Author: Danilo Chiacchio

Using iPerf3 on an ESXi host is a practical way to measure network throughput between virtualization endpoints and verify whether a specific network path is delivering the performance expected from the infrastructure. In this lab, I will use the iPerf3 utility available on ESXi to test traffic between two ESXi hosts and between an ESXi host and a virtual machine. This can be useful when troubleshooting low throughput on networks used by services such as vSAN, vMotion, management, or other VMkernel-based traffic. The most important part of an iPerf test is making sure that the traffic uses the network path…

Last week, I rebooted a physical Red Hat Enterprise Linux 8 server after applying security updates that included a new kernel. The reboot itself completed normally, but there was one unexpected result: none of the Docker containers came back online. This was a DEV server running Docker Engine with several containers. I expected the applications to return automatically after the host reboot, but every container remained stopped until I started them manually. The problem was not the kernel update or Docker itself. The containers had been created without a restart policy, so Docker had no instruction to start them again…

High-performance computing (HPC) brings together compute resources to solve demanding problems that are too large or time-consuming for a single computer. Many HPC environments use clusters: networked nodes that run parallel workloads, supported by storage systems and a workload manager such as Slurm. Parallel execution can reduce the time needed to solve a problem when the work can be divided effectively; communication and synchronization between tasks also affect performance. This introduction explains how nodes and the compute, network, and storage layers fit into an HPC environment, then introduces Slurm’s role in allocating resources and managing jobs. It is a conceptual…

Linux lets administrators adjust a process’s nice value to influence how the normal CPU scheduler treats it relative to competing tasks. A lower nice value gives a task more scheduling weight; a higher value makes it more willing to yield CPU time. This is a relative preference, not a reserved CPU allocation or a guarantee that one process will always run first. In this RHEL 8 lab, we inspect nice values with top and ps, start a command with nice, and change a running process with renice. The examples also show why permissions matter when increasing a process’s scheduling priority.…

SSH public-key authentication lets a user connect to a remote RHEL 8 server without sending the account password for each login. The client proves access using a private key, while the server checks the matching public key stored for the target account. The private key stays on the client and must never be copied to the server or shared. In this lab, we generate an RSA key pair, install its public key on a remote host with ssh-copy-id, and test the connection. The procedure uses root to match the original example, but for routine administration – especially automation – use…

PowerFlex Manager can authenticate users against an external directory such as Microsoft Active Directory, while its role mappings determine what those users can do after sign-in. This lets administrators manage account membership in Active Directory and assign PowerFlex Manager permissions to directory groups, instead of creating a separate local account for every user. This walkthrough uses PowerFlex Manager 4.5.2 and Active Directory on Windows Server 2022 in a nested lab. It covers adding the directory service, mapping two Active Directory groups to PowerFlex Manager roles, and testing access with a member of each group. The exact directory names and search…