Understanding your cluster
Elasticsearch has many different moving parts, and it can get a little complicated to ensure that everything runs properly. Fortunately, there are some great open source monitoring tools that are available to help you keep tabs on your cluster. This section will cover how to install some of the most popular and useful monitoring tools on your cluster, and the following two chapters will go into these tools in more detail.
Installing Elasticsearch-head
Elasticsearch-head is a simple, free, open source tool that provides a high-level examination of your cluster. It is one of the most useful tools used when administering and monitoring the health of a cluster. Elasticsearch-head only needs to be installed on one node in your cluster. However, we recommend installing it on all nodes for redundancy. It's installed as an Elasticsearch plugin.
If you have an Internet connection, you can install Elasticsearch-head with the Elasticsearch plugin utility, as follows:
sudo...
