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KVM

Here are the steps needed to get KVM up and running.

EL7

  1. Install dependencies

    sudo yum install -y kvm virt-manager libvirt virt-install qemu-kvm libvirt-client virt-viewer bridge-utils

  2. Enable IPv4 forwarding

    echo "net.ipv4.ip_forward = 1"|sudo tee /etc/sysctl.d/99-ipforward.conf net.ipv4.ip_forward = 1
sudo sysctl -p /etc/sysctl.d/99-ipforward.conf net.ipv4.ip_forward = 1

  3. Fix netowrk script for your ethernet device. This example will presume eno1 is your network device. Edit /etc/sysconfig/network-scripts/ifcfg-eno1 and remove anything that doesn't fit this example (we do not need any IPv4/IPv6 data here, just the HWADDR (MAC address) and the basic on-boot information.

    DEVICE="eno1"
NAME="Onboard Ethernet"
ONBOOT=yes
HWADDR="00:0c:29:32:d0:4c"
BRIDGE=br0

  4. Create bridge device. This is a new file we will create at /etc/sysconfig/network-scripts/ifcfg-br0. Edit the IPADDR, NETMASK, GATEWAY, and DNS lines to use a separate subnet to what you are using:

    DEVICE="br0"
NAME="Ethernet Bridge"
TYPE=BRIDGE
ONBOOT=yes
BOOTPROTO=static
IPADDR="10.0.0.2"
NETMASK="255.0.0.0"
GATEWAY="10.0.0.1"
DNS1="10.0.0.1"

  5. For dynamic IPs in your guests, setup KVM to use bridged networking or setup your bridge as follows:

    DEVICE=br0
NAME="Ethernet Bridge"
TYPE=Bridge
BOOTPROTO=dhcp
ONBOOT=yes
DELAY=0

  6. Add user(s) to libvirt group to manage VMs

    sudo gpasswd libvirt -a USERNAME

  7. Reboot to enable changes.

    sudo systemctl reboot

RHEL 8+, FEDORA

  1. Install dependencies

    sudo dnf groupinstall "Virtualization"
sudo dnf install qemu-img  libvirt libvirt-python libvirt-client

  2. Add user(s) to libvirt group to manage VMs

    sudo gpasswd libvirt -a USERNAME

  3. Reboot to enable changes

    sudo systemctl reboot

UBUNTU

  1. Install dependencies

    sudo apt install -y qemu-kvm libvirt0 libvirt-bin virt-manager bridge-utils

  2. Enable service

    sudo systemctl enable libvirtd

  3. Enable bridge (presuming ethernet adapter is eno1, change as needed)

    cat <<EOF | sudo tee /etc/network/interfaces
auto lo
iface lo inet loopback
auto br0
iface br0 inet dhcp
      bridge_ports eno1
      bridge_stp off
      bridge_maxwait 0
EOF

  4. Reboot to have settings take effect

    sudo reboot

USE NETWORK MANAGER CLI (nmcli)

  1. I personally move/vape the existing /etc/sysconfig/network-scripts/ifcfg-* and use nmcli to start fresh, just in case something isnt overwritten correctly. But to each their own.

  2. Install needed packages

  3. CREATE BRIDGE

    nmcli con add type bridge con-name br0 ifname br0 autoconnect yes

  4. ADD $ADAPTER TO BRIDGE

    nmcli con add type ethernet con-name $ADAPTER ifname $ADAPTER master br0 autoconnect yes
nmcli con mod br0 bridge.stp no

  5. USE STATIC IP ON BRIDGE

    nmcli con mod br0 ipv4.addresses 192.168.1.2/16 ipv4.method manual ipv4.gateway 192.168.1.1 ipv4.dns  8.8.8.8

  6. USE DHCP ON BRIDGE

    nmcli con mod br0 ipv4.method auto

USE NETWORK-MANAGER AS USER

  1. Create a new group:

    newgrp libvirt

  2. Add the selected user to group

    sudo usermod -a -G libvirt $USER

  3. Edit /etc/libvirt/libvirtd.conf and change the following parameters to match:

    unix_sock_group = "libvirt"
unix_sock_rw_perms = "0770"

  4. Restart daemon

    sudo systemctl restart libvirtd.service

REFERENCES