Author: Danilo Chiacchio

Ansible becomes much easier to understand when you stop looking at individual concepts and start using it to solve a real administrative task. In this guide, I will use a lab environment to create and run a first Ansible playbook against multiple Linux servers. Instead of building a simple “Hello World” example, the playbook will perform an actual system administration task: ensure that the NFS client package is installed and that the required NFS client target is running on a group of HPC nodes. The goal is not only to show the YAML syntax. We will build the inventory, validate…

High disk partition usage Linux systems can quickly become a critical issue, whether you are managing a production server, a virtual machine, or an HPC login node. When I investigate storage problems, I start by identifying which filesystem is full before narrowing the search to the directories and files responsible for the excessive disk usage. Over the years, I have found that Linux provides all the built-in tools needed to diagnose disk space problems without installing additional software. By combining commands such as df, du, find, and lsof, it is possible to identify storage bottlenecks efficiently and reduce the time…

Slurm jobs stuck in COMPLETING state can indicate that one or more compute nodes have not finished cleaning up the resources associated with a workload. In a healthy Slurm-managed HPC cluster, a job normally moves from RUNNING to COMPLETING and then quickly reaches a final state such as COMPLETED, FAILED, or CANCELLED. The COMPLETING phase is expected, but it should usually be brief. When a job remains there for several minutes or longer, Slurm may still be waiting for processes to terminate, an epilog script to finish, a filesystem operation to return, or communication with a compute node to recover.…

A file-based backup can be one of the most valuable recovery options when a vCenter Server Appliance becomes unavailable or must be rebuilt. In this lab, I restore a vCenter Server Appliance from an existing file-based backup using the graphical VCSA installer. The restore workflow deploys a new appliance first and then imports the configuration and data stored in the backup. This article is based on a lab environment originally tested with vCenter Server 7.0.3.01600. The general two-stage restore workflow is still used in newer vCenter releases, but screens, prerequisites, supported protocols, and recovery considerations may change between versions. Before…

TCP retransmissions on Linux are a normal part of TCP communication, but an excessive number of retransmitted packets often indicates a problem somewhere between the application and the remote endpoint. Packet loss, congestion, overloaded systems, faulty interfaces, bad cabling, MTU mismatches, and unstable network paths can all produce similar symptoms. When investigating TCP retransmissions on Linux, the challenge is rarely detecting that retransmissions exist. The real task is determining where they originate, whether they are occasional or persistent, and whether they are affecting application performance. Looking at only one command usually provides an incomplete picture. A useful investigation combines kernel…

The Stats Primary Election alert in vSAN Skyline Health indicates that the vSAN Performance Service cannot identify or elect the Stats Primary node required to collect and manage performance statistics. I encountered this condition in a vSAN ESA lab cluster where the CMMDS Primary was correctly elected, but no Stats Primary could be detected. In this guide, I will show the investigation I performed, the standard recovery steps that should be attempted first, and the final cleanup that resolved the issue in my lab. The important point is that manually deleting the .vsan.stats object should not be the first troubleshooting…