets in the same
     namespace to use for pulling any of the images used by this PodSpec. If
     specified, these secrets will be passed to individual puller
     implementations for them to use. For example, in the case of docker, only
     DockerConfig type secrets are honored. More info:
     https://kubernetes.io/docs/concepts/containers/images#specifying-imagepullsecrets-on-a-pod

   initContainers       <[]Object>
     List of initialization containers belonging to the pod. Init containers are
     executed in order prior to containers being started. If any init container
     fails, the pod is considered to have failed and is handled according to its
     restartPolicy. The name for an init container or normal container must be
     unique among all containers. Init containers may not have Lifecycle
     actions, Readiness probes, Liveness probes, or Startup probes. The
     resourceRequirements of an init container are taken into account during
     scheduling by finding the highest request/limit for each resource type, and
     then using the max of of that value or the sum of the normal containers.
     Limits are applied to init containers in a similar fashion. Init containers
     cannot currently be added or removed. Cannot be updated. More info:
     https://kubernetes.io/docs/concepts/workloads/pods/init-containers/

   nodeName     <string>
     NodeName is a request to schedule this pod onto a specific node. If it is
     non-empty, the scheduler simply schedules this pod onto that node, assuming
     that it fits resource requirements.

   nodeSelector <map[string]string>
     NodeSelector is a selector which must be true for the pod to fit on a node.
     Selector which must match a node's labels for the pod to be scheduled on
     that node. More info:
     https://kubernetes.io/docs/concepts/configuration/assign-pod-node/

   overhead     <map[string]string>
     Overhead represents the resource overhead associated with running a pod for
     a given RuntimeClass. This field will be autopopulated at admission time by
     the RuntimeClass admission controller. If the RuntimeClass admission
     controller is enabled, overhead must not be set in Pod create requests. The
     RuntimeClass admission controller will reject Pod create requests which
     have the overhead already set. If RuntimeClass is configured and selected
     in the PodSpec, Overhead will be set to the value defined in the
     corresponding RuntimeClass, otherwise it will remain unset and treated as
     zero. More info:
     https://git.k8s.io/enhancements/keps/sig-node/20190226-pod-overhead.md This
     field is alpha-level as of Kubernetes v1.16, and is only honored by servers
     that enable the PodOverhead feature.

   preemptionPolicy     <string>
     PreemptionPolicy is the Policy for preempting pods with lower priority. One
     of Never, PreemptLowerPriority. Defaults to PreemptLowerPriority if unset.
     This field is beta-level, gated by the NonPreemptingPriority feature-gate.

   priority     <integer>
     The priority value. Various system components use this field to find the
     priority of the pod. When Priority Admission Controller is enabled, it
     prevents users from setting this field. The admission controller populates
     this field from PriorityClassName. The higher the value, the higher the
     priority.

   priorityClassName    <string>
     If specified, indicates the pod's priority. "system-node-critical" and
     "system-cluster-critical" are two special keywords which indicate the
     highest priorities with the former being the highest priority. Any other
     name must be defined by creating a PriorityClass object with that name. If
     not specified, the pod priority will be default or zero if there is no
     default.

   readinessGates       <[]Object>
     If specified, all readiness gates will be evaluated for pod readiness. A
     pod is ready when all its containers are ready AND all conditions specified
     in the readiness gates have status equal to "True" More info:
     https://git.k8s.io/enhancements/keps/sig-network/0007-pod-ready%2B%2B.md

   restartPolicy        <string>
     Restart policy for all containers within the pod. One of Always, OnFailure,
     Never. Default to Always. More info:
     https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle/#restart-policy

   runtimeClassName     <string>
     RuntimeClassName refers to a RuntimeClass object in the node.k8s.io group,
     which should be used to run this pod. If no RuntimeClass resource matches
     the named class, the pod will not be run. If unset or empty, the "legacy"
     RuntimeClass will be used, which is an implicit class with an empty
     definition that uses the default runtime handler. More info:
     https://git.k8s.io/enhancements/keps/sig-node/runtime-class.md This is a
     beta feature as of Kubernetes v1.14.

   schedulerName        <string>
     If specified, the pod will be dispatched by specified scheduler. If not
     specified, the pod will be dispatched by default scheduler.

   securityContext      <Object>
     SecurityContext holds pod-level security attributes and common container
     settings. Optional: Defaults to empty. See type description for default
     values of each field.

   serviceAccount       <string>
     DeprecatedServiceAccount is a depreciated alias for ServiceAccountName.
     Deprecated: Use serviceAccountName instead.

   serviceAccountName   <string>
     ServiceAccountName is the name of the ServiceAccount to use to run this
     pod. More info:
     https://kubernetes.io/docs/tasks/configure-pod-container/configure-service-account/

   setHostnameAsFQDN    <boolean>
     If true the pod's hostname will be configured as the pod's FQDN, rather
     than the leaf name (the default). In Linux containers, this means setting
     the FQDN in the hostname field of the kernel (the nodename field of struct
     utsname). In Windows containers, this means setting the registry value of
     hostname for the registry key
     HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters to
     FQDN. If a pod does not have FQDN, this has no effect. Default to false.

   shareProcessNamespace        <boolean>
     Share a single process namespace between all of the containers in a pod.
     When this is set containers will be able to view and signal processes from
     other containers in the same pod, and the first process in each container
     will not be assigned PID 1. HostPID and ShareProcessNamespace cannot both
     be set. Optional: Default to false.

   subdomain    <string>
     If specified, the fully qualified Pod hostname will be
     "<hostname>.<subdomain>.<pod namespace>.svc.<cluster domain>". If not
     specified, the pod will not have a domainname at all.

   terminationGracePeriodSeconds        <integer>
     Optional duration in seconds the pod needs to terminate gracefully. May be
     decreased in delete request. Value must be non-negative integer. The value
     zero indicates stop immediately via the kill signal (no opportunity to shut
     down). If this value is nil, the default grace period will be used instead.
     The grace period is the duration in seconds after the processes running in
     the pod are sent a termination signal and the time when the processes are
     forcibly halted with a kill signal. Set this value longer than the expected
     cleanup time for your process. Defaults to 30 seconds.

   tolerations  <[]Object>
     If specified, the pod's tolerations.

   topologySpreadConstraints    <[]Object>
     TopologySpreadConstraints describes how a group of pods ought to spread
     across topology domains. Scheduler will schedule pods in a way which abides
     by the constraints. All topologySpreadConstraints are ANDed.

   volumes      <[]Object>
     List of volumes that can be mounted by containers belonging to the pod.
     More info: https://kubernetes.io/docs/concepts/storage/volumes

kubectl explain pod.spec