112 lines
5.2 KiB
ReStructuredText
112 lines
5.2 KiB
ReStructuredText
============
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Introduction
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============
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Warewulf is an operating system provisioning platform for Linux clusters. Since
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its initial release in 2001, Warewulf has become the most popular open source
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and vendor-agnostic provisioning system within the global HPC community.
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Warewulf is known for its massive scalability and simple management of stateless
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(disk optional) provisioning.
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Warewulf leverages a simple administrative model centralizing administration
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around virtual OS images which are used to provision cluster nodes. This means
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you can have hundreds or thousands of cluster nodes all booting and running on
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the same OS image. As of Warewulf v4, the OS image can be managed using
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industry-standard container tooling and/or CI/CD pipelines. This can be as
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simple as DockerHub or your own private GitLab CI infrastructure. With this
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architecture, Warewulf combines the best of High Performance Computing (HPC),
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Cloud, Hyperscale, and Enterprise deployment principles to create and maintain
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large scalable stateless clusters.
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Warewulf is used most prominently in High Performance Computing (HPC) clusters,
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but its architecture is flexible enough to be used in most any clustered Linux
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environment, including clustered web servers, rendering farms, and even
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Kubernetes and cloud deployments.
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Warewulf design
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===============
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Warewulf has had a number of iterations since its inception in 2001, but its
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design tenets have always remained the same: a simple, scalable, stateless, and
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flexible provisioning system for all types of clusters.
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* **Lightweight**: Warewulf provisions stateless operating system images and
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then gets out of the way. There are no underlying system dependencies or
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requisite changes to the provisioned cluster node operating system.
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* **Simple**: Warewulf is used by hobbyists, researchers, scientists, engineers
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and systems administrators alike.
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* **Flexible**: Warewulf can address the needs of any environment--from a
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computer lab with graphical workstations, to under-the-desk clusters, to
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supercomputing centers providing HPC services to thousands of users.
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* **Agnostic**: From the Linux distribution of choice to the underlying
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hardware, Warewulf is agnostic and standards compliant. From ARM to x86, Atos
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to Dell, Debian, SUSE, Rocky, CentOS, and RHEL, Warewulf can be used in most
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any environment.
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* **Secure**: Warewulf supports SELinux out-of-the-box. Just install SELinux in
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your OS image and let Warewulf do the rest!
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* **Open Source**: Warewulf is and has always been open source. It can be used
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in any environment, whether public, private, non-profit, or commercial. And
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the Warewulf project is always welcoming of contribution from its community of
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users, with major features often beginning as external contributions.
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Warewulf architecture
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=====================
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Warewulf v4 has a simple but flexible base architecture:
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A **Warewulf server** stores information about the cluster and the nodes in it,
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and provides a command-line interface (``wwctl``) for managing nodes, their
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images, and their overlays.
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**Cluster nodes** are defined in a flexible `YAML
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<https://en.wikipedia.org/wiki/YAML>`_ file, including their network
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configuration and image and overlay assignments.
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**Node profiles** provide a flexible abstraction for applying configuration to
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multiple nodes.
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**Operating system images** provide a bootable image, including the kernel
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that will be used to boot the cluster node. OS images provide the base operating
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system and, by default, run entirely in memory. This means that when you
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reboot the node, the node retains no information about Warewulf or how it
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booted; but it also means that they return to their initial known-good state.
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**Overlays** customize the provisioned operating system image with static files
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and dynamic templates applied with the OS image and, optionally, periodically
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at runtime.
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Beowulf overview
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================
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Warewulf is designed to support the original `Beowulf Cluster
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<https://en.wikipedia.org/wiki/Beowulf_cluster>`_ concept. (Thus its name, a
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soft\ **WARE** implementation of the beo\ **WULF**.) The architecture is
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characterized by a group of similar cluster nodes all connected together using
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standard commodity equipment on an internal cluster network. The server node
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(often historically referred to as the "master" or "head" node) is "dual homed"
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(i.e., it has two network interfaces) with one of these network interfaces
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attached to an external network and the other connected to the internal cluster
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network.
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.. image:: beowulf_architecture.png
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:alt: Beowulf architecture
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This simple topology is the foundation for creating a scalable HPC cluster
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resource. Even today, almost 30 years after the inception of this architecture,
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this is the baseline architecture that virtually all HPC systems are built to.
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An HPC cluster often includes dedicated storage, scheduling and resource
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management, monitoring, interactive systems, and other components. For smaller
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systems, many of these components can be deployed to a single server node; but,
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as the system scales, it may be better to have groups of nodes dedicated to
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these different services.
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Warewulf is flexible enough to start with a simple "head node" Beowulf style
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cluster deployment and to grow as needs for the cluster and its environment
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change.
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