2.7. Preparing to Run Digital Rebar

2.7.1. Overview

This document describes several considerations and preparation for a successful setup and test (Proof-of-Concept, PoC, Trial, Test, etc.) of the Digital Rebar Platform (DRP). This document applies to both test environment setups, and preparing for a production installation.

2.7.2. Sizing Your Endpoint

Generally speaking, DRP by itself does not require many resources from either your physical or virtual machines. However, there are several considerations primarily around the following, roughly in order of importance:

  • CPU
  • Memory
  • I/O (disk and network)
  • Network Throughput
  • Disk Space

For basic setup and testing of small scale environments (below 100 phyiscal or virtual machines), the following minimum resources should be sufficient (more is always better):

  • 2x (v)CPU at 2.0 GHz or better
  • 4 GByte (v)Memory
  • 100 GByte - this may vary dramatically if provisiong Windows Images
  • Prefer SSD class storage
  • 1 gbps (v)NIC

For a more complete discussion on Endpoint sizing within production environments, please refer to the Endpoint Sizing, Performance and Scaling Guide.

Please realize that provisiong can have extremely complex performance differences depending on the type of provisioning (kickstart, preseed, image deployments), size of artifacts, concurrency or parallel builds, and other external infrastructure that your Workflows integrate with. If you have any questions or would like guidance, please contact RackN for help.

2.7.3. Supported Operating Systems

DRP is a single binary Golang application, which can be compiled and run on a number of different operating systems and hardware platform architectures. However, there are several environmental considerations and constraints that the service relies on. As a consequcne, the following is the Operating System support information:

2.7.3.1. Linux Distributions

The following notes apply to Linux.

  • Typically any modern Linux distro should work
  • Only 64 bit OS builds are currently compiled, tested, and supported
  • Most testing is performed on CentOS 7, CentOS 8, RHEL 8, Ubuntu 18.04
  • Intel/AMD (x86_64, amd64) and ARM architectures are supported
  • RaspberryPI (rPI) is supported with custom named rpi builds

Most of RackN’s commercial customers use either CentOS/RHEL, Ubuntu, or a Docker container.

2.7.3.2. MacOS X (Darwin)

DRP runs and is regularly tested on MacOS X. However, RackN does not recommend nor support DRP running in production environments on MacOS X.

2.7.3.3. Container Environments

DRP is released on Docker Hub as new releases are made. This allows DRP to run on any supported environment that runs Docker Containers. Other container environments may also work, but are not actively tested by RackN.

Note

For container environments, you will need to ensure you map low numbered ports in to the container correctly, and provide elevated privileges for the container that DRP is running in.

The RackN release docker container supports storing all writable data in a separate storage volume that is attached to the container. The install.sh script provides installation, upgrade, and removeal support for containers; incluiding the storage volume.

Please see the Production Install documentation for more complete details.

2.7.3.4. Miscellaneous Notes

DRP may run on other alternative platforms that are loosely similar to Linux. For example, the BSD variants. However, RackN does not test nor support these distributions today.

2.7.3.5. Windows

RackN does not support, nor does the dr-provision (DRP Endpoint) service run on Windows. The Command Line tool (drpcli) does run, and is supported fully on Windows 64 bit operating system versions.

2.7.4. Network Connectivity

2.7.4.1. DHCP Broadcast Traffic

DRP provides PXE boot provisioning and DHCP IP addressing for systems. As such, your DRP Endpoint will need network connectivity via the locally connected network interfaces, and routing to any of the network subnets that you wish to provide Provisioning services for. As long as standard IP connectivity and reachability can be accomplished, DRP should be able to successfully provision systems.

If DRP is the IP Address Management (IPAM) service for your systems via the built-in DHCP server, you must also ensure IP Helpers or DHCP Relay options on your network switches/routers are correctly set up to forward Broadcast DHCP traffic to the DRP Endpoint IP address. This is a standard requirement for any DHCP and PXE provisioning system, and is not unique to DRP.

Some additional resources related to forwarding DHCP traffic appropriately:

IP Helper / DHCP Relay issues must be addressed both in Physical environments and Virtual Environments. Ultimately, your switch (be it virtual or physical) must forward Broadcast DHCP traffic to the DRP Endpoint.

2.7.4.2. Interface Speed and Duplex

DRP’s communication to support Workflow does not require much bandwith. Generally, these control messages are small packets, and do not consume much network resources. However, the act of provisioning systems will require bandwidth dependent on the number of systems being provisioned in parallel, and the size of the provisioning artifacts (packages, images, etc). If these resources are hosted on the DRP Endpoints web service (the standard configuration), then you will need to consider these activities in your sizing.

For small lab and test environments, a single 1 gbps full duplex network link is likely sufficient. For larger production environments, we recommend 2x 10 gbps bonded links for both bandwidth, and reliability.

Please refer to the Endpoint Sizing, Performance and Scaling Guide for additional information.

2.7.4.3. Provisioning -vs- Baseboard Management Network

The Baseboard Management Network (BMC), often times referred to inaccurately as the “IPMI” network, provides out-of-band control path and management of the physical machines in your environment. Typically these networks are isolated from production network traffic. DRP can be configured to interact with, and control physical machine hardware via the BMC. The only requirement that DRP has, it network reachability to the IP addresses of the BMC systems themselves.

To accompllish this, the DRP Endpoint can be “multi-homed”, or connected via NICs/Network Segments to both the in-band provisioning network, and the out-of-band provisioning network. Alternatively, a single network interface will suffice, if that network routes to the BMC interfaces. In this case, it would be prudent to insure that Firewall or ACL rules block access to unknown systems. If firewall/ACLs are in place, ensure that your DRP Endpoint(s) IP addresses are whitelisted/allowewd access.

2.7.4.4. Multiple Network Connections

It is not necessary to add multiple network interfaces on the DRP endpoint to each network, assuming that the network switches and/or routers are appropriately forwarding DHCP Broadcast traffic to the DRP Endpoint.

If you do have multiple network connections on the DRP endpoint, it is absolutely critical that you evaluate your networks Layer 3 (routed) topology, and ensure there are not asymmetric routing issues. If a packet ingresses one interface, but the DRP Endpoints operating system routing rules forward replies out a different interface, this will almost always break provisioning services.

You may need to install/use IP Policy Based Routing (PBR) rules on the DRP Endpoint host operating system to insure inbound/outbound routing of traffic conforms correctly to the required network paths. For additional information, and resources, see:

2.7.5. DHCP Services / IP Addressing

The DRP Endpoint services is also a full fledges DHCP server. DRP works extremely hard to provide clean, fast, and accurate DHCP services that are tightly integrated with the Provisioniong process. The service is also designed to reduce as much complexity as possible in the setup, operation, and runtime of the DHCP services. Generally speaking, we encourage and recommend that customers use the DRP based DCHP services whenever possible.

However, in environments with existing (legacy) based DHCP services, or with very complex network topologies or hardware, it may not be possible to use DRP’s DHCP services. DRP provisioning does support use of external DHCP services. The basic mechanisms of “nextserver” and “bootfile” configurations must be setup correctly in the external DHCP server. That configuration is generally extremely specific to the hardware and the DHCP server implementation. Please consult your documentation on how to forward the DHCP PXE traffic appropriately.

DRP controls it’s internal DHCP services via the definition of Subnets which define the start and ending ranges for IP Address handout during the DHCP negotiations (often times referred to as DORA). The DHCP server will NOT interfer with other DHCP traffic, as long as a Subnet for that Layer 3 network is not configured.

Ultimately - there can only be ONE authoritative DHCP server of record for a Layer 3 Subnet/Network. You must ensure that there are no other competing DHCP servers or services on the network, otherwise provisioning activities will likely fail.

DRP does support providing Proxy DHCP responses for limited DHCP servers that do not understand how to provide the PXE required nextserver and bootfile.

2.7.6. Provisioning Targets (Machines) Requirements

2.7.6.1. Physical Machine Requirements

The vast majority of physical hardware that is provisioned and managed with DRP are server class systems, with a Baseboard Management Controller (BMC, iDRAC, iLO, XCC, etc.). Typically, you will want to set these systems in BIOS to boot PXE first on the primary NIC that you designate as your in-band provisioning network. Systems with a BMC are not required, as long as they can be set to PXE boot, in those cases, DRP can take control via the PXE boot path, and in-band reboots of the system. External power control will have to be used/implemented outside of DRP in these cases (contact RackN, there are tools to control other non-standard Power Management systems).

DRP is capable of managing switches (via ONIE/ZTP boot/install control), and storage devices. For these devices, please contact RackN for further details.

2.7.6.2. Using Virtual Machines

DRP will provision Virtual Machines equally well as physical hardware. Similar to physical hardware, the Virtual Machine vBIOS boot order needs to be configured with PXE boot first.

If you are utilizing virtual machines, you are generally free to size your VMs to whatever virtual hardware sizes you need. However, note that some Operating Systems that you might provision will have requirements that may dictate the lower bounds of your VMs sizing configuration.

For example, CentOS/Redhat VMs should be configured with at least 2 GB of vMemory. This is a requirement of the CentOS installation and dracut tooling. In general, we would recommend not configuring vMemory on your Virtual Machines with less than 2 GB as a safety precaution.