# Pre-Installation Preparation ## Assumptions Omnia assumes that prior to installation: * The manager and compute nodes must be installed with CentOS 7.9 2009 OS. * Network(s) has been cabled and nodes can reach the Internet. * SSH Keys for root have been installed on all nodes to allow for password-less SSH. * On the manager node, install Ansible and Git using the following commands: * `yum install epel-release -y` * `yum install ansible git -y` __Note:__ Ansible must be installed using __yum__. If Ansible is installed using __pip3__, re-install it using the __yum__ command again. ## Example system designs Omnia can configure systems which use Ethernet- or Infiniband-based fabric to connect the compute servers.   ## Network Setup Omnia assumes that servers are already connected to the network and have access to the internet. ### Network Topology Possible network configurations include: * A flat topology where all nodes are connected to a switch which includes an uplink to the internet. This requires multiple externally-facing IP addresses * A hierarchical topology where compute nodes are connected to a common switch, but the manager node contains a second network connection which is connected to the internet. All outbound/inbound traffic would be routed through the manager node. This requires setting up firewall rules for IP masquerade, see [here](https://www.server-world.info/en/note?os=CentOS_7&p=firewalld&f=2) for an example. ### IP and Hostname Assignment The recommended setup is to assign IP addresses to individual servers. This can be done manually by logging onto each node, or via DHCP.