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Requirements OVZ7:
CPU: at least 4 cores, a 64-bit processor is required for running 64-bit guest operating systems,
• RAM: 4 GB or more,
• HDD: 64 GB or more,
• SSD (optional): at least 30 GB (at least 32 GB with /boot)

When partitioning the disks, keep in mind that OpenVZ requires these partitions:
• Boot: mount point /boot, 1 GB, boot partition with OpenVZ boot files, created on each HDD,
• Root: mount point /, 12-24 GB, root partition with OpenVZ files, created on the HDD marked System,

• Swap: paging partition with the swap file system, created on the HDD marked System. The size depends on RAM:
• if RAM is below 2 GB, swap size should be twice the RAM,
• if RAM is 2-8 GB, swap size should be equal to RAM,
• if RAM is 8-64 GB, swap size should be half the RAM,
otherwise swap size should be 32 GB

• Data storage, mount point /vz, at least 30 GB, storage for virtual machines, containers, and OS and
application templates, an LVM volume group that spans all HDDs marked Datastore.
• In addition, either a 1 MB partition with the BIOS boot file system or a 200 MB partition with the EFI
boot file system is required depending on your server configuration.

Source requirements: https://docs.openvz.org/openvz_users_guide.pdf

Lets start!
Install OVZ7 on Hetzner Dedicated Servers.

Step 1: Start installimage in Rescue Mode
Step 2: Partition requirements (EXT4!):
(/swap )- 50% (32GB = 16GB SWAP) 
(/boot) - 1GB (EXT4)
(/) - 40GB (EXT4)
(/vz) - All unused space for ex. (EXT4)

Step 3: Image https://www.tomvanbrienen.nl/ovz7-hetzner/CentOS-70-64-minimal.tar
# Info: The CentOS-70-64-minimal.tar is a clean installation tar from the original openvz-iso-7.0.7-361.iso. Factory/test repos are disabled.
# URL: https://download.openvz.org/virtuozzo/releases/7.0/x86_64/iso/

Step 4: F2 & F10 to start the installation.
Step 5: When the installation is finished, reboot and login with your root account and rescue password.
Step 6: Important: cd /root
Step 7: Download the networkconfigurator: wget https://www.tomvanbrienen.nl/ovz7-hetzner/networkconfig-ovz7.zip
Step 8: Unzip the files: unzip networkconfig-ovz7.zip
Step 9: Execute permissions: chmod +x network.sh
Step 10: Run network.sh: ./network.sh
Step 11: nano /etc/sysconfig/network-scripts/ifcfg-br0 and check the network configuration! 
Step 12: nano /etc/sysconfig/network-scripts/ifcfg-eth0 and check the network configuration!
Step 13: Type: service network restart to apply your new config.

Check https://www.tomvanbrienen.nl/category/openvz/ for more information about OpenVZ.

Attachments:
Example ifcfg-br0:
DEVICE="br0"
ONBOOT=yes
NETBOOT=yes
IPV6INIT=yes
BOOTPROTO=none
PROXY_METHOD=none
BROWSER_ONLY=no
PREFIX=27
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
IPV6_PRIVACY=no
TYPE="Bridge"
DELAY="2"
STP="off"
IPADDR=1.1.1.1
GATEWAY=1.1.1.255
DNS1=x.x.98.98
DNS2=x.x.99.99
DNS3=x.x.100.100
UUID="NEW UUID"

Example ifcfg-eth0:
NAME="eth0"
DEVICE="eth0"
ONBOOT=yes
TYPE=Ethernet
BRIDGE="br0"
UUID="NEW UUID"