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Instructions for Setting Up a CentOS 7 System with Bridged Networking for Virtual Machines

bgstack15

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CentOS 7 bridging network card for virtual machines

My goal is to set up virtualization where the guests can access the entire LAN as well as the host over the network. The host should also be able to reach all the guests via the network. This task was so simple, but somehow it eluded me for over a year. I use this document to establish a new kvm host in my network pool.

Install virtualization tools

sudo yum -y install libvirt qemu-kvm virt-install
sudo systemctl enable libvirtd.service ; sudo systemctl start libvirtd.service
sudo setsebool -P virt_use_nfs 1

Adjust the ethernet configuration

sudo su -
{
this_nic="$( nmcli device show | awk '/^GENERAL.DEVICE:/ && $2 ~ /e.*/ {print $2}' )"
indir=/etc/sysconfig/network-scripts
this_bridge=br0
this_nic_count="$( printf "%s\n" "${this_nic}" | sed '/^\s*$/d' | wc -l )"
if test ${this_nic_count} -ne 1 ;
then
   echo "Other than 1 nic detected. Please deal with manually. Aborted."
else
   # prepare values for bridge definition
   this_mac="$( ip -o link | grep "${this_nic}" | grep -oE 'ether [a-fA-F0-9:]{17}' | awk '{print $2}' | tr '[[:lower:]]' '[[:upper:]]' )"
   this_ipaddr="$( ip -o address show "${this_nic}" | grep -oE 'inet [0-9\.]{7,15}' | awk '{print $2}' )"
   # define bridge interface
   {
      echo "DEVICE=${this_bridge}"
      echo "TYPE=Bridge"
      echo "ONBOOT=yes"
      echo "DELAY=0"
      grep -h -E 'DNS1|DNS2|DOMAIN|IPADDR|PREFIX|BOOTPROTO|GATEWAY|DEFROUTE' "${indir}/ifcfg-${this_nic}"
   } > "${indir}/ifcfg-${this_bridge}"
   # define ethernet card
   old_nic_file="${indir}/ifcfg-${this_nic}"
   temp_nic_file="${indir}/ifcfg-${this_nic}-new"
   {
      echo "DEVICE=${this_nic}"
      echo "HWADDR=${this_mac}"
      echo "ONBOOT=yes"
      echo "BRIDGE=${this_bridge}"
      grep -h -E 'UUID' "${old_nic_file}"
   } > "${temp_nic_file}"
   chmod --reference "${old_nic_file}" "${temp_nic_file}"
   /bin/mv -f "${temp_nic_file}" "${old_nic_file}"
fi
}

systemctl restart network.service NetworkManager.service

Using the virtual host

With the setup complete, the environment is ready to serve virtual machines!

Install a virtual machine

vm=c7-03a ; time sudo virt-install -n "${vm}" --memory 2048 --vcpus=1 --os-variant=centos7.0 --accelerate -v --disk path=/var/lib/libvirt/images/"${vm}".qcow2,size=20 -l /mnt/public/Support/SetupsBig/Linux/CentOS-7-x86_64-Minimal-1804.iso --initrd-inject=/mnt/public/Support/Platforms/CentOS7/centos7-ks.cfg --extra-args "ks=file:/centos7-ks.cfg SERVERNAME=${vm} NOTIFYEMAIL=bgstack15@ipa.example.com" --debug --network type=bridge,source=br0 --noautoconsole

Delete a virtual machine

vm=c7-03a; sudo virsh destroy "${vm}"; sudo virsh undefine --remove-all-storage "${vm}";

References

Weblinks

  1. https://wiki.libvirt.org/page/Networking

Internal files

  1. file:///mnt/public/Support/Platforms/CentOS7/centos7-ks.cfg

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