什么是label

Label以key/value键值对的形式附加到任何对象上,如Pod,Service,Node, RC(ReplicationController)/RS(ReplicaSet)等。
一个资源如果需要找到其它关联的资源比如rc匹配pod、deployment匹配rs都是通过selector选择对应的lable达到关联其它对象的目的。

k8s对象的label在资源的metadata定义,例如之前学习过的deplyment定义文件

标签的增删改查

label查询

#查询某一类资源或者指定某个资源查询其label信息
[root@k8s-01 ~]# kubectl get deployment --show-labels
NAME READY UP-TO-DATE AVAILABLE AGE LABELS
nginx-d 3/3 3 3 2d21h app=nginx
wordpress 1/1 1 1 49d app=wordpress,tier=frontend
wordpress-mysql 1/1 1 1 49d app=wordpress,tier=mysql
You have new mail in /var/spool/mail/root
[root@k8s-01 ~]# kubectl get deployment nginx-d --show-labels
NAME READY UP-TO-DATE AVAILABLE AGE LABELS
nginx-d 3/3 3 3 2d21h app=nginx [root@k8s-01 ~]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
nginx-d-659bf7c684-22nc8 1/1 Running 1 2d20h app=nginx,pod-template-hash=659bf7c684
nginx-d-659bf7c684-9l9jk 1/1 Running 1 2d20h app=nginx,pod-template-hash=659bf7c684
nginx-d-659bf7c684-tmtkl 1/1 Running 1 2d20h app=nginx,pod-template-hash=659bf7c684
wordpress-69c467c658-r7c45 1/1 Running 11 49d app=wordpress,pod-template-hash=69c467c658,tier=frontend-pod
wordpress-mysql-6c696cddc9-r6dvx 1/1 Running 15 42d app=wordpress,pod-template-hash=6c696cddc9,tier=mysql-pod
[root@k8s-01 ~]# kubectl get pods nginx-d-659bf7c684-22nc8 --show-labels
NAME READY STATUS RESTARTS AGE LABELS
nginx-d-659bf7c684-22nc8 1/1 Running 1 2d20h app=nginx,pod-template-hash=659bf7c684

label的增加  删除  修改

#指定对象label的添加和删除,添加使用key=value,删除keu-,修改key=value --overwrite
[root@k8s-01 ~]# kubectl get pods nginx-d-659bf7c684-22nc8 --show-labels
NAME READY STATUS RESTARTS AGE LABELS
nginx-d-659bf7c684-22nc8 1/1 Running 1 2d20h app=nginx,pod-template-hash=659bf7c684
[root@k8s-01 ~]#
[root@k8s-01 ~]# kubectl label pods nginx-d-659bf7c684-22nc8 test=label
pod/nginx-d-659bf7c684-22nc8 labeled
[root@k8s-01 ~]# kubectl get pods nginx-d-659bf7c684-22nc8 --show-labels
NAME READY STATUS RESTARTS AGE LABELS
nginx-d-659bf7c684-22nc8 1/1 Running 1 2d20h app=nginx,pod-template-hash=659bf7c684,test=label
[root@k8s-01 ~]# kubectl label pods nginx-d-659bf7c684-22nc8 test-
pod/nginx-d-659bf7c684-22nc8 labeled
[root@k8s-01 ~]# kubectl get pods nginx-d-659bf7c684-22nc8 --show-labels
NAME READY STATUS RESTARTS AGE LABELS
nginx-d-659bf7c684-22nc8 1/1 Running 1 2d20h app=nginx,pod-template-hash=659bf7c684
[root@k8s-01 ~]# kubectl label pods nginx-d-659bf7c684-22nc8 test=label1
pod/nginx-d-659bf7c684-22nc8 labeled
[root@k8s-01 ~]# kubectl get pods nginx-d-659bf7c684-22nc8 --show-labels
NAME READY STATUS RESTARTS AGE LABELS
nginx-d-659bf7c684-22nc8 1/1 Running 1 2d20h app=nginx,pod-template-hash=659bf7c684,test=label1
[root@k8s-01 ~]# kubectl label pods nginx-d-659bf7c684-22nc8 test=label2
error: 'test' already has a value (label1), and --overwrite is false
[root@k8s-01 ~]# kubectl label pods nginx-d-659bf7c684-22nc8 test=label2 --overwrite
pod/nginx-d-659bf7c684-22nc8 labeled
[root@k8s-01 ~]# kubectl get pods nginx-d-659bf7c684-22nc8 --show-labels
NAME READY STATUS RESTARTS AGE LABELS
nginx-d-659bf7c684-22nc8 1/1 Running 1 2d20h app=nginx,pod-template-hash=659bf7c684,test=label2

一般建议k8s对象的label在定义文件中进行定义和修改

nodeselector

nodeselector是pod的专有的选择器,在资源定义文件中可以指定pod在哪些node节点上创建。不配置该参数的话k8s会根据自身算法选择相应的node来部署pod

不配置nodeselector情况下pod的分布,如果有多个node则pod一定分布在多个pod上。

[root@k8s-01 ~]# kubectl get deployment -o wide
NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
nginx-d 3/3 3 3 2d21h nginx nginx:1.18 app=nginx
[root@k8s-01 ~]# kubectl get pod -o wide|grep nginx-d
nginx-d-659bf7c684-22nc8 1/1 Running 1 2d21h 10.244.2.52 k8s-03 <none> <none>
nginx-d-659bf7c684-9l9jk 1/1 Running 1 2d21h 10.244.2.53 k8s-03 <none> <none>
nginx-d-659bf7c684-tmtkl 1/1 Running 1 2d21h 10.244.1.71 k8s-02 <none> <none>

查询环境node信息,给node打上label

[root@k8s-01 ~]# kubectl get nodes --show-labels
NAME STATUS ROLES AGE VERSION LABELS
k8s-01 Ready master 61d v1.15.0 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=k8s-01,kubernetes.io/os=linux,node-role.kubernetes.io/master=
k8s-02 Ready <none> 61d v1.15.0 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=k8s-02,kubernetes.io/os=linux
k8s-03 Ready <none> 61d v1.15.0 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=k8s-03,kubernetes.io/os=linux
[root@k8s-01 ~]# kubectl label nodes k8s-02 selectortest=k8s-02
node/k8s-02 labeled
[root@k8s-01 ~]# kubectl get nodes --show-labels
NAME STATUS ROLES AGE VERSION LABELS
k8s-01 Ready master 61d v1.15.0 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=k8s-01,kubernetes.io/os=linux,node-role.kubernetes.io/master=
k8s-02 Ready <none> 61d v1.15.0 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=k8s-02,kubernetes.io/os=linux,selectortest=k8s-02
k8s-03 Ready <none> 61d v1.15.0 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=k8s-03,kubernetes.io/os=linux

deployment定义文件中pod部分使用nodeselector指定node创建Pod

#pod对象定义中指定nodeSelector后pod调度的效果
[root@k8s-01 ~]# kubectl get deployment
NAME READY UP-TO-DATE AVAILABLE AGE
wordpress 1/1 1 1 49d
wordpress-mysql 1/1 1 1 49d
[root@k8s-01 ~]# kubectl get deployment|grep nginx
[root@k8s-01 ~]# kubectl create -f deployment_demo.yml
deployment.apps/nginx-d created
[root@k8s-01 ~]# kubectl get deployment|grep nginx
nginx-d 0/3 3 0 3s
[root@k8s-01 ~]# kubectl get pods -o wide|grep nginx-d
nginx-d-8668fb97b9-7tw25 1/1 Running 0 43s 10.244.1.75 k8s-02 <none> <none>
nginx-d-8668fb97b9-9hfmb 1/1 Running 0 43s 10.244.1.74 k8s-02 <none> <none>
nginx-d-8668fb97b9-vlzgt 0/1 ContainerCreating 0 43s <none> k8s-02 <none> <none>

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