Useful links

Here is a list of useful links that I think it can be useful when having specific trouble.

Linux tutorials site:

  3. – ex. How to block or sinkhole domains in BIND


  1. RHEL 7 Security Guide – Chapter 5. Using Firewalls
  2. Dynamic firewall with firewalld
  3. Introduction to Firewalld Basics
  4. How to Mount a NTFS Drive on CentOS / RHEL / Scientific Linux
  5. Setting Up “NTP (Network Time Protocol) Server” in RHEL/CentOS 7
  6. Setting Up Logrotate on RedHat Linux
  7. VMware: Timekeeping best practices for Linux guests
  8. Adding a New Disk Drive to an RHEL 6 System
  9. How to Create Partition on Linux for >2TB Size using Parted GPT
  10. How to Install and Configure Bind Chroot DNS Server on CentOS 6.3 x86_64
  11. Extend the size of ext3 partition online in a virtual machine
  12. How to Increase the size of a Linux LVM by expanding the virtual machine disk
  13. Install Oracle Java JDK/JRE 7u25 on Fedora 19/18, CentOS/RHEL 6.4/5.9
  14. Install NVIDIA Drivers in RHEL/CentOS/Fedora and Debian/Ubuntu/Linux Mint
  15. Linux Directory Structure and Important Files Paths Explained
  16. Shell Scripting
  17. How to Create a Centralized Log Server with Rsyslog in CentOS/RHEL 7
  18. How To Centralize Logs with Rsyslog, Logstash, and Elasticsearch on Ubuntu 14.04
  19. Red Hat Enterprise Linux Documentation
  20. Red Hat / CentOS IPv6 Network Configuration
  21. 29 Practical Examples of Nmap Commands for Linux System/Network Administrators
  22. Red Hat Enterprise Linux 7 Security Guide: 4.5. Using Firewalls
  23. Introduction to FirewallD on CentOS
  24. Introduction to Firewalld Basics
  25. CentOS Repositories
  26. Mega backup: copies in the cloud in GNU / Linux
  27. How To Create a systemd Service in Linux (CentOS 7)
  28. Useful SystemD commands (hints for systemctl or systemctl vs chkconfig and service)
  29. CentOS 7 – The perfect desktop guide
  30. CentOS 7 – The perfect desktop, second guide!
  31. How to configure multiple instances of sshd in RHEL 7
  32. Setting Up grub2 on CentOS 7
  33. How To Set Up Multi-Factor Authentication for SSH on CentOS 7
  34. adcli – Easy Way To Join RHEL/CentOS System To Active Directory Domain
  35. Efficient Ways To Read The Log Files In Linux
  36. Reset a lost root password in under 5 minutes
  37. How to install Icinga 2 and Icinga 2 web on CentOS 7?
  38. Using Hurricane Electric free DNS service for slaves, revisited
  39. A sysadmin’s guide to SELinux: 42 answers to the big questions
  40. How to Install, Configure and Use Firewalld in CentOS and Ubuntu
  41. Install Nvidia Drivers on CentOS
  42. VirtualBox Guest Additions on Fedora 29/28, CentOS/RHEL 7.5/6.10/5.11
  43. Install ImageMagick (Image Manipulation) Tool on RHEL/CentOS and Fedora
  44. How to Install Python 3 on CentOS 7
  45. Replacing a failing RAID 6 drive with mdadm
  46. More stupid Bash tricks: Variables, find, file descriptors, and remote operations
  47. I/O reporting from the Linux command line
  48. Getting started with ApacheDS – LDAP Server and Directory Studio
  49. How to Setup and Manage Log Rotation Using Logrotate in Linux
  50. RHEL: Setup an IPERF3 Server

Linux – Systemd:

  1. Using systemd Path Units to Monitor Files and Directories

CentOS 8:

  1. How to Disable SELinux on CentOS 8
  2. How to Add Swap Space on CentOS 8
  3. How To Add Swap Space on CentOS 8
  4. Secure Apache with Let’s Encrypt on CentOS 8
  5. How to Install PHP on CentOS 8
  6. How To Enable and Install EPEL Repo on CentOS 8.x
  7. How To Enable EPEL Repository On CentOS 8 / RHEL 8
  8. How To Set or Change Timezone on CentOS 8
  9. How To Install ImageMagick and PHP Imagick on CentOS 8 / RHEL 8
  10. How to restart CentOS or RHEL server safely

Let’s Encrypt:

  1. Using Let’s Encrypt DNS-01 challenge validation with local BIND instance
  2. Host multiple websites with HTTPS on a single server


  1. Run MySQL Querys with Powershell

DNS Tools:

  1. DNS Check
  2. DNS Inspect
  3. ZoneCheck
  4. DNSstuff
  5. intoDNS
  6. How to Find DNS (Domain Name Server) Records On Linux Using the Dig Command
  8. DNSViz – A DNS visualization tool

Secure Website Development:

  1. Security Headers


  1. SQL Indexing and Tuning e-Book
  2. How to build an active-active-active cluster with RHEL 8 and Percona MySQL


  1. IPv4/IPv6 subnet calculator
  2. How to install phpIPAM on CentOS 7


  1. Online regex tester and debugger: JavaScript, Python, PHP, and PCRE


  1. Using Office 365 as a Smart Host with Postfix
  2. How to rewrite outgoing address in Postfix

Microsoft Office:

  1. Tools to manage Office 2013 volume activation

Windows 10:

  1. How to Uninstall Programs on Windows 10


  1. SAML Developer Tools


  1. [How to] Whitelist Cloudflare IP’s in Wordfence
  2. Protect Your Sites from the EU Cookie Law
  3. How to Speed Up WordPress and Boost Performance on an Ubuntu 20.04 VPS


  1. The most important Firefox command line options


  1. How to install Tomcat 9 on CentOS 7


  1. How To Create an SSL Certificate on Apache for CentOS 7
  2. Generating a Self Signed SSL Certificate in RHEL/CentOS 7
  3. Qualys SSL Server Test
  4. Show the certificate chain of a local X509 file

Fiber Optics:

  1. Picking the right fiber connector – PC, UPC or APC


  1. How to Back Up and Copy PuTTY Sessions and Settings to Another PC
  2. Guide: PuTTY and SSH Key-Based Authentication (Windows)
  3. Saving your PuTTY username and password in a Windows Shortcut


  1. Redirect HTTP to HTTPS in Apache
  2. Secure Apache with Let’s Encrypt on CentOS 8