QEMU

QEMU

Prerequisite

Required packages

You have to install qemu, qemu-utils packages.

lstlisting caption= Install packages ,style=bash

sudo apt install qemu qemu-utils

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lstlisting caption= Install packages for MacOS ,style=bash

brew install qemu

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Create a virtual strogae device

lstlisting caption= Create a qcow2 image ,style=bash

sudo qemu-img create -f qcow2 ubuntu.img 20G

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Mount the qcow2 image on your host machine

lstlisting caption= Load the NBD kernel module ,style=bash

modprobe nbd max_part=8

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Connect to the qcow2 as a network block device

lstlisting caption= Connect to the NBD ,style=bash

qemu-nbd --connect=/dev/nbd0 /var/lib/vz/images/100/vm-100-disk-1.qcow2

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Mount the network block device as a type of the loop device

lstlisting caption= Mount the NBD ,style=bash

mount /dev/nbd0p2 /mnt/loop

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Clean up the NBD configurations

lstlisting caption= Clean up the NBD ,style=bash

umount /mnt/loop

qemu-nbd --disconnect /dev/nbd0

rmmod nbd

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Shrink the qcow2 image file size

After creating the image file, we can shrink the image size for saving storage space. shrinkqemuimg

lstlisting caption= Shrink the qcow2 image file ,style=bash

qemu-img convert -O qcow2 source.qcow2 shrunk.qcow2

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Download an image file of the Ubuntu server ISO

Find an image file of ubuntu server from https://releases.ubuntu.com

(example, http://releases.ubuntu.com/18.04.3/ubuntu-18.04.3-live-server-amd64.iso? _ga=2.209385489.209752045.1576807893-1215086369.1576225824 -O ubuntu-18.04.3-live-server-amd64.iso)

Boot up VM instance with downloaded Ubuntu image file

lstlisting caption= Boot a VM instance from the CD ,style=bash

sudo qemu-system-x86_64 -hda ubuntu.img -enable-kvm -boot d -cdrom ubuntu-18.04.3-live-server-amd64.iso -m 1g

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lstlisting caption= Boot a VM instance from the CD - macOS ,style=bash

sudo qemu-system-x86_64 -hda ubuntu.img -accel hvf -boot d -cdrom ubuntu-18.04.3-live-server-amd64.iso -m 1g

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Boot up VM instance

In order to install the kubernetes mastr node, a VM instance should be created with at least 2 CPUs.

lstlisting caption= Boot a VM instance ,style=bash

qemu-system-x86_64 -hda ubuntu.img -device e1000,netdev=net0,mac=de:ad:be:ef:00:00 -netdev tap,id=net0 -enable-kvm -m 1g -cpu host -serial mon:stdio -smp 2 -nographic

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Setting up a console and a monitor path for the VM instance

In order to manage the VM instance efficiently, we should prepare a virtual (serial) console and a QEMU monitor path.

The QEMU qemudoc provide several methods for them. qemusocket

First, the kernel image and initramfs image should be accessible from the host system. The QEMU will start boot from those files.

After the kernel boot is done, the VM OS will mount a root device using a qcow2 image file given with -hda option of the qemu-system-x86 _64 command. (/home/vm/link-local.img)

lstlisting caption= Unix Domain Socket ,style=bash

qemu-system-x86_64 -hda /home/vm/link-local.img -kernel "/home/vm/boot/vmlinuz" -initrd "/home/vm/boot/initrd.img" -append "root=UUID=d1fe778d-f6f2-4f03-88e4-047359b532ed ro maybe-ubiquity console=ttyS0,115200n8" -device e1000,netdev=net0,mac=be:ee:be:ee:00:00 -netdev tap,id=net0 -enable-kvm -m 1g -cpu host -smp 2 -nographic -chardev socket,id=monitor,path=/home/vm/run/link-local.monitor.sock,server,nowait -monitor chardev:monitor -chardev socket,id=serial0,path=/home/vm/run/link-local.console.sock,server,nowait -serial chardev:serial0

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lstlisting caption= Network setting for MacOS ,style=bash

sudo qemu-system-x86_64 -hda ubuntu.img -nic vmnet-bridged,ifname=en0 -accel hvf -m 1g

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After the VM instance is activated, you can attach minicom to it.

lstlisting caption= Minicom to socket ,style=bash

minicom -D unix #/tmp/.qemu_link-local.console.sock

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Network configuration

When you launch a new VM instance, the script /etc/qmeu-ifup will be invoked automatically.

Therefore, we can configure network interfaces for the new VM instance.

caption= /etc/qemu-ifup ,style=bash examples/qemu/qemu-ifup

Also the /etc/qemu-ifdown script will be invoked when the VM instance is terminated.

caption= /etc/qemu-ifdown ,style=bash examples/qemu/qemu-ifdown

We will create a bridge interface first and then create a new tap device.

After creating a tap device, let the tap join into the created bridge interface.

First of all, we should set the name of the bridge interface.

Here, in this project, we will use a "br _" as a prefix of the name of the bridge device.

And we will get the last name from parsing a given name of a tap device.

The script will receive the name of the tap device with a numbered suffix. Therefore we can parse the prefix of the name of a tap device.

You would need to know interface type to make decision for whether add a new bridge interface or not netbridge .

TUN/TAP

Q. How to know if a network interface is tap, tun, bridge or physical?

A. tuntap: /sys/class/net/ NAME /tun _flags

bridge: /sys/class/net/ NAME /bridge

bridges and lo: /sys/class/net/ NAME /address is 00:00:00:00:00:00

physical: /sys/class/net/ NAME /device symlink

findiftype

In order to give a permission to create tun/tap device to qemu, you should set valid permission for it. getcap

caption= Change permissions ,style=bash examples/qemu/setcap.cmd

Register the VM as a systemd service

First you should create a systemd service script.

caption= Service file ,style=bash examples/qemu/qemu@.service

The important thing is suffix of a filename AT('@') sign.

The systemd service gets option from command line after the AT('@') sign.

begin lstlisting caption= Command Line ,style=bash

systemctl start qemu@master

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The "master" string following after AT('@') sign would replace a " %i" string in the service file.

You are able to set the hostname of each VM instance via kernel command line (boot parameters).

It is supported by systemd v246.

You are able to set the hostname using "systemd.hostname" option.

In order to send the MAC address as for each VM instance's dhcp-client-id,

The /etc/dhcp/dhclient.conf file should be updated.

lstlisting caption= DHCP Client Id ,style=bash

send dhcp-client-identifier hardware;

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In the most case, we use the systemd-networkd.

Then we should change the /etc/systemd/networkd.conf file.

lstlisting caption= networkd.conf ,style=bash

...

DHCP

ClientIdentifier=mac

DUIDType=link-layer-time

...

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kvmnetworking

netplanbr

tunctl

ipcmd

netbridge