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.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.
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
Create needed directories:
# mkdir -p /data01/vm-storage # mkdir /data01/iso-images
Make the virsh pool configuration changes:
# 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/.
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.