目录贴：Kubernetes学习系列
1、介绍
之前介绍过DNS的搭建（基于Kubernetes集群部署skyDNS服务），但那个版本的DNS是随着Kubernetes1.2发布出来的，有点原始。本文主要讲解Kubernetes1.4版本中的DNS插件的安装。与1.2版本相比，1.4中的DNS增加了解析Pod（HostName）对应的域名的新功能，且在部署上也有了一些变化。1.2中，需要部署etcd（或使用master上的Etcd）、kube2sky、skydns三个组件；1.4中，DNS组件由kubedns（监控Kubernetes中service变化）、dnsmasq（DNS服务）和一个健康检查容器——healthz组成。
在搭建PetSet（宠物应用）时，系统首先要为PetSet设置一个HeadLess service，即service的ClusterIP显示的设置成none，而对每一个有特定名称的Pet（Named Pod），可以通过其HostName进行寻址访问。这就用到了1.4中的新功能。以下给出具体的搭建过程。
2、修改配置
2.1修改各个node上的kubelet
修改以下红色部分，完成后重启kubelet服务。
[root@k8s-node- ~]# cat /etc/kubernetes/kubelet
###
# kubernetes kubelet (minion) config # The address for the info server to serve on (set to 0.0.0.0 or "" for all interfaces)
KUBELET_ADDRESS="--address=0.0.0.0" # The port for the info server to serve on
# KUBELET_PORT="--port=10250" # You may leave this blank to use the actual hostname
#KUBELET_HOSTNAME="--hostname-override=127.0.0.1"
KUBELET_HOSTNAME="--hostname-override=k8s-node-1" # location of the api-server
KUBELET_API_SERVER="--api-servers=http://k8s-master:8080" # pod infrastructure container
KUBELET_POD_INFRA_CONTAINER="--pod-infra-container-image=registry.access.redhat.com/rhel7/pod-infrastructure:latest" # Add your own!
#KUBELET_ARGS=""
KUBELET_ARGS="--cluster-dns=10.254.10.2 --cluster-domain=cluster.local. --allow-privileged=true"
[root@k8s-node- ~]# systemctl restart kubelet.service
2.2修改APIserver
修改以下红色部分：
[root@k8s-master ~]# cat /etc/kubernetes/apiserver
###
# kubernetes system config
#
# The following values are used to configure the kube-apiserver
# # The address on the local server to listen to.
KUBE_API_ADDRESS="--insecure-bind-address=0.0.0.0" # The port on the local server to listen on.
KUBE_API_PORT="--port=8080" # Port minions listen on
# KUBELET_PORT="--kubelet-port=10250" # Comma separated list of nodes in the etcd cluster
KUBE_ETCD_SERVERS="--etcd-servers=http://etcd:2379" # Address range to use for services
KUBE_SERVICE_ADDRESSES="--service-cluster-ip-range=10.254.0.0/16" # default admission control policies
KUBE_ADMISSION_CONTROL="--admission-control=NamespaceLifecycle,NamespaceExists,LimitRanger,SecurityContextDeny,ResourceQuota" # Add your own!
KUBE_API_ARGS=""
2.3 修改yaml文件
修改以下红色部分：
[root@k8s-master dns14]# cat kube-dns-rc_14.yaml
apiVersion: v1
kind: ReplicationController
metadata:
name: kube-dns-v20
namespace: kube-system
labels:
k8s-app: kube-dns
version: v20
kubernetes.io/cluster-service: "true"
spec:
replicas: 1
selector:
k8s-app: kube-dns
version: v20
template:
metadata:
labels:
k8s-app: kube-dns
version: v20
annotations:
scheduler.alpha.kubernetes.io/critical-pod: ''
scheduler.alpha.kubernetes.io/tolerations: '[{"key":"CriticalAddonsOnly", "operator":"Exists"}]'
spec:
containers:
- name: kubedns
image: gcr.io/google_containers/kubedns-amd64:1.8
imagePullPolicy: IfNotPresent
resources:
# TODO: Set memory limits when we've profiled the container for large
# clusters, then set request = limit to keep this container in
# guaranteed class. Currently, this container falls into the
# "burstable" category so the kubelet doesn't backoff from restarting it.
limits:
memory: 170Mi
requests:
cpu: 100m
memory: 70Mi
livenessProbe:
httpGet:
path: /healthz-kubedns
port:
scheme: HTTP
initialDelaySeconds:
timeoutSeconds:
successThreshold:
failureThreshold:
readinessProbe:
httpGet:
path: /readiness
port:
scheme: HTTP
# we poll on pod startup for the Kubernetes master service and
# only setup the /readiness HTTP server once that's available.
initialDelaySeconds:
timeoutSeconds:
args:
# command = "/kube-dns"
- --domain=cluster.local.
- --dns-port=
- --kube-master-url=http://10.0.251.148:8080
ports:
- containerPort:
name: dns-local
protocol: UDP
- containerPort:
name: dns-tcp-local
protocol: TCP
- name: dnsmasq
image: gcr.io/google_containers/kube-dnsmasq-amd64:1.4.
imagePullPolicy: IfNotPresent
livenessProbe:
httpGet:
path: /healthz-dnsmasq
port:
scheme: HTTP
initialDelaySeconds:
timeoutSeconds:
successThreshold:
failureThreshold:
args:
- --cache-size=
- --no-resolv
- --server=127.0.0.1#
- --log-facility=-
ports:
- containerPort:
name: dns
protocol: UDP
- containerPort:
name: dns-tcp
protocol: TCP
- name: healthz
image: gcr.io/google_containers/exechealthz-amd64:1.2
imagePullPolicy: IfNotPresent
resources:
limits:
memory: 50Mi
requests:
cpu: 10m
# Note that this container shouldn't really need 50Mi of memory. The
# limits are set higher than expected pending investigation on #.
# The extra memory was stolen from the kubedns container to keep the
# net memory requested by the pod constant.
memory: 50Mi
args:
- --cmd=nslookup kubernetes.default.svc.cluster.local. 127.0.0.1 >/dev/null
- --url=/healthz-dnsmasq
- --cmd=nslookup kubernetes.default.svc.cluster.local. 127.0.0.1: >/dev/null
- --url=/healthz-kubedns
- --port=
- --quiet
ports:
- containerPort:
protocol: TCP
dnsPolicy: Default # Don't use cluster DNS.
[root@k8s-master dns14]# cat kube-dns-svc_14.yaml
apiVersion: v1
kind: Service
metadata:
name: kube-dns
namespace: kube-system
labels:
k8s-app: kube-dns
kubernetes.io/cluster-service: "true"
kubernetes.io/name: "KubeDNS"
spec:
selector:
k8s-app: kube-dns
clusterIP: 10.254.10.2
ports:
- name: dns
port:
protocol: UDP
- name: dns-tcp
port:
protocol: TCP
[root@k8s-master dns14]#
2.4 下载镜像
docker pull gcr.io/google_containers/kubedns-amd64:1.8
docker pull gcr.io/google_containers/kube-dnsmasq-amd64:1.4.
docker pull gcr.io/google_containers/exechealthz-amd64:1.2
3、启动
[root@k8s-master dns14]# kubectl create -f kube-dns-rc_14.yaml
replicationcontroller "kube-dns-v20" created
[root@k8s-master dns14]# kubectl create -f kube-dns-svc_14.yaml
service "kube-dns" created
4、验证
注意，以下演示中的web-0与web-1是两个“Named Pod”，是通过创建PetSet创建出来的Pod。详细介绍请参见后续文章。
[root@k8s-master dns14]# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE
frontend-service--xuysd / Running 3h 10.0.82.5 k8s-node-
web- / Running 3h 10.0.28.3 k8s-node-
web- / Running 3h 10.0.82.6 k8s-node-
[root@k8s-master dns14]# kubectl get svc mysql-service
NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
mysql-service 10.254.194.71 <nodes> /TCP 4h
[root@k8s-master dns14]# kubectl exec -ti frontend-service--xuysd /bin/bash
[root@frontend-service--xuysd /]# nslookup web-.nginx
Server: 10.254.10.2
Address: 10.254.10.2# Name: web-.nginx.default.svc.cluster.local
Address: 10.0.28.3 [root@frontend-service--xuysd /]# nslookup web-.nginx
Server: 10.254.10.2
Address: 10.254.10.2# Name: web-.nginx.default.svc.cluster.local
Address: 10.0.82.6 [root@frontend-service--xuysd /]# nslookup web-.nginx.default.svc.cluster.local
Server: 10.254.10.2
Address: 10.254.10.2# Non-authoritative answer:
Name: web-.nginx.default.svc.cluster.local
Address: 10.0.82.6
[root@frontend-service--xuysd /]# nslookup mysql-service
Server: 10.254.10.2
Address: 10.254.10.2# Name: mysql-service.default.svc.cluster.local
Address: 10.254.194.71