make elasticsearch work as a single-node and limit ram

vm/install_elasticsearch.sh

@@ -3,6 +3,14 @@ curl -sL https://artifacts.elastic.co/GPG-KEY-elasticsearch | sudo apt-key add -
 echo "deb https://artifacts.elastic.co/packages/7.x/apt stable main" > /etc/apt/sources.list.d/elasticsearch.list
 apt-get update -qq
 apt-get -y install elasticsearch
+cat >> /etc/elasticsearch/elasticsearch.yml << EOF
+xpack.security.enabled: false
+discovery.type: single-node
+EOF
+cat > /etc/elasticsearch/jvm.options.d/mem.options << EOF
+-Xms8g
+-Xmx8g
+EOF
 systemctl enable elasticsearch.service
 systemctl start elasticsearch.service
 #curl -X GET "http://localhost:9200/?pretty"