Difference between revisions of "Qemu"

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(Moved paragraph about qxl from the XFCE page to here, because it is more relevant here.)
 
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{{:Running Alpine Linux As a QEMU networked Guest}}
 
{{:Running Alpine Linux As a QEMU networked Guest}}
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= Using Xorg inside Qemu =
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The video driver needed for Xorg inside Qemu is <code>xf86-video-modesetting</code>.
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If you decided to use a ''qxl'' Video on KVM/Qemu guest, add this configuration to `/etc/X11/xorg.conf`
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{{Cmd|Section "Device"
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  Identifier "qxl"
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  Driver "qxl"
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  Option "ENABLE_SURFACES" "False"
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EndSection}}
  
 
= Run a guest OS on Alpine Linux using Qemu =
 
= Run a guest OS on Alpine Linux using Qemu =
{{:Run_Guest_in_Alpine}}
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{{Cmd|sudo apk add qemu-system-x86_64 qemu-ui-gtk}}
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{{Cmd|sudo modprobe kvm-intel}}
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{{Cmd|sudo addgroup user kvm}}
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Logout and login again so you become part of the kvm group
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{{Cmd|qemu-system-x86_64 --enable-kvm -m 1024M -fda M6410220.IMG}}
  
 
[[Category:Virtualization]]
 
[[Category:Virtualization]]

Latest revision as of 04:02, 2 May 2020

QEMU is a very flexible open source machine emulator and virtualizer. QEMU is able to virtualize x86, PowerPC, and S390 guests.

Install Alpine Linux in Qemu

Before You Start

  • Download the latest Alpine image.
  • Install QEMU on your system (e.g. sudo apt install qemu on Ubuntu, yum -y install qemu on Fedora)

Create the Virtual Machine

Create a disk image if you want to install Alpine Linux.

qemu-img create -f qcow2 alpine.qcow2 8G

The following command starts QEMU with the Alpine ISO image as CDROM, the default network configuration, 512MB RAM, the disk image that was created in the previous step, and CDROM as the boot device.

qemu-system-x86_64 -m 512 -nic user -boot d -cdrom alpine-standard-3.10.2-x86_64.iso -hda alpine.qcow2

Tip: Add option -enable-kvm if your hardware support this.

Log in as root (no password) and run:

setup-alpine

Follow the setup-alpine installation steps.

Use poweroff to shut down the machine.

Booting the Virtual Machine

After the installation QEMU can be started from disk image (-boot c) without CDROM.

qemu-system-x86_64 -m 512 -nic user -hda alpine.qcow2

Live mode

To just give Alpine Linux a try in diskless mode, qemu can be used to boot the .iso file without any need for a virtual HDD image or further configuration.

qemu -m 512 -cdrom alpine-3.2.0-x86_64.iso

Issue

grsec nomodeset

at boot prompt to avoid being forced into graphical mode and losing access.

Letting the .iso image load an apkovl

This works by mounting a persitent filesytem under /media and selecting it to store the apkovl and the apkcache.

Preparing a KVM with a virtual drive:

mkdir -p /media/usb/images
qemu-img create -f raw /media/usb/images/mykvm.config 32M
qemu-system-x86_64 -enable-kvm -m 384 \
-name mykvm \
-cdrom /media/usb/images/alpine-3.2.0-x86_64.iso \
-drive file=/media/usb/images/mykvm.config,if=virtio \ 
-net lan \
-boot d &

And inside the KVM (running alpine linux):

fdisk /dev/vda  #creating a partition
mkdosfs /dev/vda1
mkdir -p /media/vda1
echo "/dev/vda1 /media/vda1 vfat rw 0 0" >> /etc/fstab
mount -a
setup-alpine  # (select vda1 for saving configs)
lbu commit

The next reboot then loads the generated apkovl and apkcache found on /dev/vda1 -- completely running-from-ram based on the latest official ISO.

Advanced network configuration

To get networking running correctly, you can use the tun/tap interface, which then becomes a real interface. The key is to define the virtual network interface on the correct virtual vlan, and the correct ifup script.

You need 2 net commands on the command line interface, one for the host:

-net tap,vlan=[somenumber],ifname=[host if],script=[some script]

one for the guest

-net nic,vlan=[samenumber]

So to have a single NIC on the qemu virtual system that is connected to tap0 on the physical host:

qemu -net tap,vlan=0,ifname=tap0,script=./qemu-ifup -net nic,vlan0 \
    -boot d -cdrom alpine*.iso}}


To create a qemu guest with more than one nic, just repeat the -net commands

qemu -net tap,vlan=0,ifname=tap0,script=./qemu-ifup -net nic,vlan0 \
      -net tap,vlan=0,ifname=tap1,script=./qemu-ifup -net nic,vlan0 \
      -net tap,vlan=0,ifname=tap2,script=./qemu-ifup -net nic,vlan0 \
      -boot d -cdrom alpine*.iso}}

Now your alpine guest will have 3 NICs, mapped to tap0, tap1, and tap2 respectively.

What's actually happening is you are effectively creating a point-to-point tunnel, with the phys tap0 device being one endpoint, and the virtual box's eth0 being on the other point of the tunnel.

So you need to assign ip addresses to BOTH sides of the tunnel. The qemu-ifup script is what does that for the host. Here's an example:

#!/bin/sh
case $1 in
      tun0 | tap0 )
              sudo /sbin/ip addr add 192.168.1.100/24 dev $1
              sudo /sbin/ip link set $1 up
              ;;
      tap1 | tun1 )
              sudo /sbin/ip addr add 192.168.2.100/24 dev $1
              sudo /sbin/ip link set $1 up
              ;;
      tap2 | tun2 )
              sudo /sbin/ip addr add 192.168.3.100/24 dev $1
              sudo /sbin/ip link set $1 up
              ;;
      esac

In your alpinebox, create an interfaces file like this:

iface eth0 inet static
      address 192.168.1.1
      netmask 255.255.255.0
      gateway 192.168.1.100

iface eth1 inet static
      address 192.168.2.1
      netmask 255.255.255.0

iface eth0 inet static
      address 192.168.3.1
      netmask 255.255.255.0

If on your host you now add a MASQUERADE rule for tap0 to your host's default nic, and you turn on ip_forward on your host, you can now do svn updates, surf, run tranmission, etc right from your qemu guest.

Using Xorg inside Qemu

The video driver needed for Xorg inside Qemu is xf86-video-modesetting.

If you decided to use a qxl Video on KVM/Qemu guest, add this configuration to `/etc/X11/xorg.conf`

Section "Device" Identifier "qxl" Driver "qxl" Option "ENABLE_SURFACES" "False" EndSection

Run a guest OS on Alpine Linux using Qemu

sudo apk add qemu-system-x86_64 qemu-ui-gtk

sudo modprobe kvm-intel

sudo addgroup user kvm

Logout and login again so you become part of the kvm group

qemu-system-x86_64 --enable-kvm -m 1024M -fda M6410220.IMG