Kubernetes/DNS - Revision history

Pio2pio: /* Trooubleshot core-dns */

2020-09-19T09:02:30Z

Trooubleshot core-dns

← Older revision		Revision as of 11:02, 19 September 2020
Line 165:		Line 165:
	# nslookup test 1		# nslookup test 1
	kubectl -n default run --image=busybox busybox-1 --rm -it -- sh		kubectl -n default run --image=busybox busybox-1 --rm -it -- sh
	/ # nslookup -type=A -debug wp.pl 8.8.8.8		/ $ nslookup -type=A -debug wp.pl 8.8.8.8
	Server: 8.8.8.8		Server: 8.8.8.8
	Address: 8.8.8.8:53		Address: 8.8.8.8:53

Pio2pio: /* Trooubleshot core-dns */

2020-09-19T09:01:05Z

Trooubleshot core-dns

← Older revision		Revision as of 11:01, 19 September 2020
Line 163:		Line 163:
	Example of info-logs		Example of info-logs
	<source lang=bash>		<source lang=bash>
	# ~~Nslookup~~ test ~~call~~		# nslookup test 1
	kubectl ~~exec~~ -it ~~busybox~~ -- ~~/bin/~~sh		kubectl -n default run --image=busybox busybox-1 --rm -it -- sh
	/ # nslookup kubernetes.default		/ # nslookup -type=A -debug wp.pl 8.8.8.8
			Server: 8.8.8.8
			Address: 8.8.8.8:53

			Query #0 completed in 18ms:
			Non-authoritative answer:
			Name: wp.pl
			Address: 212.77.98.9

			# nslookup test 2
			kubectl -n default run --image=busybox busybox-1 --rm -it -- nslookup kubernetes.default
			# \| Usage: nslookup [-type=QUERY_TYPE] [-debug] HOST [DNS_SERVER]

	# Watch logs using stern, sourceIP 10.1.1.1 it is busybox's pod IP		# Watch logs using stern, sourceIP 10.1.1.1 it is busybox's pod IP
	# On EKS, it's an secondary-IP assigned to the node ~~the~~ busybox pod is running on		# \| on EKS, it's a secondary-IP assigned to the node <code>busybox</code> pod is running on
	$ stern --all-namespaces core		$ stern --all-namespaces core
	kube-systemkube-system coredns-bb46f865d-vt82x coredns 2019-12-30T15:56:09.450Z [INFO] 10.1.1.1:51168 - 3 "AAAA IN kubernetes.default. udp 36 false 512" NXDOMAIN qr,rd,ra 111 0.000733313s		kube-systemkube-system coredns-bb46f865d-vt82x coredns 2019-12-30T15:56:09.450Z [INFO] 10.1.1.1:51168 - 3 "AAAA IN kubernetes.default. udp 36 false 512" NXDOMAIN qr,rd,ra 111 0.000733313s

Pio2pio: /* alias, rewrite */

2020-09-19T08:34:11Z

alias, rewrite

← Older revision		Revision as of 10:34, 19 September 2020
Line 111:		Line 111:
	== alias, rewrite ==		== alias, rewrite ==
	<syntaxhighlightjs lang="yaml">		<syntaxhighlightjs lang="yaml">
			# kubectl -n kube-system edit cm coredns
	.:53 {		.:53 {
	errors		errors
Line 122:		Line 123:
	}		}
	</syntaxhighlightjs>		</syntaxhighlightjs>


	== Trooubleshot core-dns ==		== Trooubleshot core-dns ==

Pio2pio: /* per pod dns settings nameservers, search, /etc/hosts */

2020-09-19T08:20:44Z

per pod dns settings nameservers, search, /etc/hosts

← Older revision		Revision as of 10:20, 19 September 2020
Line 96:		Line 96:
	- name: test		- name: test
	image: nginx		image: nginx
	dnsPolicy: "None" #do not inherit settings from a node		dnsPolicy: "None" # do not inherit settings from a node
	dnsConfig:		dnsConfig:
	nameservers:		nameservers:

Pio2pio: /* per pod dns settings nameservers, search, /etc/hosts */

2020-09-19T08:20:25Z

per pod dns settings nameservers, search, /etc/hosts

← Older revision		Revision as of 10:20, 19 September 2020
Line 86:		Line 86:

	== per pod dns settings nameservers, search, /etc/hosts ==		== per pod dns settings nameservers, search, /etc/hosts ==
	<~~source~~ lang=yaml>		<syntaxhighlightjs lang="yaml">
	apiVersion: v1		apiVersion: v1
	kind: Pod		kind: Pod
Line 107:		Line 107:
	value: "3"		value: "3"
	- name: edns0		- name: edns0
	</~~source~~>		</syntaxhighlightjs>

	== alias, rewrite ==		== alias, rewrite ==

Pio2pio: /* coredns configuration */

2020-09-19T08:20:00Z

coredns configuration

← Older revision		Revision as of 10:20, 19 September 2020
Line 82:		Line 82:
	</source>		</source>

	=coredns ~~configuration~~=		=[https://coredns.io/2017/05/08/custom-dns-entries-for-kubernetes/ Custom DNS Entries For Kubernetes]=
	Custom dns settings can be set per pod basis. Default is cluster first, pod inherits DNS settings from a node it's running on		Custom dns settings can be set per pod basis. Default is cluster first, pod inherits DNS settings from a node it's running on

			== per pod dns settings nameservers, search, /etc/hosts ==
	<source lang=yaml>		<source lang=yaml>
	apiVersion: v1		apiVersion: v1
Line 106:		Line 108:
	- name: edns0		- name: edns0
	</source>		</source>

			== alias, rewrite ==
			<syntaxhighlightjs lang="yaml">
			.:53 {
			errors
			log
			health
			rewrite name foo.example.com foo.default.svc.cluster.local
			kubernetes cluster.local 10.0.0.0/24
			file /etc/coredns/example.db example.org
			proxy . /etc/resolv.conf
			cache 30
			}
			</syntaxhighlightjs>

Pio2pio: /* Troubleshot core-dns */

2020-09-19T08:15:38Z

Troubleshot core-dns

← Older revision		Revision as of 10:15, 19 September 2020
Line 108:		Line 108:


	== ~~Troubleshot~~ core-dns ==		== Trooubleshot core-dns ==
	Coredns runs as pods		Coredns runs as pods
	<source lang=bash>		<source lang=bash>

Pio2pio: /* Headless services */

2020-09-19T08:12:57Z

Headless services

← Older revision		Revision as of 10:12, 19 September 2020
Line 66:		Line 66:


	=Headless ~~services~~=		=Headless service=
	Headless services, its a service without a clusterIP, will respond with set of IPs that belong to a POD. These IPs are current IPs that service consider healthy pods.		Headless services, its a service without a clusterIP, will respond with set of IPs that belong to a POD. These IPs are current IPs that service consider healthy pods.
	<source lang=yaml>		<source lang=yaml>
Line 81:		Line 81:
	app: kubserve2		app: kubserve2
	</source>		</source>


	=coredns configuration=		=coredns configuration=

Pio2pio: /* DNS */

2020-09-19T08:12:33Z

DNS

← Older revision		Revision as of 10:12, 19 September 2020
Line 66:		Line 66:


			=Headless services=
	Headless services, its a service without a clusterIP, will respond with set of IPs that belong to a POD. These IPs are current IPs that service consider healthy pods.		Headless services, its a service without a clusterIP, will respond with set of IPs that belong to a POD. These IPs are current IPs that service consider healthy pods.
	<source lang=yaml>		<source lang=yaml>
Line 82:		Line 83:


			=coredns configuration=
	Custom dns settings can be set per pod basis. Default is cluster first, pod inherits DNS settings from a node it's running on		Custom dns settings can be set per pod basis. Default is cluster first, pod inherits DNS settings from a node it's running on
	<source lang=yaml>		<source lang=yaml>

Pio2pio: Created page with "= DNS = Since 1.13, CoreOS has replaced `kube-dns with core-dns written in Go. It supports DNS over TLS in short dot. core-dns pods are runni..."`

2020-09-19T08:10:05Z Created page with "= DNS = Since 1.13, CoreOS has replaced <tt>kube-dns<tt> with <tt>core-dns</tt> written in Go. It supports DNS over TLS in short <tt>dot</tt>. <tt>core-dns</tt> pods are runni..." New page = DNS = Since 1.13, CoreOS has replaced <tt>kube-dns<tt> with <tt>core-dns</tt> written in Go. It supports DNS over TLS in short <tt>dot</tt>. <tt>core-dns</tt> pods are running as a deployment. <source lang=bash> #svc-name ns /BaseDomainName\ kubernetes.default.svc.cluster.local 10-10-20-1.default.pod.cluster.local #pod ip ns \BaseDomainName/ </source> Core-dns runs as a deployment <source lang=bash> kubectl -n kube-system get pod -owide | grep core coredns-86c58d9df4-7dl5d 1/1 Running 59 12d 10.100.0.18 master-1.acme.com <none> <none> coredns-86c58d9df4-rsxct 1/1 Running 59 12d 10.100.0.19 master-1.acme.com <none> <none> kubectl -n kube-system get deployments -owide NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR coredns 2/2 2 2 12d coredns k8s.gcr.io/coredns:1.2.6 k8s-app=kube-dns #Service that perform LoadBalancing. note it's named 'kube-dns' to support backward compatibnility for workloads relaying on kube-dns ubectl -n kube-system get service -owide NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR kube-dns ClusterIP 10.96.0.10 <none> 53/UDP,53/TCP 12d k8s-app=kube-dns </source> Interact with DNS, using BusyBox container <source lang=yaml> apiVersion: v1 kind: Pod metadata: name: busybox namespace: default spec: containers: - image: busybox:1.28.4 command: - sleep - "3600" imagePullPolicy: IfNotPresent name: busybox restartPolicy: Always #Deploy kubectl apply -f busybox.yaml #Verify dns settings kubectl exec -t busybox -- cat /etc/resolv.conf nameserver 10.96.0.10 search default.svc.cluster.local svc.cluster.local cluster.local mylabserver.com options ndots:5 #Check DNS operations kubectl exec -it busybox -- nslookup <service-name> kubectl exec -it busybox -- nslookup <pod-ip-v-4>.default.pod.cluster.local #pod kubectl exec -it busybox -- nslookup <svcName>.default.svc.cluster.local #service kubectl exec -it busybox -- nslookup kube-dns.kube-system.svc.cluster.local #service </source> CoreDNS manages following records for Services: * A records (not headless) - Services are assigned a DNS A record for a name of the form my-svc.my-namespace.svc.cluster-domain.example. This resolves to the cluster IP of the Service. * A records (headless without cluster IP) - Services are also assigned a DNS A record for a name of the form my-svc.my-namespace.svc.cluster-domain.example. Unlike normal Services, this resolves to the set of IPs of the pods selected by the Service * SRV records - SRV Records are created for named ports that are part of normal or Headless Services. [https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/#srv-records read more...] Headless services, its a service without a clusterIP, will respond with set of IPs that belong to a POD. These IPs are current IPs that service consider healthy pods. <source lang=yaml> apiVersion: v1 kind: Service metadata: name: kube-headless spec: clusterIP: None #set to none ports: - port: 80 targetPort: 8080 selector: app: kubserve2 </source> Custom dns settings can be set per pod basis. Default is cluster first, pod inherits DNS settings from a node it's running on <source lang=yaml> apiVersion: v1 kind: Pod metadata: namespace: default name: pod-dns-custom-setup spec: containers: - name: test image: nginx dnsPolicy: "None" #do not inherit settings from a node dnsConfig: nameservers: - 8.8.4.4 searches: - ns1.svc.cluster.local - my.dns.search.suffix options: - name: ndots value: "3" - name: edns0 </source> == Troubleshot core-dns == Coredns runs as pods <source lang=bash> kubectl -n kube-system get pods | grep dns coredns-86c58d9df4-7dl5d 1/1 Running 60 13d coredns-86c58d9df4-rsxct 1/1 Running 60 13d </source> See logs <source lang=bash> kubectl -n kube-system logs coredns-86c58d9df4-7dl5d -f .:53 2019-07-18T06:33:08.165Z [INFO] CoreDNS-1.2.6 2019-07-18T06:33:08.165Z [INFO] linux/amd64, go1.11.2, 756749c CoreDNS-1.2.6 linux/amd64, go1.11.2, 756749c [INFO] plugin/reload: Running configuration MD5 = f65c4821c8a9b7b5eb30fa4fbc167769 [ERROR] plugin/errors: 2 8726527267836830687.8090630885983783330. HINFO: unreachable backend: read udp 10.100.0.20:33021->172.31.0.2:53: i/o timeout </source> Enable resolution logs, the config reload may take a minute or two <source lang=bash> kubectl -n kube-system edit cm coredns apiVersion: v1 data: Corefile: | .:53 { log # <- add info logs errors health .. </source> Example of info-logs <source lang=bash> # Nslookup test call kubectl exec -it busybox -- /bin/sh / # nslookup kubernetes.default # Watch logs using stern, sourceIP 10.1.1.1 it is busybox's pod IP # On EKS, it's an secondary-IP assigned to the node the busybox pod is running on $ stern --all-namespaces core kube-systemkube-system coredns-bb46f865d-vt82x coredns 2019-12-30T15:56:09.450Z [INFO] 10.1.1.1:51168 - 3 "AAAA IN kubernetes.default. udp 36 false 512" NXDOMAIN qr,rd,ra 111 0.000733313s coredns-bb46f865d-dsfkv coredns 2019-12-30T15:56:09.449Z [INFO] 10.1.1.1:50216 - 2 "PTR IN 10.0.20.172.in-addr.arpa. udp 42 false 512" NOERROR qr,aa,rd 118 0.000258372s kube-system coredns-bb46f865d-dsfkv coredns 2019-12-30T15:56:09.451Z [INFO] 10.1.1.1:51070 - 4 "AAAA IN kubernetes.default.default.svc.cluster.local. udp 62 false 512" NXDOMAIN qr,aa,rd 155 0.000145002s kube-system coredns-bb46f865d-dsfkv coredns 2019-12-30T15:56:09.452Z [INFO] 10.1.1.1:38472 - 5 "AAAA IN kubernetes.default.svc.cluster.local. udp 54 false 512" NOERROR qr,aa,rd 147 0.000097828s kube-system coredns-bb46f865d-dsfkv coredns 2019-12-30T15:56:09.456Z [INFO] 10.1.1.1:48263 - 6 "A IN kubernetes.default. udp 36 false 512" NXDOMAIN qr,rd,ra 111 0.002978255s kube-system coredns-bb46f865d-dsfkv kube-system coredns 2019-12-30T15:56:09.456Z [INFO] 10.1.1.1:50766 - 7 "A IN kubernetes.default.default.svc.cluster.local. udp 62 false 512" NXDOMAIN qr,aa,rd 155 0.000099745s coredns-bb46f865d-vt82x coredns 2019-12-30T15:56:09.457Z [INFO] 10.1.1.1:40487 - 8 "A IN kubernetes.default.svc.cluster.local. udp 54 false 512" NOERROR qr,aa,rd 106 0.000107216s kube-system coredns-bb46f865d-vt82x coredns 2019-12-30T15:56:09.458Z [INFO] 10.1.1.1:45808 - 9 "PTR IN 1.0.20.172.in-addr.arpa. udp 41 false 512" NOERROR qr,aa,rd 114 0.000087131s </source>

Kubernetes/DNS - Revision history

Pio2pio: /* Trooubleshot core-dns */

Pio2pio: /* Trooubleshot core-dns */

Pio2pio: /* alias, rewrite */

Pio2pio: /* per pod dns settings nameservers, search, /etc/hosts */

Pio2pio: /* per pod dns settings nameservers, search, /etc/hosts */

Pio2pio: /* coredns configuration */

Pio2pio: /* Troubleshot core-dns */

Pio2pio: /* Headless services */

Pio2pio: /* DNS */

Pio2pio: Created page with "= DNS = Since 1.13, CoreOS has replaced kube-dns with core-dns written in Go. It supports DNS over TLS in short dot. core-dns pods are runni..."

Pio2pio: Created page with "= DNS = Since 1.13, CoreOS has replaced `kube-dns with core-dns written in Go. It supports DNS over TLS in short dot. core-dns pods are runni..."`