System Administration


  1. Basic Overview of Ansible

Configuration and Hardware

  1. Using dmidecode to find hardware information
  2. Massive DNS Requests caused by IPv6
  3. Tools to Show your System Configuration

Disk and Partition

  1. Checking Disk Usage Examples
  2. Unable to open /dev/sdb with fdisk

Environment Modules

  1. Installing and Configuring Environment Modules on CentOS 5
  2. Usage of Environment Modules on CentOS and in Cluster
  3. Installing and Configuring Environment Modules on CentOS 6

File Handlers

  1. Cannot set user id: Resource temporarily unavailable while trying to login or su as a local user in CentOS
  2. Mount an ISO File in Linux
  3. Making ISO using mkisofs

General Linux Tools

  1. Using the command “ls” options and arguments
  2. MobaXTerm a Swiss-Army Knife for Remote Computing
  3. Unpacking file with tbz extension


  1.  Speeding up kernel crash hang analysis with the kernel log

Kick Start

  1. Basic Kickstart on CentOS 6 (Part 1)
  2. Basic Kickstart on CentOS 6 (Part 2)


  1. Tweaking the Linux Kernel to manage memory and swap usage
  2. Clearing memory cache
  3. Finding the maximum memory used by your Application

Nagios and Plugins

  1. Installing Check Disk IO Plugins via NRPE on CentOS 5
  2. Incorporating PNP 0.4.x (PNP is not Perfparse) with Nagios 3 and CentOS 5
  3. Installing and checking /proc/mount using Nagios Plugins on CentOS 5
  4. Installing check_mk for Nagios on CentOS 5

NFS Performance and Issues

  1. Using nfsstat to troubleshoot NFS performance issues
  2. showmount fails with clnt_create: RPC: Program not registered from a NFS client communicating with a NetApp filer
  3. mount.nfs: requested NFS version or transport protocol is not supported


  1. Configuring OpenLDAP on CentOS 6 (Part 1)

Performance Monitoring

  1. Using mpstat to display SMP CPU statistics
  2. Basic Overview and use of NMON on CentOS 5
  3. Using strace as a troubleshooting tool
  4. Compiling Valgrind on CentOS 5
  5. Brief overview of Valgrind usage
  6. Using iostat to report system input and output
  7. Using qperf to measure network bandwidth and latency
  8. Understanding Load Average in Linux

Performance Tuning

  1. Using Tuned to tune CentOS 6 System
  2. How is the nproc hard limit calculated and how do we change the value on CentOS 7


  1. Setting up 2 Gateways with a Default Gateway for most Traffic and the 2nd Gateway for selected Subnet Traffic on Rocky Linux 8


  1. Fixing out of memory Issues in Rsync


  1. Permission denied when Starting Screen


  1. Disable SElinux in CentOS 7


  1. Configuring CentOS 5 as an SMTP Mail Client with sendmail


  1. Recommended /etc/sshd_config parameters for OpenSSH
  2. Speeding up SSH connections
  3. Automate pushing of ssh-copy-id to multiple servers
  4. Helping users to SSH without password into the Compute Nodes manually
  5. SSH Login without Password
  6. Reinstating user password-less access to compute nodes
  7. Building Public Key, SSH Private Key and Authorized Key
  8. Unable to open a connection to your SSH authentication agent
  9. SSH and X-Forwarding on CentOS 6
  10. Allow SSH Root Login From Selected IP Addresses
  11. How to prevent SSH from disconnecting
  12. Encountering SSH “Permission denied, please try again.”


  1. Using TurboVNC 0.6 and VirtualGL 2.1.4 to run OpenGL Application Remotely on CentOS


  1. xRDP Connection Errors on CentOS 6
  2. Fixing Authentication is required to set the network proxy used for download packages on CentOS 6
  3. xrdp_mm_process_login_response: login failed on CentOS 6


  1. Using xsos to summarise System Information


  1. timeout in locking authority file /home/user1/.Xauthority


  1. YumRepo Error: All mirror URLs are not using ftp, http[s] or file
  2. Install and Enable EPEL Repository for CentOS 7.x