Linux ss lsof fuser commands are essential tools for investigating network connections, open files, busy ports, and processes using system resources. When a Linux server refuses connections, reports that a port is already in use, or prevents a filesystem from being unmounted, these commands can quickly reveal what is happening. Although their functions sometimes overlap, each command approaches troubleshooting differently.…

The vim-cmd utility is one of the most useful command-line tools available on a VMware ESXi host. It allows administrators to inspect and manage virtual machines directly from the ESXi Shell or through an SSH session, which can be especially useful when troubleshooting a host or when the vSphere Client is unavailable. In this practical guide, I will show several…

The Slurm invalid account error can occur when a user tries to submit jobs without a valid association in the Slurm database. In this guide, I will demonstrate a real troubleshooting scenario where a job submission fails with an account or account/partition combination error. While testing a Slurm cluster, I received this error when submitting a job using the srun…

A Slurm job pending in the queue does not necessarily mean something is wrong with the cluster or with your batch script. Pending simply means that Slurm accepted the job, but the scheduler has not yet found the conditions required to start it. The important question is why the job is waiting. Fortunately, Slurm normally provides that answer directly through its job…

A vCenter Server backup only becomes valuable when it is created regularly, stored outside the appliance, and can actually be used during a recovery. In this guide, I will configure a file-based backup of vCenter Server using the vCenter Server Management Interface (VAMI). In my lab, a TrueNAS server provides an NFS repository where the scheduled backups are stored. We…