Reference

xOPS Repository Structure

xOPS follows Ansible best practices with a clear separation of concerns:

Directory	Purpose
roles/	150+ reusable Ansible roles (the building blocks of configuration: one role per service or subsystem).
group_vars/	Variables scoped per system or host group (e.g., group_vars/juwels/), allowing per-cluster customization.
host_vars/	Variables specific to individual nodes, for host-level tuning.
files/	Static configuration files deployed as-is: SSH keys, certificates, pre-built configs.
templates/	Jinja2 templates rendered at deploy time (e.g., SLURM configs, kickstart files).
vault/	Encrypted secrets (passwords, API tokens) managed with Ansible Vault and GPG.
juwels/, jureca/, ...	Per-system inventory directories defining which hosts belong to which groups.
*.yml (root)	Top-level playbooks — one per system — that orchestrate which roles run on which hosts.

How Changes Are Applied

Technology Stack

• Configuration Management: Ansible (agentless, SSH-based automation)

• Operating Systems: Red Hat Enterprise Linux, Rocky Linux

• Job Scheduling: SLURM, UNICORE

• Parallel Filesystems: IBM Spectrum Scale (GPFS), Ceph, NFS

• Interconnect: InfiniBand (Mellanox/NVIDIA OFED), Ethernet

• Accelerators: NVIDIA & AMD GPUs (driver & runtime management)

• Monitoring: Prometheus, Grafana, Loki, Alertmanager

• Containers: Apptainer (Singularity), Podman, Kubernetes

• High Availability: Pacemaker/Corosync, HAProxy, Keepalived

• Secrets Management: Ansible Vault with GPG encryption

• Source Control & CI/CD: GitLab, GitLab-CI, Ansible AWX

Glossary

Term	Definition
Ansible	An open-source IT automation engine that manages configuration, deployment, and orchestration over SSH — no agent software is required on managed nodes.
Playbook	A YAML file that declares what should be configured on which hosts. Think of it as a recipe that Ansible follows step by step.
Role	A self-contained, reusable unit of automation (e.g., “install and configure SLURM”). Roles are the building blocks assembled by playbooks.
Inventory	A listing of all servers (nodes) organised into groups. Each HPC system has its own inventory.
Configuration as Code	The practice of managing IT infrastructure configuration through machine-readable definition files rather than manual configuration, enabling version control, review, and repeatable deployments.
HPC	High-Performance Computing — using supercomputers and parallel processing to solve large-scale computational problems in science, engineering, and AI.
SLURM	Simple Linux Utility for Resource Management — the industry-standard job scheduler that allocates compute resources to user workloads on HPC clusters.
GPFS	General Parallel File System (IBM Spectrum Scale) — a high-performance clustered filesystem designed for large-scale data-intensive workloads.