KVM Host Setup

From Newroco Tech Docs
Revision as of 07:51, 10 May 2023 by Emilian.mitocariu (talk | contribs)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigationJump to search

Ubuntu 20.04 and newer

Install packages

apt install qemu qemu-kvm libvirt-daemon-system libvirt-clients bridge-utils vlan virtinst libguestfs-tools

For the rest follow steps from Ubuntu 18.04 section

Ubuntu 18.04

Install packages

apt install qemu qemu-kvm libvirt-bin bridge-utils vlan virtinst libguestfs-tools


If you need interface level vlan support do

sudo modprobe 8021q

Edit /etc/netplan/01-netcfg.yaml

# This file describes the network interfaces available on your system
# For more information, see netplan(5).
  version: 2
  renderer: networkd
    eno1:            ###this can be named something else on other servers, check the available interface(s) with "ip addr" command
      dhcp4: no
      dhcp6: no

      id: 98
      link: eno1

      interfaces: [eno1]
      addresses: [ ]
        addresses: []
        stp: false
        forward-delay: 9
        hello-time: 2
        max-age: 12
      interfaces: [eno1.98]
      dhcp4: no
      dhcp6: no
        stp: false
        forward-delay: 9
        hello-time: 2
        max-age: 12

If needed, a bond can be configured like this:

      interfaces: [eno1,enp3s0f1]
      dhcp4: no
      dhcp6: no
        mii-monitor-interval: 100
        mode: 802.3ad
        down-delay: 200
        up-delay: 200
        lacp-rate: fast

If you are using bonds, you need to change the config above and make the relevant bridge/vlan use the bond instead of an interface.

Netplan doesn't bring UP interfaces that do not have an IP address (extbr98 bridge for example), so we need to create a simple configuration file to force this. Note: this might be fixed in the future so worth checking at a later time.

Note: this doesn't seem to be needed in Ubuntu 20.04 anymore

#vi /etc/systemd/network/extbr98.network



Apply the changes

netplan apply

Zabbix Monitoring

For zabbix to be able to monitor if VMs have autostart, we need to do the following steps when building a new KVM host.

NOTE: after installing zabbix-agent

Add zabbix user to libvirt group

adduser zabbix libvirt

Add the following lines at the end of file /etc/zabbix/zabbix_agentd.conf

UserParameter=vm.running.discovery,l=$(virsh -c qemu:///system list | grep running | awk '{print $2}');echo -n '{"data":[';for i in ${l};do echo -n "{\"{#VMNAME}\": \"$i\"},";done|sed -e 's:\},$:\}:';echo -n ']}';
UserParameter=vm.running.check.autostart[*],virsh -c qemu:///system list --all --autostart | grep running | awk '{print $ 2}' | grep -Fxq $1 && echo 1 || echo 0
UserParameter=vm.shutdown.discovery,l=$(virsh -c qemu:///system list --all | grep "shut off" | awk '{print $2}');echo -n '{"data":[';for i in ${l};do echo -n "{\"{#VMNAME}\": \"$i\"},";done|sed -e 's:\},$:\}:';echo -n ']}';
UserParameter=vm.shutdown.check.autostart[*],virsh -c qemu:///system list --all --autostart | grep "shut off" | awk '{print $ 2}' | grep -Fxq $1 && echo 1 || echo 0

Restart the zabbix agent

systemctl restart zabbix-agent

Building VMs

For how to build a VM visit this page: Cloud-Init

Ubuntu 16.04 or older

Basic install

If your machine was built with a package set to support virtualisation this step may not be necessary.

apt-get install kvm libvirt-bin bridge-utils vlan python-vm-builder libguestfs-tools


If need interface level vlan support do

 sudo modprobe 8021q

We use bridging for the network interfaces. There can be several interfaces: e.g. a "main" interface, one for a storage network and/or dedicated connection, one for guests on an SSN. Adapt IP addressing and interface definitions as necessary. Different setups will have very different requirements.

  • Edit /etc/network/interfaces as needed, bridging interfaces to suit:
 # Main interface
 auto br0
 iface br0 inet static
 bridge_ports eth0   [CHECK what your particular interface is called - it may be eth0, but may be em1 for instance]
 bridge_fd 9
 bridge_hello 2
 bridge_maxage 12
 bridge_stp off

 # SAN
 auto br1
 iface br1 inet static
 bridge_ports eth1
 bridge_fd 9
 bridge_hello 2
 bridge_maxage 12
 bridge_stp off

 # SSN
 auto eth0.98
 iface eth0.98 inet manual

 auto extbr98
 iface extbr98 inet manual
 bridge_ports eth0.98
 bridge_fd 9
 bridge_hello 2
 bridge_maxage 12
 bridge_stp off

The interfaces should have the same name on all hosts, so that we can move VMs from one host to the other without having to change the configuration every time.

Modifying default virtual bridge

By default libvirt creates a virtual bridge named virbr0 (can be checked with ifconfig command). If you want to modify this interface for another subnet you can do this by first shutting down the interface:

virsh net-destroy default

Modify the interface

virsh net-edit default

And start it again

virsh net-start default
Mods for vmbuilder on 16.04 (awaiting fork) - DEPRECATED

If you run into an error from dpkg, related to the script giving the wrong response to a "should I overwrite this conf file" question, edit the related Python lib and rerun:

vi /usr/lib/python2.7/dist-packages/VMBuilder/plugins/ubuntu/dapper.py

Find the line containing "dist-upgrade" and change "-y" to "-s" (changing the command to test mode only)

self.run_in_target('apt-get', '-s', '--force-yes', 'dist-upgrade',


self.install_from_template('/etc/sudoers', 'sudoers')

If building 16.04 VMs as normal, you should modify the template file to use the new style Ethernet device naming:

vi /etc/vmbuilder/ubuntu/interfaces.tmpl

and change every instance of eth0 to ens3 (assumes no other changes - as the interfaces now named in order of enumeration, so an additional PCI device could change which is the one associated with a network device. Simpler, in general, to build the basic machine, gain access to it via SSH and modify it and its hardware definition from that point on.

Use the following line to create a new 16.04 VM on a 16.04 host, modifying as necessary to suit your network environment etc.:

vmbuilder kvm ubuntu --libvirt qemu:///system --debug -v --tmpfs=1280 --bridge=br0 --arch=amd64 --suite=xenial --flavour=virtual --mirror='http://gb.archive.ubuntu.com/ubuntu/' --components=main --rootpass=<yourinitialrootpass> -d /var/lib/libvirt/images/<machinename> -m 1024 --cpus=2 --rootsize=9182 --swapsize=4096 --hostname=<machinename> --ip=ip.add.re.ss --mask= --gw=gateway.ip.add.ress --dns=internal.dns.ser.ver --addpkg=vim --addpkg=openssh-server --addpkg=curl --addpkg=linux-image-generic

Note you cannot create a newer VM on an older host i.e. to create a 16.04 you must build on a 16.04 host. You can build older releases on a later host, and in general an older host will work with any compatible VM regardless of installed OS.

See also