Skip to content

Latest commit

 

History

History
160 lines (104 loc) · 4.34 KB

Manual.md

File metadata and controls

160 lines (104 loc) · 4.34 KB

Manual

In manual part we are going to see two base example of using QEMU in order to virtualize our system.

1. VM Creation

In first example we are going to create a virtual machine on our system using QEMU.

create directory

Before creating a directory to make drives, download an operating system iso image. You can use Ubuntu, Alpine, Bullseye, etc.

mkdir Ubuntu-VM
sudo mv /path/to/ubuntu.iso ./Ubuntu-VM

create image file

Now create an image file in order to boot qemu from it.

cd Ubuntu-VM
qemu-img create -f qcow2 Image.img 20G

The above command will create a virtual disk image file that's 20GB in size. The virtual machine will use this disk image to store data, so make sure to specify a size accordingly.

start vm

Next, run the following command to start the Ubuntu virtual machine:

qemu-system-x86_64 -enable-kvm -cdrom ubuntu.iso -boot menu=on -drive file=Image.img -m 4G -cpu host -vga virtio -display sdl,gl=on

The virtual machine window will pop up. Press Escape to open the boot menu and select the appropriate option to boot from the ISO file.

restart vm

After installing Ubuntu, make sure you remove the -cdrom flag from the qemu command. This will boot Ubuntu from the disk image file rather than the ISO file.

qemu-system-x86_64 -enable-kvm -boot menu=on -drive file=Image.img -m 4G -cpu host -vga virtio -display sdl,gl=on

2. Hosting QEMU VMs with Public IP Addresses using TAP Interfaces

To allow VMs to have their own IP addresses while using the same physical link, we need to introduce a bridge into this setup. Both the VM’s network interface as well as the host’s interface will be connected to the bridge.

create bridge

ip link add br0 type bridge
ip link set br0 up

Next, we want to connect the eth0 interface to the bridge and re-assign the IP address from eth0 to br0. Please note that these commands will drop internet connectivity of your machine, so either only run them on a local PC or ensure that in case of disaster you can reboot the machine somehow. 192.168.0.10 is just an example IP address, you need to use your own of course.

add ip to bridge

ip link set eth0 up
ip link set eth0 master br0

ip addr flush dev eth0

ip addr add 192.168.0.10/24 brd + dev br0
ip route add default via 192.168.0.1 dev br0

tap interface

Next, we can create the TAP interface to be used by the VMs. $YOUR_USER is used to allow an unprivileged user to connect to the TAP device. This is important for QEMU, since QEMU VMs should be started as non-root users.

ip tuntap add dev tap0 mode tap user $YOUR_USER
ip link set dev tap0 up
ip link set tap0 master br0

start

And now we can start a VM. The MAC address could e.g. be generated randomly:

RAND_MAC=$(printf 'DE:AD:BE:EF:%02X:%02X\n' $((RANDOM%256)) $((RANDOM%256)))

qemu-system-x86_64 -m 1024 -cdrom archlinux-2020.05.01-x86_64.iso \
   -device virtio-net-pci,netdev=network0,mac=$RAND_MAC \
   -netdev tap,id=network0,ifname=tap0,script=no,downscript=no

3. CPU Hotplugin

Run qmp-shell (located in the source tree, under ‍‍‍‍/scripts/qmp/) to connect to the just-launched QEMU:

./qmp-shell -p -v /tmp/qmp-sock

Find out which CPU types could be plugged, and into which sockets:

query-hotpluggable-cpus

The query-hotpluggable-cpus command returns an object for CPUs that are present (containing a qom-path member).

adding a new vCPU

From its output, we can see that IvyBridge-IBRS-x86_64-cpu is present in socket 1, while hot-plugging a CPU into socket 1 requires passing the listed properties to QMP device_add:

device_add id=cpu-2 driver=IvyBridge-IBRS-x86_64-cpu socket-id=0 core-id=1 thread-id=0

Question 1

What is driver in this command? 
Cpu model type name.
In here it is IvyBridge-IBRS-x86_64-cpu.

Optionally, run QMP query-cpus-fast for some details about the vCPUs:

query-cpus-fast

removing vCPU

From the qmp-shell, invoke the QMP device_del command:

device_del id=cpu-2

Resources