Recently, I have faced the below issue with a new Sendmail installation on a Linux system. While sending emails to a specific domain like [email protected] are showing the error “stat=User unknown”. The issue was happening for a specific domain only. Sending emails to other domain were working properly. The log file entries are looks like below: Jan 7 08:36:04 tecadmin sendmail[22497]: 1078a4RD022497: from=www-data, size=679, class=0, nrcpts=1, msgid=, relay=www-data@localhost Jan 7 08:36:04 tecadmin sendmail[22497]: 1078a4RD022497: [email protected], ctladdr=www-data (33/33), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30679, relay=[127.0.0.1] [127.0.0.1], dsn=5.1.1, stat=User unknown Jan 7 08:36:04 tecadmin sendmail[22497]: 1078a4RD022497: 1078a4RE022497: DSN: User unknown Solution: After troubleshooting the…
Author: Rahul
I, Rahul Kumar am the founder and chief editor of TecAdmin.net. I am a Red Hat Certified Engineer (RHCE) and working as an IT professional since 2009..
Gitlab is a web-based DevOps lifecycle management tool developed by GitLab Inc. Similar to the Github, Gitlab is also another popular Git version control system used by large number of users. Gitlab also provides great features like issue tracking, To-Do list, continuous integration and deployment (CI/CD) pipelines for the applications. Gitlab also supports integration with various services. The Community edition of Gitlab is available free for use on development and production environment. It provides large number of features required for small to large scale companies. The enterprise edition provides more features but required a paid license. This tutorial will describe…
We always say, Security first. It should be the first priority to keep your hard work safe from the hackers. This tutorial will take few minutes to secure Gitlab server using Let’s Encrypt SSL certificates. Let’s Encrypt provides free SSL certificates to secure your domains and an easy way to auto updates. This tutorial will help you to secure Gitlab service with Let’s Encrypt SSL certificate with enabling the auto renew feature. If you are going with a fresh installation have a look at below guides. Install and Configure Gitlab on Ubuntu 20.04 Install and Configure Gitlab on CentOS 8…
Gitlab is a web-based DevOps lifecycle management tool developed by GitLab Inc. It provides git version control repository management, issue tracking, a To-Do list, continuous integration, and deployment (CI/CD) pipelines for the applications. Gitlab also supports integration with various services. The Community edition of Gitlab is available free for use in the development and production environment. It provides a large number of features required for small to large-scale companies. The enterprise edition provides more features but required a paid license. This tutorial will help you to install Gitlab on Ubuntu 20.04 LTS Linux system. You are going to install Gitlab…
Netdata is an open source tool designed for the real-time system performance monitoring solution. It collects real-time metrics for system activities like CPU uses, memory uses, bandwidth uses and disk activities etc. And displays the information on web interface with graphical charts. Netdata official team recommend to install netdata monitoring tool using the kickstart script. But this tutorial will help you to install Netdata on Ubuntu using default repositories. This tutorial describe you to how to install Netdata on Ubuntu 20.04 LTS Linux system. Prerequisites Login to your Ubuntu 20.04 LTS Linux system with sudo privileged account. Install Netdata on…
In the vast universe of Linux commands, dig stands out as an essential tool for network administrators, cybersecurity professionals, and IT enthusiasts. The Domain Information Groper, or dig, is a powerful command-line utility used for querying DNS (Domain Name System) servers. It helps in troubleshooting DNS issues and fetching information about domain names, including IP addresses, mail servers, and DNS records. This comprehensive guide aims to equip you with a deep understanding of the dig command, enriched with real-world examples to help you master its usage. Understanding the Basics of dig Before diving into complex queries, let’s start with the…
Opera is a Chromium-based multi-platform web browser developed by Opera Software. It have multiple features similar to the Google chrome as both are developed on Chromium. You will get a new looks and multiple different features that other browsers, which makes it more powerful. The Opera browser is available under the Snapcraft packages. Also the Opera team provides an PPA for installing Opera on Ubuntu systems. This tutorial help you to install Opera web browser on Ubuntu 20.04 LTS Linux system. Prerequisites A running Ubuntu 20.04 system with Desktop Shell access with sudo privileged account Installing Opera on Ubuntu 20.04…
VNC stands for “Virtual Network Computing” is the set of protocols for sharing desktop systems remotely. There are many software available to access Linux based desktop remotely including, TigerVNC, TightVNC, Vino, vnc4server and many more. TigerVNC is a free, open-source and high-performance VNC server used to control or access Linux based desktop systems remotely. It is a client/server application that allows you to interact with graphical applications on remote machines. This tutorial described you to how to install and configure VNC server on Ubuntu 18.04 Linux system.. Prerequisites By default, Ubuntu Server does not include a Desktop Environment. TigerVNC server…
The su command is also known as switch user. This command is used to become another user during a login session. When invoked without a username, su defaults switch to the super user. Basically, the su command is used to change current logged in user to another user without logged out from system. It is an frequently used command mostly by the Linux terminal users. This tutorial will help you understand the uses of Linux su command with examples. Syntax: su [OPTIONS] [USER] [OPTIONAL ARGS…] su Command Examples in Linux Let’s begin with a basic example. I’m Logged in to…
Linux is the best and most-used open source operating system. The Linux users have a large number of options to choose operating system. You have options to choose desktop for your Linux systems. But still Linux professionals love the command line to work. Mainly the Linux server editions comes with command line option only, which create them lighter and faster. The Linux users uses shell to interact with operating systems. In which the Bash (Born Shell) is the most used shell and available default on most systems. Now a days Zsh (Z Shell) is also getting popularity between the users…