Update docs

Author: m99coder

README.md

@@ -4,16 +4,16 @@ PostgreSQL on Kubernetes
 ## Prerequisites
 
 ```bash
-# install minikube to create a single-node cluster
-brew install minikube
+$ # install minikube to create a single-node cluster
+$ brew install minikube
 
-# start cluster using VMs
-minikube start --vm=true
+$ # start cluster using VMs
+$ minikube start --vm=true
 
-# create a custom namespace and context
-kubectl create namespace postgres
-kubectl config set-context postgres --namespace postgres --cluster minikube --user minikube
-kubectl config use-context postgres
+$ # create a custom namespace and context
+$ kubectl create namespace postgres
+$ kubectl config set-context postgres --namespace postgres --cluster minikube --user minikube
+$ kubectl config use-context postgres
 ```
 
 ## Persistent Volumes
@@ -23,13 +23,13 @@ In order to persist the data stored in PostgreSQL it’s necessary to create [Pe
 There are two ways to create Persistent Volumes. Either you manually create a volume per replica of PostgreSQL or you configure [dynamic provisioning](https://minikube.sigs.k8s.io/docs/handbook/persistent_volumes/#dynamic-provisioning-and-csi). For simplicity we choose the manual approach first.
 
 ```bash
-# create 3 persistent volumes
-kubectl apply -f pv-0.yaml
-kubectl apply -f pv-1.yaml
-kubectl apply -f pv-2.yaml
+$ # create 3 persistent volumes
+$ kubectl apply -f pv-0.yaml
+$ kubectl apply -f pv-1.yaml
+$ kubectl apply -f pv-2.yaml
 
-# list persistent volumes
-kubectl get pv
+$ # list persistent volumes
+$ kubectl get pv
 NAME              CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS   REASON   AGE
 pv-postgresql-0   1Gi        RWO            Retain           Available           default                 9s
 pv-postgresql-1   1Gi        RWO            Retain           Available           default                 7s
@@ -41,11 +41,11 @@ pv-postgresql-2   1Gi        RWO            Retain           Available
 A [Headless Service](https://kubernetes.io/docs/concepts/services-networking/service/#headless-services) is specified with `clusterIP: None` and omits to use a L4 load balancer. By also defining a selector, the endpoints controller creates `Endpoint` records and also modifies the DNS configuration so that `A` records are returned that point directly to the pods.
 
 ```bash
-# create headless service
-kubectl apply -f svc.yaml
+$ # create headless service
+$ kubectl apply -f svc.yaml
 
-# describe headless service
-kubectl describe svc postgresql-svc
+$ # describe headless service
+$ kubectl describe svc postgresql-svc
 Name:              postgresql-svc
 Namespace:         postgres
 Labels:            sfs=postgresql-sfs
@@ -68,11 +68,11 @@ Events:            <none>
 PostgreSQL uses environment variables for configuration. The most important one for the official [PostgreSQL Docker image](https://hub.docker.com/_/postgres) is `POSTGRES_PASSWORD`. We utilize [Secrets](https://kubernetes.io/docs/concepts/configuration/secret/) to inject the respective value into the container later on.
 
 ```bash
-# create secret from literal
-kubectl create secret generic postgresql-secrets --from-literal=POSTGRES_PASSWORD=tes6Aev8
+$ # create secret from literal
+$ kubectl create secret generic postgresql-secrets --from-literal=POSTGRES_PASSWORD=tes6Aev8
 
-# describe secret
-kubectl describe secrets postgresql-secrets
+$ # describe secret
+$ kubectl describe secrets postgresql-secrets
 Name:         postgresql-secrets
 Namespace:    postgres
 Labels:       <none>
@@ -90,23 +90,23 @@ POSTGRES_PASSWORD:  8 bytes
 A [Stateful Set](https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/) is similar to a _Replica Set_ in a sense that it also handles pods for the configured number of replicas. In contrast to a _Replica Set_, it maintains a sticky identity for each of them. This means they are created in a fixed, sequential order and deleted counterwise. Their network identity is stable as well, what enables us to reference them by the automatically assigned DNS host inside of the cluster.
 
 ```bash
-# create stateful set with 3 replicas
-kubectl apply -f sfs.yaml
+$ # create stateful set with 3 replicas
+$ kubectl apply -f sfs.yaml
 
-# list stateful sets
-kubectl get statefulsets
+$ # list stateful sets
+$ kubectl get statefulsets
 NAME             READY   AGE
 postgresql-sfs   3/3     16s
 
-# list pods
-kubectl get pods
+$ # list pods
+$ kubectl get pods
 NAME               READY   STATUS    RESTARTS   AGE
 postgresql-sfs-0   1/1     Running   0          86s
 postgresql-sfs-1   1/1     Running   0          83s
 postgresql-sfs-2   1/1     Running   0          80s
 
-# inspect logs of a random pod
-kubectl logs postgresql-sfs-0
+$ # inspect logs of a random pod
+$ kubectl logs postgresql-sfs-0
 
 PostgreSQL Database directory appears to contain a database; Skipping initialization
 
@@ -117,8 +117,8 @@ PostgreSQL Database directory appears to contain a database; Skipping initializa
 2021-08-04 08:19:50.838 UTC [26] LOG:  database system was shut down at 2021-08-03 14:33:17 UTC
 2021-08-04 08:19:50.843 UTC [1] LOG:  database system is ready to accept connections
 
-# describe the service to see that 3 endpoints were created automatically
-kubectl describe svc postgresql-svc
+$ # describe the service to see that 3 endpoints were created automatically
+$ kubectl describe svc postgresql-svc
 Name:              postgresql-svc
 Namespace:         postgres
 Labels:            sfs=postgresql-sfs
@@ -141,7 +141,7 @@ Events:            <none>
 You are able to directly connect to PostgreSQL by starting `bash` within a particular pod.
 
 ```bash
-kubectl exec -it postgresql-sfs-0 -- bash
+$ kubectl exec -it postgresql-sfs-0 -- bash
 root@postgresql-sfs-0:/# PGPASSWORD=tes6Aev8 psql -U postgres
 psql (13.3 (Debian 13.3-1.pgdg100+1))
 Type "help" for help.
@@ -154,7 +154,9 @@ exit
 An alternative approach is running a temporary PostgreSQL container and using the included `psql` to connect to one of the database instances. Where the hostname is the automatically created DNS host of the service we deployed earlier. The format of that hostname is: `<service-name>.<namespace>.svc.cluster.local` and will be resolved to a random pod running a database server.
 
 ```bash
-kubectl run -it --rm pg-psql --image=postgres:13.3 --restart=Never --env="PGPASSWORD=tes6Aev8" -- psql -h postgresql-svc.postgres.svc.cluster.local -U postgres
+$ kubectl run -it --rm pg-psql --image=postgres:13.3 --restart=Never \
+    --env="PGPASSWORD=tes6Aev8" -- \
+    psql -h postgresql-svc.postgres.svc.cluster.local -U postgres
 If you don't see a command prompt, try pressing enter.
 postgres=# \q
 pod "pg-psql" deleted
@@ -163,7 +165,7 @@ pod "pg-psql" deleted
 To check that the DNS hostname works we deploy a busybox instance.
 
 ```bash
-kubectl run -it --rm busybox --image=busybox --restart=Never -- sh
+$ kubectl run -it --rm busybox --image=busybox --restart=Never -- sh
 If you don't see a command prompt, try pressing enter.
 / # ping postgresql-svc.postgres.svc.cluster.local
 PING postgresql-svc.postgres.svc.cluster.local (172.17.0.3): 56 data bytes