This is totally cribbed from here -> Debugging DNS Resolution
Create dnsutils.yaml file
cat << EOF > ~/dnsutils.yaml
apiVersion: v1
kind: Pod
metadata:
name: dnsutils
namespace: default
spec:
containers:
- name: dnsutils
image: gcr.io/kubernetes-e2e-test-images/dnsutils:1.3
command:
- sleep
- "3600"
imagePullPolicy: IfNotPresent
restartPolicy: Always
EOF
Validate YAML
cat ~/dnsutils.yaml
apiVersion: v1
kind: Pod
metadata:
name: dnsutils
namespace: default
spec:
containers:
- name: dnsutils
image: gcr.io/kubernetes-e2e-test-images/dnsutils:1.3
command:
- sleep
- "3600"
imagePullPolicy: IfNotPresent
restartPolicy: Always
Apply to cluster
kubectl apply -f ~/dnsutils.yaml
pod/dnsutils created
Check running pods
kubectl get pods
NAME READY STATUS RESTARTS AGE
dnsutils 1/1 Running 0 47s
Use dnsutils to lookup default K8s servicename
kubectl exec -ti dnsutils -- nslookup kubernetes.default
Server:10.96.0.10
Address:10.96.0.10#53
Name:kubernetes.default.svc.cluster.local
Address: 10.96.0.1
Use dnsutils to inspect /etc/resolv.conf
kubectl exec -ti dnsutils -- cat /etc/resolv.conf
nameserver 10.96.0.10
search default.svc.cluster.local svc.cluster.local cluster.local
options ndots:5
Use dnsutils to get help for the ping command
kubectl exec -ti dnsutils -- ping --help
BusyBox v1.26.2 (2018-05-30 13:53:45 GMT) multi-call binary.
Usage: ping [OPTIONS] HOST
Send ICMP ECHO_REQUEST packets to network hosts
-4,-6Force IP or IPv6 name resolution
-c CNTSend only CNT pings
-s SIZESend SIZE data bytes in packets (default:56)
-t TTLSet TTL
-I IFACE/IPUse interface or IP address as source
-W SECSeconds to wait for the first response (default:10)
(after all -c CNT packets are sent)
-w SECSeconds until ping exits (default:infinite)
(can exit earlier with -c CNT)
-qQuiet, only display output at start
and when finished
-pPattern to use for payload
Use dnsutils to ping google.com
kubectl exec -ti dnsutils -- ping www.google.com
PING www.google.com (172.217.2.100): 56 data bytes
64 bytes from 172.217.2.100: seq=0 ttl=114 time=1.216 ms
64 bytes from 172.217.2.100: seq=1 ttl=114 time=1.328 ms
64 bytes from 172.217.2.100: seq=2 ttl=114 time=1.344 ms
64 bytes from 172.217.2.100: seq=3 ttl=114 time=1.278 ms
64 bytes from 172.217.2.100: seq=4 ttl=114 time=1.483 ms
64 bytes from 172.217.2.100: seq=5 ttl=114 time=1.393 ms
64 bytes from 172.217.2.100: seq=6 ttl=114 time=1.227 ms
64 bytes from 172.217.2.100: seq=7 ttl=114 time=1.343 ms
^C
--- www.google.com ping statistics ---
8 packets transmitted, 8 packets received, 0% packet loss
round-trip min/avg/max = 1.216/1.326/1.483 ms
Use dnsutils to send only 5 pings to google.com
kubectl exec -ti dnsutils -- ping -c 5 www.google.com
PING www.google.com (172.217.2.100): 56 data bytes
64 bytes from 172.217.2.100: seq=0 ttl=114 time=1.382 ms
64 bytes from 172.217.2.100: seq=1 ttl=114 time=1.480 ms
64 bytes from 172.217.2.100: seq=2 ttl=114 time=1.414 ms
64 bytes from 172.217.2.100: seq=3 ttl=114 time=1.326 ms
64 bytes from 172.217.2.100: seq=4 ttl=114 time=1.276 ms
--- www.google.com ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max = 1.276/1.375/1.480 ms
Use dnsutils to ping google.com with a 5-second Time To Live (TTL)
kubectl exec -ti dnsutils -- ping -t 5 www.google.com
PING www.google.com (172.217.2.100): 56 data bytes
^C
--- www.google.com ping statistics ---
276 packets transmitted, 0 packets received, 100% packet loss
Use dnsutils to ping google.com with a 5 second wait
kubectl exec -ti dnsutils -- ping -w 5 www.google.com
PING www.google.com (172.217.2.100): 56 data bytes
64 bytes from 172.217.2.100: seq=0 ttl=114 time=1.153 ms
64 bytes from 172.217.2.100: seq=1 ttl=114 time=1.660 ms
64 bytes from 172.217.2.100: seq=2 ttl=114 time=1.312 ms
64 bytes from 172.217.2.100: seq=3 ttl=114 time=1.144 ms
64 bytes from 172.217.2.100: seq=4 ttl=114 time=1.289 ms
--- www.google.com ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max = 1.144/1.311/1.660 ms
Delete pod
delete pod dnsutils
pod "dnsutils" deleted