kvm2

Linux KVM (Kernel-based Virtual Machine) driver

Overview

KVM (Kernel-based Virtual Machine) is a full virtualization solution for Linux on x86 hardware containing virtualization extensions. To work with KVM, minikube uses the libvirt virtualization API

Requirements

  • libvirt v1.3.1 or higher
  • qemu-kvm v2.0 or higher

Installing Prerequisites

Proper installation of KVM and libvirt is highly specific to each Linux distribution. Please consult:

Once configured, validate that libvirt reports no errors:

virt-host-validate

Usage

Start a cluster using the kvm2 driver:

minikube start --driver=kvm2

To make kvm2 the default driver:

minikube config set driver kvm2

Check virtualization support

To use VM drivers, verify that your system has virtualization support enabled:

egrep -q 'vmx|svm' /proc/cpuinfo && echo yes || echo no

If the above command outputs “no”:

  • If you are running within a VM, your hypervisor does not allow nested virtualization. You will need to use the None (bare-metal) driver
  • If you are running on a physical machine, ensure that your BIOS has hardware virtualization enabled

Special features

The minikube start command supports 5 additional KVM specific flags:

  • --gpu: Enable experimental NVIDIA GPU support in minikube
  • --hidden: Hide the hypervisor signature from the guest in minikube
  • --kvm-network: The KVM default network name
  • --network: The dedicated KVM private network name
  • --kvm-qemu-uri: The KVM qemu uri, defaults to qemu:///system

Issues

  • minikube will repeatedly ask for the root password if user is not in the correct libvirt group #3467
  • Machine didn't return an IP after 120 seconds when firewall prevents VM network access #3566
  • unable to set user and group to '65534:992 when dynamic ownership = 1 in qemu.conf #4467
  • KVM VM’s cannot be used simultaneously with VirtualBox #4913
  • On some distributions, libvirt bridge networking may fail until the host reboots

Also see co/kvm2 open issues

Nested Virtulization

If you are running KVM in a nested virtualization environment ensure your config the kernel modules correctly follow either this or this tutorial.

Troubleshooting

  • Run id to confirm that user belongs to the libvirt[d] group (the output should contain entry similar to: ‘groups=…,108(libvirt),…').
  • Run virsh domcapabilities --virttype="kvm" to confirm that the host supports KVM virtualisation.
  • Run virt-host-validate and check for the suggestions.
  • Run ls -la `which virsh` , virsh uri, sudo virsh net-list --all and ip a s to collect additional information for debugging.
  • Run minikube start --alsologtostderr -v=9 to debug crashes.
  • Run docker-machine-driver-kvm2 version to verify the kvm2 driver executes properly.
  • Read How to debug Virtualization problems

Troubleshooting KVM/libvirt networks

For the most part, minikube will try to detect and resolve any issues with the KVM/libvirt networks for you. However, there are some situations where manual intervention is needed, mostly because root privileges are required.

  1. Run sudo virsh net-list --all to list all interfaces.

example output:

 Name                     State    Autostart   Persistent
-----------------------------------------------------------
 default                  active   yes         yes
 mk-kvm0                  active   yes         yes
 mk-minikube              active   yes         yes
 my-custom-kvm-priv-net   active   yes         yes

where:

  • default is the default libvirt network,
  • mk-kvm0 is a default libvirt network created for minikube kvm0 profile (eg, using minikube start -p kvm0 --driver=kvm2),
  • mk-minikube is a network created for default minikube profile (eg, using minikube start --driver=kvm2) and
  • my-custom-kvm-priv-net is a custom private network name provided for minikube profile (eg, using minikube start -p kvm1 --driver=kvm2 --network="my-custom-kvm-priv-net").
  1. Run sudo virsh net-autostart <network> to manually set network to autostart, if not already set.

  2. Run sudo virsh net-start <network> to manually start/activate network, if not already started/active.

    1. In case that the default libvirt network is missing or is unable to start/activate - consult your OS/distro-specific libvirt docs; the following steps might help you to fix the issue:

      1. Run sudo virsh net-dumpxml default > default.xml to backup the default libvirt network config.
      2. Run sudo virsh net-destroy default to stop the default libvirt network.
      3. Run sudo virsh net-undefine default to delete the default libvirt network.
      4. Run sudo virsh net-define /usr/share/libvirt/networks/default.xml to recreate the default libvirt network.
        • Note: repeat above steps b. and c. and then Run sudo virsh net-define default.xml to restore the original default libvirt network config, in case of any issue.
      5. Run sudo virsh net-start default to start the default libvirt network.
      6. Run sudo virsh net-autostart default to autostart the default libvirt network.
    2. If non-default libvirt network is unable to start/activate, use the following steps:

      1. Run sudo virsh net-dumpxml <network> to dump XML network config - note the bridge name=<bridge> and ip address='<address>' netmask='<netmask>' values. Example output:
      <network connections='1'>
        <name>mk-minikube</name>
        <uuid>cfcb37fb-fd75-4599-825a-14bee5d863f5</uuid>
        <bridge name='virbr1' stp='on' delay='0'/>
        <mac address='52:54:00:80:97:5a'/>
        <dns enable='no'/>
        <ip address='192.168.39.1' netmask='255.255.255.0'>
          <dhcp>
            <range start='192.168.39.2' end='192.168.39.254'/>
          </dhcp>
        </ip>
      </network>
      

      b. Run ip -4 -br -o a s to show all interfaces with assigned IPs (in CIDR format), now compare the above IP address and netmask with those of the bridge. Example output:

      lo               UNKNOWN        127.0.0.1/8
      virbr0           UP             192.168.122.1/24
      wlp113s0         UP             192.168.42.17/24
      br-08ada8d5dfa4  DOWN           172.22.0.1/16
      docker0          DOWN           172.17.0.1/16
      virbr1           UP             192.168.39.1/24
      
      • IF THEY MATCH, or THE IP ADDRESS ISN’T LISTED ANYWHERE: Run sudo ip link delete <bridge> followed by sudo virsh net-start <network> and sudo virsh net-autostart <network> to let libvirt recreate the bridge and [auto]start the network.
      • IF THE IP ADDRESS BELONGS TO ANOTHER INTERFACE: something else occupied the IP address creating the conflict, and you’ll have to determine what and then choose between the two…
  3. Run sudo systemctl restart libvirtd or sudo systemctl restart libvirt (depending on your OS/distro) to restart the libvirt daemon.

Hopefully, by now you have libvirt network operational, and you will be successfully running minikube again.

Last modified March 28, 2021: kvm2 driver: update website (4e34b3547)