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persistentvolume/readme.md

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+# Persistent Volumes Demo
+
+## Container Storage
+
+By default containers store their data on the file system like any other process.
+Container file system is temporary and not persistent during container restarts
+When container is recreated, so is the file system
+
+
+
+```
+# run postgres
+docker run -d --rm -e POSTGRES_DB=postgresdb -e POSTGRES_USER=admin -e POSTGRES_PASSWORD=admin123 postgres:10.4
+
+# enter the container 
+docker exec -it <container-id> bash
+
+# login to postgres
+psql --username=admin postgresdb
+
+#create a table
+CREATE TABLE COMPANY(
+   ID INT PRIMARY KEY     NOT NULL,
+   NAME           TEXT    NOT NULL,
+   AGE            INT     NOT NULL,
+   ADDRESS        CHAR(50),
+   SALARY         REAL
+);
+
+#show table
+\dt
+
+# quit 
+\q
+```
+
+Restarting the above container and going back in you will notice `\dt` commands returning no tables.
+Since data is lost.
+
+Same can be demonstrated using Kubernetes
+
+```
+cd .\kubernetes\persistentvolume\
+
+kubectl create ns postgres
+kubectl apply -n postgres -f ./postgres-no-pv.yaml
+kubectl -n postgres get pods 
+kubectl -n postgres exec -it postgres-0 bash
+
+# run the same above mentioned commands to create and list the database table
+
+kubectl delete po -n postgres postgres-0
+
+# exec back in and confirm table does not exist.
+```
+
+# Persist data Docker
+
+```
+docker volume create postges
+docker run -d --rm -v postges:/var/lib/postgresql/data -e POSTGRES_DB=postgresdb -e POSTGRES_USER=admin -e POSTGRES_PASSWORD=admin123 postgres:10.4
+
+# run the same tests as above and notice
+```
+
+# Persist data Kubernetes
+
+
+```
+kubectl apply -f persistentvolume.yaml
+kubectl apply -n postgres -f persistentvolumeclaim.yaml
+
+kubectl apply -n postgres -f postgres-with-pv.yaml
+
+kubectl -n postgres get pods
+
+```