Practical uses of Cluster RHEL 8

1. Introduction

a. A cluster is two or more computers (called nodes or members) that work together to perform a task.

Interview QA : Suppose you are going for a interview and interviewer ask you what is cluster ? At this point of time above definition will help you.

2. Pacemaker

a. It is a cluster resource manager and achieve maximum availability for your cluster services.

b. Four basic components of the pacemaker architecture components are as follows:

1. Cluster Information Base: uses XML internally to distribute and synchronize current configuration and status information from the designated coordinator.

2. Cluster Resource Management Daemon (CRMd): Each cluster node also includes a local resource manager daemon (LRMd) that acts as an interface between CRMd and resources.

3. STONITH: It is configured in CIB and can be monitored as a normal cluster resource.

4. Corosync: provides messaging capabilities for applications that coordinate or operate across multiple members of the cluster.

Interview QA :Suppose you are going for a interview and interviewer ask you what is pacemaker ? At this point of time above definition will help you.

3. Pacemaker configuration and management tools

a. Pacemaker features two configuration tools for cluster deployment, monitoring and management.

1. pcs: controls and configures pacemaker and the corosync heartbeat daemon.

2. pcsd Web UI: It is a graphical user interface to create and configure pacemaker/ corosync

clusters.

Interview QA : Suppose you are going for a interview and interviewer ask you what are the two configuration tools for cluster deployment , monitoring and management ? At this point of time above definition will help you.

4. Fence device

a. It is an external device that can be used by the cluster to restrict access to shared resources by an errant node, or to issue a hard reboot on the cluster node.

Interview QA : Suppose you are going for a interview and interviewer ask you what is fence device ? At this point of time above definition will help you.

5. Quorum

a. It is used to prevent data corruption and loss.

Interview QA : Suppose you are going for a interview and interviewer ask you what is the use of the quorum ? At this point of time above definition will help you.

6. Pacemaker Installation

a. Command: yum install pcs pacemaker fence-agents-all

Above command will install pcs , pacemaker and fence agents

b. Command: systemctl start pcsd.service

Command: systemctl enable pcsd.service

Above command will start and enable the pcsd service.

Interview QA : Suppose you are going for a interview and interviewer ask you how will you install pacemaker ? At this point of time above definition will help you.

7. Setting and authenticate password to the ha cluster.

a. Command: passwd hacluster

Above command set the password to the hacluster.

b. Command: pcs host auth z1.example.com

Above command will verify whether password is set or not.

Interview QA : Suppose you are going for a interview and interviewer ask you How to set and authenticate password to the ha cluster ? At this point of time above command will help you.

8. Cluster creation and cluster verification

Command: pcs cluster setup my_cluster --start z1.example.com

Above command will create a cluster with one member.

Command: pcs cluster status

Interview QA : Suppose you are going for a interview and interviewer ask you how to create cluster and do the verification ? At this point of time above command will help you.

9. Restore cluster services

Command: pcs cluster unstandby z1.example.com

Above command restore cluster services to the first node, take the node out of standby node.

Interview QA : Suppose you are going for a interview and interviewer ask you how to restore the cluster services ? At this point of time above command will help you.

10. Stopping cluster services

Command: pcs cluster stop --all

Above command stop the cluster services on both nodes.

Interview QA : Suppose you are going for a interview and interviewer ask you how to stop cluster services on both nodes ? At this point of time above command will help you.

If you want to know more Please click on below link:

https://www.amazon.com/Linux-Kuriosity/e/B07J129KG4?ref=sr_ntt_srch_lnk_2&qid=1556597655&sr=8-2