RHCSA: How to use Red Hat as a virtual machine host

This is part 5 of the learning Red Hat series on my blog. If you use RHEL 7 or RHEL 8, did you know that you can use it as a virtual machine host – straight out of the box. This works on Centos 7 / 8 as well.

RHEL7/8 can be used as a virtual machine host.

There are a number of prerequistes needed to create a VM host.

First you need to check your CPU supports virtualization

 grep -E '(vmx|svm)' /proc/cpuinfo 

If this returns a value your CPU is compatable, if this command returns nothing then your CPU doesnt support Virtual Instructions. Note that you may need to enable this feature on your system BIOS – look for VT-x or AMD-V

The following system software is needed – here are the Pre-reqs:

• qemu-kvm
• python-virtinst
• libvirt
• libvirt-python
• virt-manager
• libguestfs-tools
• virt-install
• qemu-img
• Libvirt-client

These can be installed using yum. Here is the command you need:

redhat/centos

yum install qemu-kvm python-virtinst libvirt libvirt-python virt-manager libguestfs-tools virt-install qemu-img Libvirt-client -y

Enable Libvertd daemon

Systemctl enable libvirtd

Systemctl start libvirtd

Next you will need to configure the network

echo "net.ipv4.ip_forward = 1" | tee /etc/sysctl.conf# sysctl -p 

Running Virt Manager in the GUI

Virtual Machine manager is a GUI application, using GNOME is the easiest way to get it working, otherwise you will need to configure X11 forwarding on your putty session.

Type Virt-install command line

virt-install \
 --name centos7 \
 --ram 1024 \
 --disk
 path=/path/to/disk.qcow2,size=8 \
 --vcpus 1 \
 --os-type linux \
 --network bridge=virbr0 \
 --location /path/to/linux.iso \
 --extra-args 'console=ttyS0’
 

The above code will create a centos7 server with 1GB ram, 1 CPU and 8GB Hard disk

Running Virt Manager on the command line

You can use the virsh command to manually edit virtual machines.

• help
• list
• dumpxml
• start
• Destroy    [STOP]
• reboot
• suspend / resume
• Undefine   [DELETE]
• autostart

Virtual Machines dont start by default 

Its important to note that virsh does not start VMs automatically by default.

Here are some useful commands to work around this:

Virsh autostart servername

[email protected] ~]# virsh list –all

 Id    Name                           State

—————————————————-

 –     centos7.0                      shut off

 –     centos7.0-3                    shut off –     generic                        shut off
—
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