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Change Runlevel of Rocky Linux 8 without rebooting

You may use the command “telinit” to change the SysV system runlevel without the need to reboot. You will need root access to run the command

Use 1: Single User Mode

# telinit S

Use 2: To go to Graphical.Target

# telinit 5

Use 3: To go to Multi-User.Target

# telinit 3

Use 4: To Reload daemon configuration. This is equivalent to systemctl daemon-reload.

# telinit q

To verify, you can use the command systemctl get-default

# systemctl get-default
graphical.target
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Optimizing Firewalld Configuration with Ansible’s with_items Parameter

Ansible is great for configuring host-based firewall like Firewalld. One thing you will note is that we are using with_items parameter a lot and it is very useful in this case since we have a number of parameters within items. 

- name: FirewallD Rules (Ports)
  firewalld:
    permanent: yes
    immediate: yes
    port: "{{item.port}}/{{item.proto}}"
    state: "{{item.state}}"
    zone: "{{item.zone}}"
  with_items:
    - {port: "80", proto: "tcp", state: "enabled", zone: "public" }
    - {port: "80", proto: "udp", state: "enabled", zone: "public" }
    - {port: "443", proto: "tcp", state: "disabled", zone: "public" }
    - {port: "443", proto: "udp", state: "disabled", zone: "public" }


- name: FirewallD Rules (Services)
  firewalld:
    permanent: yes
    immediate: yes
    service: "{{item.service}}"
    state: "{{item.state}}"
    zone: "{{item.zone}}"
  with_items:
    - {service: "cockpit", state: "disabled", zone: "public" }

- name: Turn on Firewalld.service on Compute Nodes
  systemd:
    name: firewalld
    state: started
    enabled: yes
  when:
    - ansible_os_family == "RedHat"
    - ansible_distribution_major_version == "8"

References:

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Updating ANSYS 2023R2 License Server Information for Linux Client using the command line

If you are updating ANSYS License Server Information for ANSYS Client using only the command line, do the following

# vim usr/local/ansys_inc/shared_files/licensing/ansyslmd.ini
SERVER=1055@IP_Address_Of_ANSYS_LIC_SVR
ANSYSLI_SERVERS=2325@IP_Address_Of_ANSYS_LIC_SVR

Make sure the 1055, 1056, 2325 Ports of the License Server are opened.

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Enterprise Container Management Solutions – SuSE Rancher

What is SuSE Rancher?

Website: https://www.rancher.com/ (by SuSE)

Rancher Labs builds innovative, open source container management solutions for enterprises leveraging containers to accelerate software development and improve IT operations. The flagship product, Rancher, is a complete container management platform that makes it easy to manage all aspects of running containers in development and production environments, on any infrastructure. RancherOS is a minimalist Linux distribution which is perfect for running Docker containers at scale.

View on-demand recordings of past Rancher demos, online meetups, and Kubernetes tutorials at Rancher Youtube Channel. ( Rancher Labs )

This guide walks you through the process of adopting an enterprise container management platform (Dummies e-copy).

This guide will help security teams understand the attack surface for Kubernetes deployments and how attackers can exploit vulnerabilities. Get the e-copy of the Ultimate Guide to Kubernetes Security

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Could not load the Qt platform plugin “xcb” in “” even though it was found in Rocky Linux 8

I was installing ANSYS 2023 R2 on Rocky Linux 8 and I encoutnered the error

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: xcb.

Solution

# dnf install python3-qt5
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Mounting NTFS on Rocky Linux 8

If you are planning to mount like a portable drive using Windows NTFS File System on the Rocky Linux 8, what you will see immediately when you issue the command after you plug the portable drive in

# mount /dev/sdd1 /data1
mount: /data1: unknown filesystem type 'ntfs'.

Step 1: Enable EPEL Repo

# dnf install epel-release

Step 2: Install NTFS-3g

# dnf install ntfs-3g

In some blogs written elsewhere, these 2 packages are more than enough, but I was still having issues. In my situation, I need to put in 5 packages

Step 3: Install all NTFS-3g packages

# dnf install *ntfs*

This time it works for me.

Step 4: Simply mount (Hooray!)

 # mount /dev/sdd1 /data1
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Enabling Nvidia Tesla 4 x A100 with NVLink for MPI

I was having issues with the Applications like NetKET to detect and enable MPI.

Diagnosis

  1. I have installed OpenMPI and enabled CUDA during the configuration.
  2. CUDA Libraries including nvidia-smi has been installed without issue. But running, nvidia-smi topo –matrix, I am not able to see NVLink similar to

In fact, when I run NetKet on CUDA with MPI, the error that was generated was 

mpirun noticed that process rank 0 with PID 0 on node gpu1 exited on signal 11 (Segmentation fault)."

Solution

This forum entry provided some enlightenment. https://forums.developer.nvidia.com/t/cuda-initialization-error-on-8x-a100-gpu-hgx-server/250936

The solution was to disable the Multi-instance GPU Mode which is enabled by default. Reboot the Server and it should see

nvidia-smi -mig 0

Enabling Persistence Mode

Make sure the configuration stays after a reboot. 

# systemctl enable nvidia-persistenced.service
# systemctl start nvidia-persistenced.service
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Basic use of nvidia-smi commands

There is a very good article written by Microway on this utility. Take a look at nvidia-smi: Control Your GPUs

What is nvidia-smi?

nvidia-smi is a command line utility, based on top of the NVIDIA Management Library (NVML), intended to aid in the management and monitoring of NVIDIA GPU devices.

Installation

Do take a look at NVIDIA CUDA Installation Guide for Linux for more information

Query GPU Status

$ nvidia-smi -L

Query overall GPU usage with 1-second update intervals

$ nvidia-smi dmon

Query System/GPU Topology and NVLink

$ nvidia-smi topo --matrix
$ nvidia-smi nvlink --status

Query Details of GPU Cards

$ nvidia-smi -i 0 -q
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Basic Use of Nvidia Data Centre GPU Manager (DCGM)

For more information, take a look at The NVIDIA® Data Center GPU Manager (DCGM) . According to the Information,

The NVIDIA® Data Center GPU Manager (DCGM) simplifies administration of NVIDIA Datacenter (previously “Tesla”) GPUs in cluster and datacenter environments. At its heart, DCGM is an intelligent, lightweight user space library/agent that performs a variety of functions on each host system:

  • GPU behavior monitoring
  • GPU configuration management
  • GPU policy oversight
  • GPU health and diagnostics
  • GPU accounting and process statistics
  • NVSwitch configuration and monitoring

This functionality is accessible programmatically though public APIs and interactively through CLI tools. It is designed to be run either as a standalone entity or as an embedded library within management tools. This document is intended as an overview of DCGM’s main goals and features and is intended for system administrators, ISV developers, and individual users managing groups of NVIDIA GPUs.

Installation

Assuming you are using RHEL Derivative like Rocky Linux 8, installation is a breeze

# dnf config-manager --add-repo http://developer.download.nvidia.com/compute/cuda/repos/$distribution/x86_64/cuda-rhel8.repo
# dnf install -y datacenter-gpu-manager

Enable the DCGM systemd service (on reboot) and start it now

# systemctl --now enable nvidia-dcgm
# systemctl start nvidia-dcgm

Basic Usage – Discovery

#  dcgmi discovery -l

Basic Usage – Diagnostic

To run a diagnostic test, you can use the command. You can decide on the level of diagostic. For example, 

# dcgmi diag -r 2

If you want a more comprehensive diagnostic, you can use the command, you can use -r 3

# dcgmi diag -r 3

Basic Usage – NVLink Status

# dcgmi nvlink -s
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Allowing users to bypass PBS-Professional Scheduler to SSH directly into the Compute Node

For some special users like Adminsitrators, who needs to SSH directly into the compute instead of submitting to the scheduler with using root, you may want to do the following:

At the Compute Node

# vim /var/spool/pbs/mom_priv/config

Find the $restrict_user_exceptions

$clienthost 192.168.x.x
$clienthost 192.168.y.y
$restrict_user_maxsysid 999
$restrict_user True
$restrict_user_exceptions user1
$usecp *:/home/ /home/

Restart the PBS Service

# /etc/init.d/pbs restart