linuxexpert-practice-labs/labs/linux-plus/1-7-1-kvm-and-qemu

Linux+ 1.7.1: KVM, QEMU and virtual disks

Getting a host ready for KVM, and working with disk images: qcow2 and raw, resizing, converting, and a backing file.

Before you start

Task 1 is best done on a VM with nested virtualization (the CPU flag vmx or svm inside it), but nothing here runs a VM, so the lab works without it too: virt-host-validate then reports what's missing. The images go in /tmp, which Ubuntu empties at boot, so do task 2 without a reboot. Task 3 asks for a finding: write it to /root/lab-answers/3. Reset removes the packages task 1 installs, if they weren't there before.

Tasks

1. Check the host for KVM support, install QEMU, qemu-img, libvirt and virt-install, and run virt-host-validate qemu.
2. Create a 5 GiB qcow2 image /tmp/a.qcow2 and grow it by 1 GiB. Convert it to a raw image, /tmp/a.raw, and compare the space each really uses. Then create /tmp/b.qcow2, a qcow2 image with /tmp/a.qcow2 as its backing file, and look at the backing chain.
3. Check whether this VM uses VirtIO devices. Write the driver of its main network interface, as ethtool -i reports it, to /root/lab-answers/3.

Hints

• grep -cE 'vmx|svm' /proc/cpuinfo, lsmod | grep kvm, ls -l /dev/kvm.
• RHEL family: qemu-kvm qemu-img libvirt virt-install. Ubuntu: qemu-system-x86 qemu-utils libvirt-daemon-system virtinst.
• qemu-img create -f qcow2, qemu-img info, qemu-img resize +1G, qemu-img convert -f qcow2 -O raw, ls -ls, qemu-img create -f qcow2 -F qcow2 -b BACKING NEW, qemu-img info --backing-chain.
• lspci | grep -i virtio; ip route shows the main interface.