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 Thank to: https://programmerah.com/ Environmental Science: Ubuntu 20.04.3-live-server Hyper-V virtual environment Problem Description: Ubuntu 20.04.3 fails to start sshd with error: failed to start OpenBSD secure shell server sshd – T prompt sshd: no hostkeys available – exiting. Solution: 1. Check whether the SSH service is enabled PS  -  e  |  grep ssh No response 2. Install ssh apt update apt - get install openssh - server openssh - client Prompt installed 3. Implementation /etc/ init . d / ssh start fail to start Continue to execute  ssh - keygen  - A Restart successfully

 Thank to: https://www.tecmint.com/cache-content-with-nginx/ NGINX   being a consolidated open-source, high-performance web server that speeds up content and application delivery, enhances security, and improve scalability. One of the most common use cases of   Nginx   is a   Content Caching , which is the most effective way to boost the performance of a website. Read Also :  10 Top Open Source Caching Tools for Linux You can use  NGINX  to accelerate local origin servers by configuring it to cache responses from upstream servers and also to create edge servers for content delivery networks ( CDNs ). NGINX powers some of the largest CDNs. When configured as a cache, NGINX will: cache static and dynamic content. improve dynamic content performance with micro-caching. serve stale content while revalidating in the background for better performance. override or set Cache-Control headers, and more. In this article, you will learn how to configure  NGINX  as a  Content Caching  in Linux to m

 Thank to: https://argonsys.com/ Use of DCPROMO is still the proper way to remove a DC server in an Active Directory infrastructure. The following video provides an example of these steps: Certain situations, such as server crash or failure of the DCPROMO option, require manual removal of the DC from the system by cleaning up the servers metadata. The following detailed steps will help you accomplish this: Removing metadata via Active Directory Users and Computers Log in to DC server as Domain/Enterprise administrator and navigate to  Server Manager > Tools > Active Directory Users and Computers Expand the  Domain > Domain Controllers Right click on the Domain Controller you need to manually remove and click  D elete Click  Yes  to confirm within the Active Directory Domain Services dialog box In next dialog box, select  This Domain Controller is permanently offline and can no longer be demoted using the Active Directory Domain Services Installation Wizard (DCPROMO)  and click