10. Resource Manager on CentOS 7 | CentOS High Availability

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Table Of Contents

CentOS High Availability

By : Resman

4.5 (12)

CentOS High Availability

4.5 (12)

By: Resman

Overview of this book

This book is targeted at system engineers and system administrators who want to upgrade their knowledge and skills in high availability and want to learn practically how to achieve high availability with CentOS Linux. You are expected to have good CentOS Linux knowledge and basic networking experience.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

1. Getting Started with High Availability

1. Getting Started with High Availability

What is high availability?

System design

Computer clusters

High-availability solutions

Summary

2. Meet the Cluster Stack on CentOS

2. Meet the Cluster Stack on CentOS

Cluster stack software

The cluster communication layer

The cluster resource management layer

A theoretical cluster service example

Cluster stack on CentOS Linux

Preparing for cluster stack software installation

Summary

3. Cluster Stack Software on CentOS 6

3. Cluster Stack Software on CentOS 6

Cluster infrastructure

Cluster operating system preparation

Installing and configuring Corosync

Installing and configuring CMAN

Summary

4. Resource Manager on CentOS 6

4. Resource Manager on CentOS 6

Working with RGManager

Configuring failover domains

Adding cluster resources and services

Managing cluster services

Removing cluster resources and services

Summary

5. Playing with Cluster Nodes on CentOS 6

5. Playing with Cluster Nodes on CentOS 6

Adding a new cluster node

Removing a cluster node

Summary

6. Fencing on CentOS 6

6. Fencing on CentOS 6

Fencing

Fencing configuration

IPMI management board fencing

HP iLO management board fencing

Fencing test

Summary

7. Testing Failover on CentOS 6

7. Testing Failover on CentOS 6

Hardware failure

Network failure

Summary

8. Two-node Cluster Considerations on CentOS 6

8. Two-node Cluster Considerations on CentOS 6

Quorum in a two-node cluster

Two-node cluster configuration

Quorum disk

Summary

9. Cluster Stack Software on CentOS 7

9. Cluster Stack Software on CentOS 7

Cluster infrastructure

Installing and configuring Corosync

Summary

10. Resource Manager on CentOS 7

10. Resource Manager on CentOS 7

Working with pcs

Adding cluster resources, constraints, and resource groups

Managing resources

Removing cluster constraints, resource groups, and resources

Summary

11. Playing with Cluster Nodes on CentOS 7

11. Playing with Cluster Nodes on CentOS 7

Adding a new cluster node

Cluster node standby mode

Removing a cluster node

Summary

12. STONITH on CentOS 7

12. STONITH on CentOS 7

Fencing

Configuring fence devices

IPMI management board fencing

HP iLO management board fencing

Fence test

Summary

13. Testing Failover on CentOS 7

13. Testing Failover on CentOS 7

Hardware failure

Network failure

Summary

14. Two-node Cluster Considerations on CentOS 7

14. Two-node Cluster Considerations on CentOS 7

Quorum in a two-node cluster

Two-node cluster configuration

Summary

Index

Index

Removing cluster constraints, resource groups, and resources

Knowing how to remove the configured cluster constraints, resource groups, and resources is just as important as knowing how to configure them. Removing them is quite easy and self-explanatory.

Removing resource constraints

You can see the configured cluster resource constraints with the following command:

pcs constraint show

In the following screenshot, you can see the output of the pcs constraint show command.

As you can see in the preceding screenshot, the possible configured location constraints are:

Location constraints: None configured
Ordering constraints: The cluster resource order constraint is set to start the resource called ClusterIP before the resource called WebServer
Colocation constraints: The cluster resource colocation constraint is configured to run resources ClusterIP and WebServer together
You can delete the cluster order constraint from the preceding example with the following command:
```
pcs constraint order remove...
```

Visually different images

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