KVM Hypervisor on Red Hat / CentOS 8.x
KVM is an open source hardware virtualization solution which can be used to run several Linux-based or Windows-based systems in parallel on one host.
KVM is known as a so-called “Kernel based Virtual Machine”. This is because after installing the package, the KVM module is loaded with the kernel at the next boot, turning a normal Linux server into a bare metal hypervisor.
Now I will describe how to set up such a KVM Hypervisor and how to manage it afterwards.
Before we start, verify support for Virtual Technology of the CPU by issueing the following command:
# lscpu | grep Virtualization
Virtualization: VT-x Virtualization type: full
The output of the above command shows that, our server kvm-virtualization-01.recipes.com supports Virtualization.
However, if the above command returns no result on your server then,
In case of bare-metal machine, you have to enable the VT support from system BIOS.In case of virtual machine, you have to enable the VT support from VM's CPU Settings.
Installing KVM and QEMU
In CentOS 8 / RHEL 8, virtualization components including KVM and QEMU hypervisors are bundled in virt module. Therefore, it is really simple now to configure a KVM virtualization host in CentOS 8.
We are installing virt module using dnf command.
# dnf install -y @virt
... ================================================================================ Installed: libguestfs-1:1.38.4-11.1.module_el8.0.0+189+f9babebb.x86_64 libvirt-client-4.5.0-24.3.module_el8.0.0+189+f9babebb.x86_64 libvirt-daemon-config-network-4.5.0-24.3.module_el8.0.0+189+f9babebb.x86_64 libvirt-daemon-kvm-4.5.0-24.3.module_el8.0.0+189+f9babebb.x86_64 alsa-lib-1.1.6-3.el8.x86_64 autogen-libopts-5.18.12-7.el8.x86_64 boost-atomic-1.66.0-6.el8.x86_64 boost-chrono-1.66.0-6.el8.x86_64 boost-date-time-1.66.0-6.el8.x86_64 boost-iostreams-1.66.0-6.el8.x86_64 boost-program-options-1.66.0-6.el8.x86_64 boost-random-1.66.0-6.el8.x86_64 boost-regex-1.66.0-6.el8.x86_64 boost-system-1.66.0-6.el8.x86_64 boost-thread-1.66.0-6.el8.x86_64 cairo-1.15.12-3.el8.x86_64 celt051-0.5.1.3-15.el8.x86_64 dnsmasq-2.79-4.el8.x86_64 edk2-ovmf-20180508gitee3198e672e2-9.el8_0.1.noarch fribidi-1.0.4-6.el8.x86_64 genisoimage-1.1.11-39.el8.x86_64 glusterfs-api-3.12.2-40.2.el8.x86_64 glusterfs-cli-3.12.2-40.2.el8.x86_64 gnutls-dane-3.6.5-2.el8.x86_64 gnutls-utils-3.6.5-2.el8.x86_64 graphite2-1.3.10-10.el8.x86_64 gstreamer1-1.14.0-3.el8.x86_64 gstreamer1-plugins-base-1.14.0-4.el8.x86_64 harfbuzz-1.7.5-3.el8.x86_64 hivex-1.3.15-7.module_el8.0.0+189+f9babebb.x86_64 ipxe-roms-qemu-20181214-1.git133f4c47.el8.noarch iso-codes-3.79-2.el8.noarch libX11-1.6.7-1.el8.x86_64 libX11-common-1.6.7-1.el8.noarch libX11-xcb-1.6.7-1.el8.x86_64 libXau-1.0.8-13.el8.x86_64 ...
We are also installing virt-install package, because it provides some very useful command line tools.
# dnf install -y virt-install
... ================================================================================ Installing: virt-install noarch 2.0.0-5.1.el8 AppStream 100 k Installing dependencies: libosinfo x86_64 1.2.0-5.el8 AppStream 244 k osinfo-db noarch 20181011-8.el8_0.1 AppStream 172 k osinfo-db-tools x86_64 1.2.0-1.el8 AppStream 90 k python3-libvirt x86_64 4.5.0-2.module_el8.0.0+189+f9babebb AppStream 291 k virt-manager-common noarch 2.0.0-5.1.el8 AppStream 921 k python3-chardet noarch 3.0.4-7.el8 BaseOS 195 k python3-pysocks noarch 1.6.8-3.el8 BaseOS 34 k python3-requests noarch 2.20.0-1.el8 BaseOS 123 k python3-urllib3 noarch 1.23-5.el8 BaseOS 178 k Transaction Summary ================================================================================ Install 10 Packages ...
Validate all the components on your KVM host can support virtualization.
# virt-host-validate
QEMU: Checking for hardware virtualization : PASS QEMU: Checking if device /dev/kvm exists : PASS QEMU: Checking if device /dev/kvm is accessible : PASS QEMU: Checking if device /dev/vhost-net exists : PASS QEMU: Checking if device /dev/net/tun exists : PASS QEMU: Checking for cgroup 'memory' controller support : PASS QEMU: Checking for cgroup 'memory' controller mount-point : PASS QEMU: Checking for cgroup 'cpu' controller support : PASS QEMU: Checking for cgroup 'cpu' controller mount-point : PASS QEMU: Checking for cgroup 'cpuacct' controller support : PASS QEMU: Checking for cgroup 'cpuacct' controller mount-point : PASS QEMU: Checking for cgroup 'cpuset' controller support : PASS QEMU: Checking for cgroup 'cpuset' controller mount-point : PASS QEMU: Checking for cgroup 'devices' controller support : PASS QEMU: Checking for cgroup 'devices' controller mount-point : PASS QEMU: Checking for cgroup 'blkio' controller support : PASS QEMU: Checking for cgroup 'blkio' controller mount-point : PASS QEMU: Checking for device assignment IOMMU support : PASS QEMU: Checking if IOMMU is enabled by kernel : WARN (IOMMU appears to be disabled in kernel. Add intel_iommu=on to kernel cmdline arguments)
It looks like IOMMU (input-output memory management unit) support is not yet enabled in the CentOS 8 Kernel.
The solution is already suggested by the above command. Therefore, we are adding the same in the Kernel command line options.
# grub2-editenv - set "$(grub2-editenv - list | grep kernelopts) intel_iommu=on"
To take effect, restart your machine!
After reboot, again run the virt-host-validate command.
QEMU: Checking for hardware virtualization : PASS QEMU: Checking if device /dev/kvm exists : PASS QEMU: Checking if device /dev/kvm is accessible : PASS QEMU: Checking if device /dev/vhost-net exists : PASS QEMU: Checking if device /dev/net/tun exists : PASS QEMU: Checking for cgroup 'memory' controller support : PASS QEMU: Checking for cgroup 'memory' controller mount-point : PASS QEMU: Checking for cgroup 'cpu' controller support : PASS QEMU: Checking for cgroup 'cpu' controller mount-point : PASS QEMU: Checking for cgroup 'cpuacct' controller support : PASS QEMU: Checking for cgroup 'cpuacct' controller mount-point : PASS QEMU: Checking for cgroup 'cpuset' controller support : PASS QEMU: Checking for cgroup 'cpuset' controller mount-point : PASS QEMU: Checking for cgroup 'devices' controller support : PASS QEMU: Checking for cgroup 'devices' controller mount-point : PASS QEMU: Checking for cgroup 'blkio' controller support : PASS QEMU: Checking for cgroup 'blkio' controller mount-point : PASS QEMU: Checking for device assignment IOMMU support : PASS QEMU: Checking if IOMMU is enabled by kernel : PASS
Everything is fine now.
KVM and QEMU hypervisors has been installed on CentOS 8.
Configure KVM Environment
Allow QEMU/KVM Commands for personal user:
If you want to allow your login user (non-root) to run virsh command or other KVM/QEMU commands, or use these commands without sudo, (needed by cockpit) then add your login user to the libvirt group as follows:
# usermod -aG libvirt YOURUSERNAME
Setup own VM-Storage / ISO-Storage configuration:
Create needed directories:
# mkdir -p /data01/vm-storage # mkdir /data01/iso-images
Make the virsh pool configuration changes:
- Listing current pools:
# virsh pool-list
Name State Autostart ------------------------------------------- default active yes
Destroying current default pool:# virsh pool-destroy default
Pool default destroyed
Undefine current default pool:# virsh pool-undefine default
Pool default has been undefined
Defining a new pool with name “default”:# virsh pool-define-as --name default --type dir --target /data01/vm-storage
Pool default defined
Set pool to be started when libvirt daemons starts:# virsh pool-autostart default
Pool default marked as autostarted
Start pool:# virsh pool-start default
Pool default started
Checking pool state:# virsh pool-list
Name State Autostart ------------------------------------------- default active yes
From now, when creating virtual machines, Virtual Machine Manager will inform you that the *.img file (virtual disk of your VM), will be saved at /data01/vm-storage/.
Installing Cockpit Web Interface in CentOS 8
Although, KVM commandline-tools are quite sufficient for managing a Virtualization environment. But, we can also use the CentOS 8 native Web UI i.e. Cockpit to manage virtual machines via a graphical interface.
We are installing Cockpit using dnf command. To add support of managing virtual machines, we have to install cockpit-machines package as well.
# dnf install -y cockpit cockpit-machines
... ================================================================================ Installing: cockpit x86_64 185.1-1.el8_0 BaseOS 68 k cockpit-machines noarch 184.1-1.el8 AppStream 669 k Installing dependencies: PackageKit x86_64 1.1.12-2.el8 AppStream 600 k PackageKit-glib x86_64 1.1.12-2.el8 AppStream 141 k cairo-gobject x86_64 1.15.12-3.el8 AppStream 33 k python3-cairo x86_64 1.16.3-6.el8 AppStream 90 k python3-gobject x86_64 3.28.3-1.el8 AppStream 25 k python3-systemd x86_64 234-8.el8 AppStream 81 k setroubleshoot-plugins noarch 3.3.10-1.el8 AppStream 365 k checkpolicy x86_64 2.8-2.el8 BaseOS 338 k cockpit-bridge x86_64 185.1-1.el8_0 BaseOS 596 k cockpit-system noarch 185.1-1.el8_0 BaseOS 1.6 M cockpit-ws x86_64 185.1-1.el8_0 BaseOS 834 k gdk-pixbuf2 x86_64 2.36.12-2.el8 BaseOS 466 k glib-networking x86_64 2.56.1-1.1.el8 BaseOS 155 k gsettings-desktop-schemas x86_64 3.28.1-1.el8 BaseOS 619 k ...
Enable and start Cockpit Unit.
# systemctl enable --now cockpit.socket
Created symlink /etc/systemd/system/sockets.target.wants/cockpit.socket at /usr/lib/systemd/system/cockpit.socket
Cockpit service is by-default allowed in CentOS 8 firewall.
Browse URL https://YOUR-SERVERS-IP:9090/ in a client's browser.
The Cockpit uses a self-signed SSL certificate, therefore, you may see a Security warning. Ignore the Security warning and continue to the website.