RHEL7: Configure a physical machine to host virtual guests.

Note: This is an RHCSA 7 exam objective.

Prerequisites

Download the CentOS 7 distribution (see Software requirements) and install it with default configuration.

Choose a domain name (example.com strongly recommended), a host name (for example master.example.com) and an IP address compatible with your network environment (here 192.168.1.5, gateway is supposed to be 192.168.1.1).

Update your system:

# yum update

Installation Procedure

Install the KVM packages:

# yum group install "Virtualization Host"
# yum install -y virt-install virt-top libguestfs-tools

Note: The libguestfs-tools brings the very useful virt-sparsify command with it. When space is sparse, this command is invaluable: it limits the virtual machine footprint to the space used only.

Start the libvirtd service:

# systemctl start libvirtd

Activate the Chronyd/NTP service at boot and start it:

# systemctl enable chronyd && systemctl start chronyd

Check the installation:

# virt-host-validate
QEMU: Checking for hardware virtualization : PASS
QEMU: Checking for device /dev/kvm : PASS
QEMU: Checking for device /dev/vhost-net : PASS
QEMU: Checking for device /dev/net/tun : PASS
LXC: Checking for Linux >= 2.6.26 : PASS

To get optimal performances, activate the virtual-host tuned profile:

# tuned-adm profile virtual-host

KVM Tip

You have just installed a KVM host but this installation will only last for 1 year. After this period and a reboot, your KVM certificate will expire. Look at this tutorial about KVM certificate expiration to set up an installation for more than 1 year.

KVM Updates

If you need a more recent version of QEMU/KVM (Nvidia GPU driver, etc), you can do it through a dedicated repository.

Install the EPEL repository:

# yum -y install epel-release

Install the CentOS-QEMU-EV repository:

# yum -y install centos-release-qemu-ev

Install the qemu-kvm-ev package:

# yum -y install qemu-kvm-ev

Restart the libvirtd daemon:

# systemctl restart libvirtd

Check the QEMU/KVM version:

# /usr/libexec/qemu-kvm -version
QEMU emulator version 2.12.0 (qemu-kvm-ev-2.12.0-18.el7_6.1.1)
Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers

Display the various supported models:

# /usr/libexec/qemu-kvm -machine help
Supported machines are:
pc RHEL 7.6.0 PC (i440FX + PIIX, 1996) (alias of pc-i440fx-rhel7.6.0)
pc-i440fx-rhel7.6.0 RHEL 7.6.0 PC (i440FX + PIIX, 1996) (default)
pc-i440fx-rhel7.5.0 RHEL 7.5.0 PC (i440FX + PIIX, 1996)
pc-i440fx-rhel7.4.0 RHEL 7.4.0 PC (i440FX + PIIX, 1996)
pc-i440fx-rhel7.3.0 RHEL 7.3.0 PC (i440FX + PIIX, 1996)
pc-i440fx-rhel7.2.0 RHEL 7.2.0 PC (i440FX + PIIX, 1996)
pc-i440fx-rhel7.1.0 RHEL 7.1.0 PC (i440FX + PIIX, 1996)
pc-i440fx-rhel7.0.0 RHEL 7.0.0 PC (i440FX + PIIX, 1996)
rhel6.6.0 RHEL 6.6.0 PC
rhel6.5.0 RHEL 6.5.0 PC
rhel6.4.0 RHEL 6.4.0 PC
rhel6.3.0 RHEL 6.3.0 PC
rhel6.2.0 RHEL 6.2.0 PC
rhel6.1.0 RHEL 6.1.0 PC
rhel6.0.0 RHEL 6.0.0 PC
q35 RHEL-7.6.0 PC (Q35 + ICH9, 2009) (alias of pc-q35-rhel7.6.0)
pc-q35-rhel7.6.0 RHEL-7.6.0 PC (Q35 + ICH9, 2009)
pc-q35-rhel7.5.0 RHEL-7.5.0 PC (Q35 + ICH9, 2009)
pc-q35-rhel7.4.0 RHEL-7.4.0 PC (Q35 + ICH9, 2009)
pc-q35-rhel7.3.0 RHEL-7.3.0 PC (Q35 + ICH9, 2009)
none empty machine

Source: www.server-world.info.

Additional Resources

You can get this QEMU error message: “qemu-kvm: Failed to create chardev”. In this case, follow the solution here.