编写Kubernetes中编写yaml文件，Pod模板详解
K8s的yaml文件功能十分强大，对于新手来说，想要快速照掌握且灵活运用就显得有些困难。下文将给出Pod模板常用的一些代码及解释，如何快速运用。
Pod中 yaml 的详解
注意：都是以两个空格为递进，而非tab
apiVersion: v1 #必选，版本号，例如v1
kind: Pod #必选，资源类型，例如 Pod,Deployment,ReplicaSet,Replication
metadata: #必选，元数据
name: string #必选，Pod名称
namespace: string #Pod所属的命名空间,默认为"default"
labels: #自定义标签列表
- name: string
spec: #必选，Pod中容器的详细定义
containers: #必选，Pod中容器列表
- name: string #必选，容器名称
image: string #必选，容器的镜像名称
imagePullPolicy: [ Always|Never|IfNotPresent ] #获取镜像的策略
command: [string] #容器的启动命令列表，如不指定，使用打包时使用的启动命令
args: [string] #容器的启动命令参数列表
workingDir: string #容器的工作目录
volumeMounts: #挂载到容器内部的存储卷配置
- name: string #引用pod定义的共享存储卷的名称，需用volumes[]部分定义的的卷名
mountPath: string #存储卷在容器内mount的绝对路径，应少于512字符
readOnly: boolean #是否为只读模式
volumes: #在该pod上定义共享存储卷列表
- name: string #共享存储卷名称 （volumes类型有很多种）
emptyDir: {} #类型为emtyDir的存储卷，与Pod同生命周期的一个临时目录。为空值
hostPath: string #类型为hostPath的存储卷，表示挂载Pod所在宿主机的目录
path: string #Pod所在宿主机的目录，将被用于同期中mount的目录
secret: #类型为secret的存储卷，挂载集群与定义的secret对象到容器内部
scretname: string
items:
- key: string
path: string
configMap: #类型为configMap的存储卷，挂载预定义的configMap对象到容器内部
name: string
items:
- key: string
path: string
ports: #需要暴露的端口库号列表
- name: string #端口的名称
containerPort: int #容器需要监听的端口号
hostPort: int #容器所在主机需要监听的端口号，默认与Container相同
protocol: string #端口协议，支持TCP和UDP，默认TCP
env: #容器运行前需设置的环境变量列表
- name: string #环境变量名称
value: string #环境变量的值
resources: #资源限制和请求的设置
limits: #资源限制的设置
cpu: string #Cpu的限制，单位为core数，将用于docker run --cpu-shares参数
memory: string #内存限制，单位可以为Mib/Gib，将用于docker run --memory参数
requests: #资源请求的设置
cpu: string #Cpu请求，容器启动的初始可用数量
memory: string #内存请求,容器启动的初始可用数量
lifecycle: #生命周期钩子
postStart: #容器启动后立即执行此钩子,如果执行失败,会根据重启策略进行重启
preStop: #容器终止前执行此钩子,无论结果如何,容器都会终止
livenessProbe: #对Pod内各容器健康检查的设置，当探测无响应几次后将自动重启该容器
exec: #对Pod容器内检查方式设置为exec方式
command: [string] #exec方式需要制定的命令或脚本
initialDelaySeconds # 容器启动后等待多少秒执行第一次探测
timeoutSeconds # 探测超时时间。默认1秒，最小1秒
periodSeconds # 执行探测的频率。默认是10秒，最小1秒
failureThreshold # 连续探测失败多少次才被认定为失败。默认是3。最小值是1
successThreshold # 连续探测成功多少次才被认定为成功。默认是1
httpGet: #对Pod内个容器健康检查方法设置为HttpGet，需要制定Path、port
path: string
port: number
host: string
scheme: string
HttpHeaders:
- name: string
value: string
tcpSocket: #对Pod内个容器健康检查方式设置为tcpSocket方式
port: number
initialDelaySeconds: 0 #容器启动完成后首次探测的时间，单位为秒
timeoutSeconds: 0 #对容器健康检查探测等待响应的超时时间，单位秒，默认1秒
periodSeconds: 0 #对容器监控检查的定期探测时间设置，单位秒，默认10秒一次
successThreshold: 0
failureThreshold: 0
securityContext:
privileged: false
restartPolicy: [Always | Never | OnFailure] #Pod的重启策略
nodeName: #设置NodeName表示将该Pod调度到指定到名称的node节点上
nodeSelector: obeject #设置NodeSelector表示将该Pod调度到包含这个label的node上
imagePullSecrets: #Pull镜像时使用的secret名称，以key：secretkey格式指定
- name: string
hostNetwork: false #是否使用主机网络模式，默认为false，如果设置为true，表示使用宿主机网络
在编写yaml的时候，可结合帮助，灵活运用，找到所需的那个代码。
构建pod，ns，rs，rc等等，只需在后面加上即可出现对应模板
kubectl explain pod/ns/rs/rc/networkpolicy/hpa
以pod为例
以pod为例
[root@master ~]# kubectl explain pod
KIND: Pod
VERSION: v1
DEscriptION:
Pod is a collection of containers that can run on a host. This resource is
created by clients and scheduled onto hosts.
FIELDS:
apiVersion
APIVersion defines the versioned schema of this representation of an
object. Servers should convert recognized schemas to the latest internal
value, and may reject unrecognized values. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources
kind
Kind is a string value representing the REST resource this object
represents. Servers may infer this from the endpoint the client submits
requests to. Cannot be updated. In CamelCase. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds
metadata
Standard object's metadata. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
spec
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
status
Most recently observed status of the pod. This data may not be up to date.
Populated by the system. Read-only. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status
逐层往下查看
以pod中的spec为例
[root@master ~]# kubectl explain pod.spec
KIND: Pod
VERSION: v1
RESOURCE: spec
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
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
If specified, the pod's scheduling constraints
automountServiceAccountToken
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
Specifies the DNS parameters of a pod. Parameters specified here will be
merged to the generated DNS configuration based on DNSPolicy.
dnsPolicy
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
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
Use the host's ipc namespace. Optional: Default to false.
hostNetwork
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
Use the host's pid namespace. Optional: Default to false.
hostname
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
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
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
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
PreemptionPolicy is the Policy for preempting pods with lower priority. One
of Never, PreemptLowerPriority. Defaults to PreemptLowerPriority if unset.
This field is alpha-level and is only honored by servers that enable the
NonPreemptingPriority feature.
priority
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
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
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
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
If specified, the pod will be dispatched by specified scheduler. If not
specified, the pod will be dispatched by default scheduler.
securityContext
SecurityContext holds pod-level security attributes and common container
settings. Optional: Defaults to empty. See type description for default
values of each field.
serviceAccount
DeprecatedServiceAccount is a depreciated alias for ServiceAccountName.
Deprecated: Use serviceAccountName instead.
serviceAccountName
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/
shareProcessNamespace
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
If specified, the fully qualified Pod hostname will be
"...svc.". If not
specified, the pod will not have a domainname at all.
terminationGracePeriodSeconds
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 delete immediately. 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. This field is only honored by clusters that enable the
EvenPodsSpread feature. 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
例1
yaml中的实战pod案例，先写个简单的
使用该yaml文件创建Pod要求如下：
其yaml文件如下
[root@master ~]# vim nginx.yaml
apiVersion: v1 #版本号为v1
kind: Pod #资源类型为Pod
metadata: #元数据
name: nginx-pod #Pod名称
spec: #pod容器的详细定义
containers: #容器列表
- name: mynginx #容器名称
image: nginx:latest #容器镜像
imagePullPolicy: IfNotPresent #容器镜像拉取策略
ports: #需要暴露的端口库号列表
- containerPort: 80 #容器需监听的端口号
将其启动，且访问一下，试看是否能够访问到nginx首页
启动编写好的yaml文件
[root@master ~]# kubectl apply -f nginx.yaml
pod/nginx-pod created
查看pod列表
[root@master ~]# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-pod 1/1 Running 0 28s 10.244.1.21 node
访问pod
[root@master ~]# curl 10.244.1.21:80
Welcome to nginx!
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
Welcome to nginx!
If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.
For online documentation and support please refer to
"http://nginx.org/">nginx.org.
Thank you for using nginx.
可见是能够启动成功且可以访问到nginx首页
例2
上点难度吧，写个常用一点的实战案例：
其yaml的编写如下：
[root@master ~]# vim liveness_exec.yaml
apiVersion: v1 #版本号为v1
kind: Pod #资源类型为Pod
metadata: #元数据必写
name: liveness-exec #pod名称为liveness-exec
spec: #容器的详细定义 必写
containers: #容器列表 必写
- name: liveness #容器名称为 liveness
image: busybox:latest #容器所使用的镜像 busybox
args: #容器的启动命令参数列表 必写
- /bin/sh #所要执行的命令
- -c
- touch /tmp/healthy; sleep 60; rm -rf /tmp/healthy; sleep 600
livenessProbe: #Pod内各容器健康检查的设置
exec: #对Pod容器内检查方式设置为exec方式
command: #exec方式需要制定的命令或脚本
- test
- /tmp/healthy
initialDelaySeconds: 5 #容器启动后等待5秒执行第一次探测
periodSeconds: 5 #执行探测的频率每5秒执行一次
[root@master ~]# kubectl apply -f liveness_exec.yaml
pod/liveness-exec created
[root@master ~]# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
liveness-exec 1/1 Running 0 18s 10.244.1.23 node
当pod创建成功以后
进入pod查看是否命令是否有被执行
[root@master ~]# kubectl exec -it liveness-exec /bin/sh
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl kubectl exec [POD] -- [COMMAND] instead.
/ # ls /tmp/
healthy
/ #
可见 healthy 文件创建成功，可等待60秒，再次查看，会发现这个文件已经被删除了，已达到上述的要求。
再例举一个RS的例子：
使用yaml文件创建ReplicaSet 要求如下：
（1）Replicaset名称：nginx；
（2）命名空间：default；
（3）副本数：3；
（4）镜像：nginx。
可借用yaml文件的帮助：
[root@master ~]# kubectl explain rs.spec
KIND: ReplicaSet
VERSION: apps/v1
RESOURCE: spec
DEscriptION:
Spec defines the specification of the desired behavior of the ReplicaSet.
More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status
ReplicaSetSpec is the specification of a ReplicaSet.
FIELDS:
minReadySeconds
Minimum number of seconds for which a newly created pod should be ready
without any of its container crashing, for it to be considered available.
Defaults to 0 (pod will be considered available as soon as it is ready)
replicas
Replicas is the number of desired replicas. This is a pointer to
distinguish between explicit zero and unspecified. Defaults to 1. More
info:
https://kubernetes.io/docs/concepts/workloads/controllers/replicationcontroller/#what-is-a-replicationcontroller
selector -required-
Selector is a label query over pods that should match the replica count.
Label keys and values that must match in order to be controlled by this
replica set. It must match the pod template's labels. More info:
https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#label-selectors
template
Template is the object that describes the pod that will be created if
insufficient replicas are detected. More info:
https://kubernetes.io/docs/concepts/workloads/controllers/replicationcontroller#pod-template
编写rs的yaml文件
[root@master ~]# vim replicaset.yaml
apiVersion: apps/v1
kind: ReplicaSet
metadata:
name: nginx
spec:
replicas: 3
selector:
matchLabels:
nginx: replicaset
template:
metadata:
labels:
nginx: replicaset
spec:
containers:
- name: nginx
image: nginx:latest
将其启动
[root@master ~]# kubectl apply -f replicaset.yaml
replicaset.apps/nginx created
[root@master ~]# kubectl get rs
NAME DESIRED CURRENT READY AGE
nginx 3 3 3 69s
[root@master ~]# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-qjq88 1/1 Running 0 38s 10.244.1.25 node
nginx-xkxvz 1/1 Running 0 38s 10.244.1.24 node
nginx-z8gwx 1/1 Running 0 38s 10.244.0.28 master
访问任意一个IP，都能返回nginx首页内容
Welcome to nginx!
Welcome to nginx!
If you see this page, the nginx web server is successfully installed and working. Further configuration is required.
For online documentation and support please refer to nginx.org.
Thank you for using nginx.
到此over!!
