In Kubernetes, how does one select a pod by name in a service selector?

There is also option for you to define a service with no pod selector. and then manually map the Service to the network address and port where it’s running, by adding an Endpoint object manually.

Example for your reference :

Created two pods of type nginx

$ kubectl get all -o wide
NAME            READY   STATUS    RESTARTS   AGE     IP               NODE         NOMINATED NODE   READINESS GATES
pod/nginx-one   1/1     Running   0          4m56s   192.168.58.199   k8s-node02   <none>           <none>
pod/nginx-two   1/1     Running   0          4m50s   192.168.85.193   k8s-node01   <none>           <none>

NAME                        TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE     SELECTOR
service/kubernetes          ClusterIP   10.96.0.1       <none>        443/TCP   29m     <none>

Create two service using below yamls, Note no Pod selector field used on yaml below

service1.yaml

apiVersion: v1
kind: Service
metadata:
  name: nginx-one-service
spec:
  ports:
    - protocol: TCP
      port: 80

service2.yaml

apiVersion: v1
kind: Service
metadata:
  name: nginx-two-service
spec:
  ports:
    - protocol: TCP
      port: 80


$ kubectl get svc
NAME                TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
kubernetes          ClusterIP   10.96.0.1       <none>        443/TCP   32m
nginx-one-service   ClusterIP   10.102.230.78   <none>        80/TCP    7m16s
nginx-two-service   ClusterIP   10.98.86.67     <none>        80/TCP    6m56s

Describe the service and no end point are mapped since we gave no selector.

ubuntu@k8s-master:~$ kubectl describe service nginx-one-service
Name:              nginx-one-service
Namespace:         default
Labels:            <none>
Annotations:       <none>
Selector:          <none>
Type:              ClusterIP
IP:                10.102.230.78
Port:              <unset>  80/TCP
TargetPort:        80/TCP
Endpoints:         <none>
Session Affinity:  None
Events:            <none>

ubuntu@k8s-master:~$ kubectl describe service nginx-two-service
Name:              nginx-two-service
Namespace:         default
Labels:            <none>
Annotations:       <none>
Selector:          <none>
Type:              ClusterIP
IP:                10.98.86.67
Port:              <unset>  80/TCP
TargetPort:        80/TCP
Endpoints:         <none>
Session Affinity:  None
Events:            <none>

Now you can choose to map the end point manually using below yamls.

endpoint1.yaml

apiVersion: v1
kind: Endpoints
metadata:
  name: nginx-one-service
subsets:
  - addresses:
      - ip: 192.168.85.193
    ports:
      - port: 80

endpoint2.yaml

apiVersion: v1
kind: Endpoints
metadata:
  name: nginx-two-service
subsets:
  - addresses:
      - ip: 192.168.85.193
    ports:
      - port: 80

Now get endpoint on creation

$ kubectl get endpoints
NAME                ENDPOINTS             AGE
kubernetes          131.160.188.46:6443   35m
nginx-one-service   192.168.58.199:80     5m30s
nginx-two-service   192.168.85.193:80     4m59s

and list the servie and endpoint should be mapped as below

ubuntu@k8s-master:~$ kubectl describe service nginx-one-service
Name:              nginx-one-service
Namespace:         default
Labels:            <none>
Annotations:       <none>
Selector:          <none>
Type:              ClusterIP
IP:                10.102.230.78
Port:              <unset>  80/TCP
TargetPort:        80/TCP
Endpoints:         192.168.58.199:80
Session Affinity:  None
Events:            <none>

ubuntu@k8s-master:~$ kubectl describe service nginx-two-service
Name:              nginx-two-service
Namespace:         default
Labels:            <none>
Annotations:       <none>
Selector:          <none>
Type:              ClusterIP
IP:                10.98.86.67
Port:              <unset>  80/TCP
TargetPort:        80/TCP
Endpoints:         192.168.85.193:80
Session Affinity:  None
Events:            <none>