前言:
kubernetes把所有的插件统一放在了.../cluster/addons下了
从早期的发布的版本看到,2015年1月, kubernetes 0.8.x系列版本中.../cluster/addons目录被加入进来.addons被用来放置独立出来的插件,
addons目录中最早被放入的是dns和cluster-monitoring(可以看kubernetes 0.8.0版本)
0.8.0版本中名称还是skydns.
E:\k8s源码\kubernetes-0.8.0\cluster\addons\dns\README.md
## How does it work? SkyDNS depends on etcd for what to serve, but it doesn't really need all of what etcd offers in the way we use it. For simplicty, we run etcd and SkyDNS together in a pod, and we do not try to link etcd instances across replicas. A helper container called `kube2sky` also runs in the pod and acts a bridge between Kubernetes and SkyDNS. It finds the Kubernetes master through the `kubernetes-ro` service, it pulls service info from the master, and it writes that to etcd for SkyDNS to find.
当时用的skydns,该项目地址为: https://github.com/skynetservices/skydns
其中的makefile文件如下:
all: skydns
skydns:
CGO_ENABLED=0 go build -a --ldflags '-w' github.com/skynetservices/skydns
container: skydns
docker build -t kubernetes/skydns .
push:
docker push kubernetes/skydns
clean:
rm -f skydns
//当时是把skydns制作成docker容器来运行的,skydns依赖etcd运行
//所以早期的dns服务是由kube2sky、skyDNS、etcd组成,都是按照docker容器部署的方式
E:\k8s源码\kubernetes-0.8.0\kubernetes-0.8.0\cluster\addons\dns\kube2sky\Dockerfile
E:\k8s源码\kubernetes-0.8.0\kubernetes-0.8.0\cluster\addons\dns\skydns\Dockerfile
详细可查看E:\k8s源码\kubernetes-0.8.0\kubernetes-0.8.0\cluster\addons\dns\README.md
经历几个版本都在沿用skydns，kubernetes 1.3.0 版本中 dns在addons下是消失.
1.4.0版本中dns再次出现时，kube-dns出现这个名称(skydns正式改名). 但是文件名称还是为skydns
1.6.0版本开始变成不在有skydns,全部为kube-dns
E:\k8s源码\kubernetes-1.6.0\kubernetes-1.6.0\cluster\addons\dns
1.6版本的kube-dns变化很大，开始由多个pod一起提供dns服务
kube-dns主要由三个容器组成，分别是 dnsmasq, kube-dns, sidecar(文件内的三个文件就是组成部分) //E:\k8s源码\kubernetes-1.6.0\kubernetes-1.6.0\cluster\addons\dns\kubedns-cm.yaml apiVersion: v1 kind: ConfigMap metadata: name: kube-dns namespace: kube-system labels: addonmanager.kubernetes.io/mode: EnsureExists //E:\k8s源码\kubernetes-1.6.0\kubernetes-1.6.0\cluster\addons\dns\kubedns-controller.yaml.base apiVersion: extensions/v1beta1 kind: Deployment metadata: name: kube-dns namespace: kube-system labels: k8s-app: kube-dns kubernetes.io/cluster-service: "true" addonmanager.kubernetes.io/mode: Reconcile spec: # replicas: not specified here: # 1. In order to make Addon Manager do not reconcile this replicas parameter. # 2. Default is 1. # 3. Will be tuned in real time if DNS horizontal auto-scaling is turned on. strategy: rollingUpdate: maxSurge: 10% maxUnavailable: 0 selector: matchLabels: k8s-app: kube-dns template: metadata: labels: k8s-app: kube-dns annotations: scheduler.alpha.kubernetes.io/critical-pod: '' spec: tolerations: - key: "CriticalAddonsOnly" operator: "Exists" volumes: - name: kube-dns-config configMap: name: kube-dns optional: true containers: - name: kubedns image: gcr.io/google_containers/k8s-dns-kube-dns-amd64:1.14.1 //下载tar包来使用. 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: /healthcheck/kubedns port: 10054 scheme: HTTP initialDelaySeconds: 60 timeoutSeconds: 5 successThreshold: 1 failureThreshold: 5 readinessProbe: httpGet: path: /readiness port: 8081 scheme: HTTP # we poll on pod startup for the Kubernetes master service and # only setup the /readiness HTTP server once that's available. initialDelaySeconds: 3 timeoutSeconds: 5 args: - --domain=__PILLAR__DNS__DOMAIN__. - --dns-port=10053 - --config-dir=/kube-dns-config - --v=2 __PILLAR__FEDERATIONS__DOMAIN__MAP__ env: - name: PROMETHEUS_PORT value: "10055" ports: - containerPort: 10053 name: dns-local protocol: UDP - containerPort: 10053 name: dns-tcp-local protocol: TCP - containerPort: 10055 name: metrics protocol: TCP volumeMounts: - name: kube-dns-config mountPath: /kube-dns-config - name: dnsmasq image: gcr.io/google_containers/k8s-dns-dnsmasq-nanny-amd64:1.14.1 livenessProbe: httpGet: path: /healthcheck/dnsmasq port: 10054 scheme: HTTP initialDelaySeconds: 60 timeoutSeconds: 5 successThreshold: 1 failureThreshold: 5 args: - -v=2 - -logtostderr - -configDir=/etc/k8s/dns/dnsmasq-nanny - -restartDnsmasq=true - -- - -k - --cache-size=1000 - --log-facility=- - --server=/__PILLAR__DNS__DOMAIN__/127.0.0.1#10053 - --server=/in-addr.arpa/127.0.0.1#10053 - --server=/ip6.arpa/127.0.0.1#10053 ports: - containerPort: 53 name: dns protocol: UDP - containerPort: 53 name: dns-tcp protocol: TCP # see: https://github.com/kubernetes/kubernetes/issues/29055 for details resources: requests: cpu: 150m memory: 20Mi volumeMounts: - name: kube-dns-config mountPath: /etc/k8s/dns/dnsmasq-nanny - name: sidecar image: gcr.io/google_containers/k8s-dns-sidecar-amd64:1.14.1 livenessProbe: httpGet: path: /metrics port: 10054 scheme: HTTP initialDelaySeconds: 60 timeoutSeconds: 5 successThreshold: 1 failureThreshold: 5 args: - --v=2 - --logtostderr - --probe=kubedns,127.0.0.1:10053,kubernetes.default.svc.__PILLAR__DNS__DOMAIN__,5,A - --probe=dnsmasq,127.0.0.1:53,kubernetes.default.svc.__PILLAR__DNS__DOMAIN__,5,A ports: - containerPort: 10054 name: metrics protocol: TCP resources: requests: memory: 20Mi cpu: 10m dnsPolicy: Default # Don't use cluster DNS. serviceAccountName: kube-dns //E:\k8s源码\kubernetes-1.6.0\kubernetes-1.6.0\cluster\addons\dns\kubedns-svc.yaml.base apiVersion: v1 kind: Service metadata: name: kube-dns namespace: kube-system labels: k8s-app: kube-dns kubernetes.io/cluster-service: "true" addonmanager.kubernetes.io/mode: Reconcile kubernetes.io/name: "KubeDNS" spec: selector: k8s-app: kube-dns clusterIP: __PILLAR__DNS__SERVER__ ports: - name: dns port: 53 protocol: UDP - name: dns-tcp port: 53 protocol: TCP //E:\k8s源码\kubernetes-1.6.0\kubernetes-1.6.0\cluster\addons\dns\kubedns-sa.yaml apiVersion: v1 kind: ServiceAccount metadata: name: kube-dns labels: kubernetes.io/cluster-service: "true" addonmanager.kubernetes.io/mode: Reconcile
1.9版本开始正式加入coredns支持,出现了kube-dns与coredns共存的状况
E:\k8s源码\kubernetes-1.10.13\kubernetes-1.10.13\cluster(sh和yaml)\addons\dns\README.md
//这段说明也比较有意思，说明很明确是以pod和service方式来提供dns服务
`kube-dns` schedules DNS Pods and Service on the cluster, other pods in cluster can use the DNS Service’s IP to resolve DNS names. * [Administrators guide](http://kubernetes.io/docs/admin/dns/) * [Code repository](http://www.github.com/kubernetes/dns) //独立子项目
E:\k8s源码\kubernetes-1.10.13\kubernetes-1.10.13\cluster\addons\dns\coredns.yaml.base
//镜像用的是 k8s.gcr.io/coredns:1.0.6
https://github.com/coredns/coredns(这里由于是github不是很稳定，访问有时候会无法显示)
官方: https://coredns.io/ 
https://github.com/coredns/coredns
|
下面解释什么是coredns(早期的kubernetes是集成的自己的kube-dns) CoreDNS is a DNS server that chains plugins CoreDNS is a DNS server/forwarder, written in Go, that chains plugins. Each plugin performs a (DNS) function. CoreDNS is a Cloud Native Computing Foundation graduated project. CoreDNS is a fast and flexible DNS server. The key word here is flexible: with CoreDNS you are able to do what you want with your DNS data by utilizing plugins. If some functionality is not provided out of the box you can add it by writing a plugin. CoreDNS can listen for DNS requests coming in over UDP/TCP (go'old DNS), TLS (RFC 7858), also called DoT, DNS over HTTP/2 - DoH - (RFC 8484) and gRPC (not a standard). Currently CoreDNS is able to:
And more. Each of the plugins is documented. See coredns.io/plugins for all in-tree plugins, and coredns.io/explugins for all out-of-tree plugins.
coredns作为Kubernetes插件的比较详细的工作机制,请参看 https://coredns.io/plugins/kubernetes/ coredns本身也提供了自身的插件扩展机制，方便二次开发coredns本身的插件项目列表: https://coredns.io/plugins/ (coredns本身也是一个小生态系统) |
一 coredns二进制程序
1.安装可以使用二进制下载地址: https://github.com/coredns/coredns/releases 例如: https://github.com/coredns/coredns/releases/download/v1.8.5/coredns_1.8.5_linux_arm64.tgz
2.安装可以编译
Compilation from Source To compile CoreDNS, we assume you have a working Go setup. See various tutorials if you don’t have that already configured. First, make sure your golang version is 1.17 or higher as go mod support and other api is needed. See here for go mod details.
Then, check out the project and run make to compile the binary:
[root@k2 src]# git clone https://github.com/coredns/coredns -b v1.8.5 //下载指定版本,这里是coredns 1.8.5版本
或
[root@k2 src]# git clone https://github.com/coredns/coredns //最新
[root@k2 src]# cd coredns
[root@k2 src]# make
二 配置(CoreDNS 是以 Pod 的形式运行) 1. coredns.yaml (kubernetes 1.10.13版本)
[root@k2 dns]# cat coredns.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
name: coredns
namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
labels:
kubernetes.io/bootstrapping: rbac-defaults
name: system:coredns
rules:
- apiGroups:
- ""
resources:
- endpoints
- services
- pods
- namespaces
verbs:
- list
- watch
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
annotations:
rbac.authorization.kubernetes.io/autoupdate: "true"
labels:
kubernetes.io/bootstrapping: rbac-defaults
name: system:coredns
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: system:coredns
subjects:
- kind: ServiceAccount
name: coredns
namespace: kube-system
---
apiVersion: v1
kind: ConfigMap
metadata:
name: coredns
namespace: kube-system
data:
Corefile: |
.:53 {
errors
health
kubernetes cluster.local REVERSE_CIDRS {
pods insecure
upstream
fallthrough in-addr.arpa ip6.arpa
}
prometheus :9153
proxy . /etc/resolv.conf
cache 30
}
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: coredns
namespace: kube-system
labels:
k8s-app: kube-dns
kubernetes.io/name: "CoreDNS"
spec:
replicas: 2
strategy:
type: RollingUpdate
rollingUpdate:
maxUnavailable: 1
selector:
matchLabels:
k8s-app: kube-dns
template:
metadata:
labels:
k8s-app: kube-dns
spec:
serviceAccountName: coredns
tolerations:
- key: "CriticalAddonsOnly"
operator: "Exists"
containers:
- name: coredns
image: coredns/coredns:1.1.1 //镜像的名称和版本
imagePullPolicy: IfNotPresent
args: [ "-conf", "/etc/coredns/Corefile" ]
volumeMounts:
- name: config-volume
mountPath: /etc/coredns
ports:
- containerPort: 53
name: dns
protocol: UDP
- containerPort: 53
name: dns-tcp
protocol: TCP
- containerPort: 9153
name: metrics
protocol: TCP
livenessProbe:
httpGet:
path: /health
port: 8080
scheme: HTTP
initialDelaySeconds: 60
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 5
dnsPolicy: Default
volumes:
- name: config-volume
configMap:
name: coredns
items:
- key: Corefile
path: Corefile
---
apiVersion: v1
kind: Service
metadata:
name: kube-dns
namespace: kube-system
annotations:
prometheus.io/scrape: "true"
labels:
k8s-app: kube-dns
kubernetes.io/cluster-service: "true"
kubernetes.io/name: "CoreDNS"
spec:
selector:
k8s-app: kube-dns
clusterIP: 172.17.0.2
ports:
- name: dns
port: 53
protocol: UDP
- name: dns-tcp
port: 53
protocol: TCP
2.查下tar包 (下载coredns的tar包，docker load -i ...导入)
[root@k2 dns]# docker images | grep corecoredns/coredns 1.1.1 68af89c45ded 4 years ago 46.3MB
参考:
https://github.com/coredns/deployment/tree/master/kubernetes
写个脚本deploy.sh,执行下，把相关信息写入 coredns.yaml
1.coredns.yaml.sed
[root@k2 dns]# vi coredns.yaml.sed
apiVersion: v1
kind: ServiceAccount
metadata:
name: coredns
namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
labels:
kubernetes.io/bootstrapping: rbac-defaults
name: system:coredns
rules:
- apiGroups:
- ""
resources:
- endpoints
- services
- pods
- namespaces
verbs:
- list
- watch
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
annotations:
rbac.authorization.kubernetes.io/autoupdate: "true"
labels:
kubernetes.io/bootstrapping: rbac-defaults
name: system:coredns
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: system:coredns
subjects:
- kind: ServiceAccount
name: coredns
namespace: kube-system
---
apiVersion: v1
kind: ConfigMap
metadata:
name: coredns
namespace: kube-system
data:
Corefile: |
.:53 {
errors
health
kubernetes CLUSTER_DOMAIN REVERSE_CIDRS {
pods insecure
upstream
fallthrough in-addr.arpa ip6.arpa
}
prometheus :9153
proxy . /etc/resolv.conf
cache 30
}
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: coredns
namespace: kube-system
labels:
k8s-app: kube-dns
kubernetes.io/name: "CoreDNS"
spec:
replicas: 2
strategy:
type: RollingUpdate
rollingUpdate:
maxUnavailable: 1
selector:
matchLabels:
k8s-app: kube-dns
template:
metadata:
labels:
k8s-app: kube-dns
spec:
serviceAccountName: coredns
tolerations:
- key: "CriticalAddonsOnly"
operator: "Exists"
containers:
- name: coredns
image: coredns/coredns:1.8.7
imagePullPolicy: IfNotPresent //本地包,从docker images镜像中加载
args: [ "-conf", "/etc/coredns/Corefile" ]
volumeMounts:
- name: config-volume
mountPath: /etc/coredns
ports:
- containerPort: 53
name: dns
protocol: UDP
- containerPort: 53
name: dns-tcp
protocol: TCP
- containerPort: 9153
name: metrics
protocol: TCP
livenessProbe:
httpGet:
path: /health
port: 8080
scheme: HTTP
initialDelaySeconds: 60
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 5
dnsPolicy: Default
volumes:
- name: config-volume
configMap:
name: coredns
items:
- key: Corefile
path: Corefile
---
apiVersion: v1
kind: Service
metadata:
name: kube-dns
namespace: kube-system
annotations:
prometheus.io/scrape: "true"
labels:
k8s-app: kube-dns
kubernetes.io/cluster-service: "true"
kubernetes.io/name: "CoreDNS"
spec:
selector:
k8s-app: kube-dns
clusterIP: CLUSTER_DNS_IP
ports:
- name: dns
port: 53
protocol: UDP
- name: dns-tcp
port: 53
protocol: TCP
拉取镜像
[root@k2 tarcoredns]# docker pull coredns/coredns
[root@k2 tarcoredns]# docker images | grep core coredns/coredns latest 51e6b70358b2 12 days ago 48.7MB
//如果拉取特定版本的镜像可以，查看下版本https://github.com/coredns/coredns/releases/
[root@k2 tarcoredns]# docker pull coredns/coredns:1.8.7
1.8.7: Pulling from coredns/coredns
d92bdee79785: Already exists
224e0372b0f6: Pull complete
Digest: sha256:58508c172b14716350dc5185baefd78265a703514281d309d1d54aa1b721ad68
Status: Downloaded newer image for coredns/coredns:1.8.7
//然后你在对他进行重新命名标签. 或者也可以导出镜像，这样就有自己的该版本的tar包了.
[root@k2 tarcoredns]# docker images | grep core coredns/coredns 1.8.7 51e6b70358b2 12 days ago 48.7MB
2.deploy.sh
[root@k2 dns]# vi deploy.sh
#!/bin/bash
# Deploys CoreDNS to a cluster currently running Kube-DNS.
SERVICE_CIDR=${1:-172.17.0.0/16}
POD_CIDR=${2:-172.17.0.0/16}
CLUSTER_DNS_IP=${3:-172.17.0.2}
CLUSTER_DOMAIN=${4:-cluster.local}
YAML_TEMPLATE=${5:-`pwd`/coredns.yaml.sed}
sed -e s/CLUSTER_DNS_IP/$CLUSTER_DNS_IP/g -e s/CLUSTER_DOMAIN/$CLUSTER_DOMAIN/g -e s?SERVICE_CIDR?$SERVICE_CIDR?g -e s?POD_CIDR?$POD_CIDR?g $YAML_TEMPLATE > coredns.yaml
参考: https://github.com/coredns/deployment/blob/master/kubernetes/deploy.sh
#!/bin/bash
# Deploys CoreDNS to a cluster currently running Kube-DNS.
show_help () {
cat << USAGE
usage: $0 [ -r REVERSE-CIDR ] [ -i DNS-IP ] [ -d CLUSTER-DOMAIN ] [ -t YAML-TEMPLATE ]
-r : Define a reverse zone for the given CIDR. You may specify this option more
than once to add multiple reverse zones. If no reverse CIDRs are defined,
then the default is to handle all reverse zones (i.e. in-addr.arpa and ip6.arpa)
-i : Specify the cluster DNS IP address. If not specified, the IP address of
the existing "kube-dns" service is used, if present.
-s : Skips the translation of kube-dns configmap to the corresponding CoreDNS Corefile configuration.
USAGE
exit 0
}
# Simple Defaults
DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null && pwd )"
CLUSTER_DOMAIN=cluster.local
YAML_TEMPLATE="$DIR/coredns.yaml.sed"
STUBDOMAINS=""
UPSTREAM=\\/etc\\/resolv\.conf
# Translates the kube-dns ConfigMap to equivalent CoreDNS Configuration.
function translate-kube-dns-configmap {
kube-dns-upstreamnameserver-to-coredns
kube-dns-stubdomains-to-coredns
}
function kube-dns-upstreamnameserver-to-coredns {
up=$(kubectl -n kube-system get configmap kube-dns -ojsonpath='{.data.upstreamNameservers}' 2> /dev/null | tr -d '[",]')
if [[ ! -z ${up} ]]; then
UPSTREAM=${up}
fi
}
function kube-dns-stubdomains-to-coredns {
STUBDOMAIN_TEMPLATE='
SD_DOMAIN:53 {
errors
cache 30
loop
forward . SD_DESTINATION {
max_concurrent 1000
}
}'
function dequote {
str=${1#\"} # delete leading quote
str=${str%\"} # delete trailing quote
echo ${str}
}
function parse_stub_domains() {
sd=$1
# get keys - each key is a domain
sd_keys=$(echo -n $sd | jq keys[])
# For each domain ...
for dom in $sd_keys; do
dst=$(echo -n $sd | jq '.['$dom'][0]') # get the destination
dom=$(dequote $dom)
dst=$(dequote $dst)
sd_stanza=${STUBDOMAIN_TEMPLATE/SD_DOMAIN/$dom} # replace SD_DOMAIN
sd_stanza=${sd_stanza/SD_DESTINATION/$dst} # replace SD_DESTINATION
echo "$sd_stanza"
done
}
sd=$(kubectl -n kube-system get configmap kube-dns -ojsonpath='{.data.stubDomains}' 2> /dev/null)
STUBDOMAINS=$(parse_stub_domains "$sd")
}
# Get Opts
while getopts "hsr:i:d:t:k:" opt; do
case "$opt" in
h) show_help
;;
s) SKIP=1
;;
r) REVERSE_CIDRS="$REVERSE_CIDRS $OPTARG"
;;
i) CLUSTER_DNS_IP=$OPTARG
;;
d) CLUSTER_DOMAIN=$OPTARG
;;
t) YAML_TEMPLATE=$OPTARG
;;
esac
done
# Conditional Defaults
if [[ -z $REVERSE_CIDRS ]]; then
REVERSE_CIDRS="in-addr.arpa ip6.arpa"
fi
if [[ -z $CLUSTER_DNS_IP ]]; then
# Default IP to kube-dns IP
CLUSTER_DNS_IP=$(kubectl get service --namespace kube-system kube-dns -o jsonpath="{.spec.clusterIP}")
if [ $? -ne 0 ]; then
>&2 echo "Error! The IP address for DNS service couldn't be determined automatically. Please specify the DNS-IP with the '-i' option."
exit 2
fi
fi
if [[ "${SKIP}" -ne 1 ]] ; then
translate-kube-dns-configmap
fi
orig=$'\n'
replace=$'\\\n'
sed -e "s/CLUSTER_DNS_IP/$CLUSTER_DNS_IP/g" \
-e "s/CLUSTER_DOMAIN/$CLUSTER_DOMAIN/g" \
-e "s?REVERSE_CIDRS?$REVERSE_CIDRS?g" \
-e "s@STUBDOMAINS@${STUBDOMAINS//$orig/$replace}@g" \
-e "s/UPSTREAMNAMESERVER/$UPSTREAM/g" \
"${YAML_TEMPLATE}"
kubectl apply ... 安装部署
https://coredns.io/plugins/loop#troubleshooting:
一段关于CrashLoopBackOff的说明
When a CoreDNS Pod deployed in Kubernetes detects a loop, the CoreDNS Pod will start to “CrashLoopBackOff”. This is because Kubernetes will try to restart the Pod every time CoreDNS detects the loop and exits.
A common cause of forwarding loops in Kubernetes clusters is an interaction with a local DNS cache on the host node (e.g. systemd-resolved). For example, in certain configurations systemd-resolved will put the loopback address 127.0.0.53 as a nameserver into /etc/resolv.conf. Kubernetes (via kubelet) by default will pass this /etc/resolv.conf file to all Pods using the default dnsPolicy rendering them unable to make DNS lookups (this includes CoreDNS Pods). CoreDNS uses this /etc/resolv.conf as a list of upstreams to forward requests to. Since it contains a loopback address, CoreDNS ends up forwarding requests to itself.
There are many ways to work around this issue, some are listed here:
- Add the following to your kubelet config yaml: resolvConf: (or via command line flag --resolv-conf deprecated in 1.10). Your “real” resolv.conf is the one that contains the actual IPs of your upstream servers, and no local/loopback address. This flag tells kubelet to pass an alternate resolv.conf to Pods. For systems using systemd-resolved, /run/systemd/resolve/resolv.conf is typically the location of the “real” resolv.conf, although this can be different depending on your distribution.
- Disable the local DNS cache on host nodes, and restore /etc/resolv.conf to the original.
- A quick and dirty fix is to edit your Corefile, replacing forward . /etc/resolv.conf with the IP address of your upstream DNS, for example forward . 8.8.8.8. But this only fixes the issue for CoreDNS, kubelet will continue to forward the invalid resolv.conf to all default dnsPolicy Pods, leaving them unable to resolve DNS
说明:
https://github.com/coredns/deployment 是他的针对不同环境的安装方式，包括debian,docker,以及kubernetes等的安装部署方式
请参考: https://github.com/coredns/deployment/tree/master/kubernetes
DescriptionCoreDNS can run in place of the standard Kube-DNS in Kubernetes. Using the kubernetes plugin, CoreDNS will read zone data from a Kubernetes cluster. It implements the spec defined for Kubernetes DNS-Based service discovery: https://github.com/kubernetes/dns/blob/master/docs/specification.md 我们看到这段阐述的就是coredns就是基于service的发现方式. |
kubectl apply -f coredns.yaml 安装之后
[root@k2 dns]# kubectl get ServiceAccount -n kube-system | grep coredns coredns 1 3y
[root@k2 dns]# kubectl get ClusterRole | grep 'system:coredns'
system:coredns 3y
[root@k2 dns]# kubectl get ClusterRoleBinding | grep 'system:coredns'
system:coredns 3y
[root@k2 dns]# kubectl get ConfigMap -n kube-system | grep 'coredns'
coredns 1 3y
//镜像coredns 1.1.1
[root@k2 dns]# kubectl get Deployment -n kube-system | grep 'coredns'
coredns 1 1 1 1 3y
[root@k2 dns]# kubectl get svc -n kube-system | grep 'kube-dns'
kube-dns ClusterIP 172.17.0.2 <none> 53/UDP,53/TCP 3y
配置内部kubeapiserver dns服务地址
[root@k2 conf]# vi /etc/kubenetes/conf/kubeapiserver
###
# 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="--advertise-address=10.129.55.112 --bind-address=10.129.55.112"
# The port on the local server to listen on.
KUBE_API_PORT="--secure-port=6443"
# Port minions listen on
# KUBELET_PORT="--kubelet-port=10250"
# Comma separated list of nodes in the etcd cluster
KUBE_ETCD_SERVERS="--etcd-servers=https://10.129.55.111:2379,https://10.129.55.112:2379,https://10.129.55.113:2379"
# Address range to use for services
KUBE_SERVICE_ADDRESSES="--service-cluster-ip-range=172.17.0.0/16"
# default admission control policies
KUBE_ADMISSION_CONTROL="--enable-admission-plugins=NamespaceLifecycle,LimitRanger,ServiceAccount,DefaultStorageClass,DefaultTolerationSeconds,MutatingAdmissionWebhook,ValidatingAdmissionWebhook,ResourceQuota,NodeRestriction"
# Add your own!
KUBE_API_ARGS=" --anonymous-auth=false \
--apiserver-count=3 \
--audit-log-maxage=30 \
--audit-log-maxbackup=3 \
--audit-log-maxsize=100 \
--audit-log-path=/var/log/kube-audit/audit.log \
--audit-policy-file=/etc/kubernetes/conf/audit-policy.yaml \
代码分析(coredns被放在了kubernetes统一的第三方插件目录addons下)
E:\k8s源码\kubernetes-1.10.13\kubernetes-1.10.13\cluster\addons\dns
我们看到coredns做了第三方的插件放到了上面的目录下
我这里有一篇翻译官方的插件(addons)
https://www.cnblogs.com/aozhejin/p/16270418.html
https://github.com/kubernetes/dns/blob/master/docs/specification.md
https://github.com/coredns/deployment/tree/master/kubernetes
https://github.com/containernetworking/cni/blob/main/SPEC.md#network-configuration-lists
https://github.com/containernetworking/cni/blob/main/CONVENTIONS.md
//kubernetes和coredns的版本对应关系
https://github.com/coredns/deployment/blob/master/kubernetes/CoreDNS-k8s_version.md
https://kubernetes.io/docs/concepts/cluster-administration/addons/ 标签：core,13,k8s,1.10,kubernetes,dns,coredns,kube,name From： https://www.cnblogs.com/aozhejin/p/16299818.html