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.…

Patching an ESXi host from the command line is useful when you need a controlled maintenance procedure for a standalone host or a host managed outside a cluster lifecycle workflow. The recommended profile-based method uses an offline bundle ZIP and esxcli software profile update. It is not the same as installing an ESXi ISO. Before changing a production host, confirm…

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 or account/partition combination specified error usually means that the user submitting the job does not have a valid Slurm accounting association for the requested cluster, account, and, when applicable, partition. I encountered this problem while testing job submission in my Slurm lab. The Linux user existed normally on the login and compute nodes, and the shared…

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…