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Red Hat Enterprise Linux Server Cookbook

You're reading from   Red Hat Enterprise Linux Server Cookbook Over 60 recipes to help you build, configure, and orchestrate RHEL 7 Server to make your everyday administration experience seamless

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Product type Paperback
Published in Dec 2015
Publisher
ISBN-13 9781784392017
Length 250 pages
Edition 1st Edition
Tools
Concepts
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Authors (2):
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Jakub Gaj Jakub Gaj
Author Profile Icon Jakub Gaj
Jakub Gaj
William Leemans William Leemans
Author Profile Icon William Leemans
William Leemans
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Toc

Table of Contents (12) Chapters Close

Preface 1. Working with KVM Guests FREE CHAPTER 2. Deploying RHEL "En Masse" 3. Configuring Your Network 4. Configuring Your New System 5. Using SELinux 6. Orchestrating with Ansible 7. Puppet Configuration Management 8. Yum and Repositories 9. Securing RHEL 7 10. Monitoring and Performance Tuning Index

Adding RAM on the fly

As with CPUs, the possibility to add memory on the fly is an added value in mission-critical environments where downtime can literally cost a company millions of Euros.

The recipe presented here is quite simple, similar to the one on CPUs. Here, your guest needs to be prepared to use this functionality as well.

Getting ready

If you want to be able to add memory on the fly to a guest, it must be configured to support it. As with the CPU, this has to be activated. There are three ways to do this:

  • The guest must be created with the maxmem option, as follows:
    --memory 2G,maxmemory=4G
  • You can set the maximum memory using the virsh command, as follows:
    ~]# virsh setmaxmem --domain <guestname> --size <max mem> --live
    
  • You can edit the guests' XML files:
    ~]# virsh edit <guestname>
    

Of course, the latter 2 option requires you to shut down the guest, which is not always possible in production environments.

Ensure that the guests' XML configuration files contain the following elements with the subsequent attributes:

<domain type='kvm'>
...
    <memory unit='KiB'>4194304</memory>
    <currentMemory unit='KiB'>2097152</currentMemory>
...
</domain>

How to do it…

Let's increase the guest's memory.

On the KVM host, perform the following steps:

  1. Get the current and maximum memory allocation for a guest, as follows:
    ~]# virsh dumpxml srv00002 |grep -i memory
      <memory unit='KiB'>4194304</memory>
      <currentMemory unit='KiB'>4194304</currentMemory>
    
  2. Set the new amount of memory for the guest by executing the following command:
    ~]# virsh setmem --domain <guestname> --size <memory> --live
    

On the KVM guest, perform the following:

  1. Tell your guest OS about the memory increase through this command:
    ~]# for i in $(grep -H offline /sys/devices/system/memory/memory*/state | awk -F: '{print $1}'); do echo online > $i; done
    
You have been reading a chapter from
Red Hat Enterprise Linux Server Cookbook
Published in: Dec 2015
Publisher:
ISBN-13: 9781784392017
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