Virtual Machine (KVM)

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Revision as of 17:57, 23 December 2018 by Sstrutt (talk | contribs) (Added Auto Start)
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Note that VMs are known as domains in the KVM world.

Prerequisites

This guide assumes you have a basic working environment, run the kvm-ok command to sanity check...

root@kvm-host:# kvm-ok
INFO: /dev/kvm exists
KVM acceleration can be used

Install Media

You need to have a local copy of the appropriate ISO. If you have the ISO file already, upload to your KVM server, alternatively download from the site using wget

Create Virtual Machine

Parameter Example Usage
name VM-Name Name of virtual machine (typically this should match the intended hostname of the VM)
description "Test VM to be used for X" Description of virtual machine's purpose etc
os-type Linux OS family, can be Linux, Solaris, Unix or Windows
os-variant ubuntu16.04 Distribution type for the above (run osinfo-query os to view what is available)
ram 2048 vRAM in GB
vcpus 2 vCPUs (cores)
vcpus 2 vCPUs (cores)
disk path /vm-store/images/VM-Name.img,bus=virtio,size=50 Virtual disk path, using virtio bus and with a 50GB disk
graphics none If noneset, VM will be created with a serial display output (as opposed to VNC window)
cdrom /home/user/cdrom.iso Path to installation ISO
network bridge:br0 Network connection details

Create Server (no GUI)

Update paths to reflect where install ISO, and where VM disk files are intended to be.

The --extra-args "console=ttyS0" option allows a local console to be accessed from the host machine (to allow OS install etc before the VM is on a network), though note that it can't be used with --cdrom, so --location has been used instead.

virt-install \
--virt-type=kvm \
--name server-name \
--ram 1024 \
--vcpus=1 \
--os-variant=ubuntu16.04 \
--network=bridge=br0,model=virtio \
--graphics none \
--disk path=/mnt/md0/kvm/vm/server-name.img,size=20,bus=virtio \
--extra-args "console=ttyS0" \
--location /mnt/md0/kvm/iso/ubuntu-16.04.3-server-amd64.iso

You should be presented with the console of the VM as it installs, however if you lose connection etc, connect to the console of the server using virsh console <server-name>. Make sure you set a static IP and install SSH during setup (select OpenSSH server during Software selection section). Once installation is completed, SSH to the server and setup normal console access (as the instructions in the section below). Its highly recommended that you follow the steps below to ensure that Console access is available via the KVM host if needed.

Console Access

  1. Update the /etc/default/grub
  2. Add console=ttyS0 to the config line GRUB_CMDLINE_LINUX_DEFAULT
    • EG GRUB_CMDLINE_LINUX_DEFAULT="quiet splash console=ttyS0"
  3. Update grub
    • update-grub
  4. Restart the guest machine

Connect using virsh console <server-name>, you may need to hit Return once to show the logon prompt.

Create Workstation (GUI)

virt-install \
--virt-type=kvm \
--name ubuntu-desktop \
--ram 2048 \
--vcpus=1 \
--os-variant=ubuntu16.04 \
--cdrom=/mnt/md0/kvm/iso/ubuntu-16.04.3-desktop-amd64.iso \
--network=bridge=br0,model=virtio \
--graphics vnc \
--disk path=/mnt/md0/kvm/vm/ubuntu-desktop.img,size=40,bus=virtio

Once the command has got as far as Waiting for installation to complete. you need to connect to the VNC console session, to find the port number to connect on query the config from anothet SSH session connected to the host (typically VNC uses ports starting from 5900 upwards).

 virsh dumpxml ubuntu-desktop | grep vnc

Other Config

Auto Start

To ensure that a VM domain starts with the host server issue the following commands (replace vm-name with the name of your VM

virsh autostart vm-name

To disable issue

virsh autostart vm-name --disable