Update readme and add description for snapshot creation

Readme.md

@@ -3,5 +3,44 @@ This is a custom elasticsearch image with the elastic image as a base and the s3
 
 ## Build
 ```bash
-docker build --build-arg elasticsearch_version=7
+docker build --build-arg elasticsearch_version=7.9.3
 ```
+
+## Snapshot key
+We use keystore to store s3 key and secrete as [recommended by elastic](https://github.com/elastic/helm-charts/blob/master/elasticsearch/README.md#how-to-use-the-keystore). Check the deployment of the es-cluster to see how we use the secrets.
+
+```
+kubectl create secret generic s3-access-key --from-literal=s3.client.default.access_key=''
+kubectl create secret generic s3-secret-key --from-literal=s3.client.default.secret_key=''
+```
+
+## Config Snapshots S3
+To use the [s3 plugin](https://www.elastic.co/guide/en/elasticsearch/plugins/6.8/repository-s3-repository.html) with Digital Ocean we need to configure a s3 repository for the backup. We use the official helm repo. Checkout the docu for [snapshots](https://github.com/elastic/helm-charts/tree/master/elasticsearch#how-to-enable-snapshotting).
+```bash
+kubectl port-forward service/elasticsearch-master-headless 9200:9200
+curl --location --request PUT 'localhost:9200/_snapshot/metagrid-backup-es-7' \
+--header 'Content-Type: application/json' \
+--data-raw '{
+  "type": "s3",
+  "settings": {
+    "endpoint": "fra1.digitaloceanspaces.com",
+    "bucket": "metagrid-backup-es-7"
+  }
+}'
+```
+
+## Take a snapshot S3
+To use the s3 plugin with Digital Ocean we need to configure a s3 repository for the backup.
+```bash
+kubectl port-forward service/elasticsearch-master-headless 9200:9200
+curl --location --request PUT 'localhost:9200/_snapshot/metagrid-backup-es-7/%3Csnapshot-%7Bnow%2Fd%7D%3E' \
+--header 'Content-Type: application/json'
+```
+
+## Check snapshot status
+You may want to know when the snapshot is finished.
+```bash
+curl --location --request GET 'localhost:9200/_snapshot/metagrid-backup-es-7/%3Csnapshot-%7Bnow%2Fd%7D%3E' \
+--header 'Content-Type: application/json'
+```
+You should log into Digital ocean Dashboard and check the spaces if there are new files.