in this tutorial, How to change ssh port another with selinux. The default ssh port 22, when you change port another with rules selinux (SELINUX=enforcing) get error can't change ssh port. Solve problem!( Running command following with root account) File selinux with content SELINUX=enforcing as below: [huupv@huupv ~]$ sudo cat /etc/sysconfig/selinux [sudo] password for huupv: # This file controls the state of SELinux on the system. # SELINUX= can take one of these three values: #     enforcing - SELinux security policy is enforced. #     permissive - SELinux prints warnings instead of enforcing. #     disabled - No SELinux policy is loaded. SELINUX=enforcing # SELINUXTYPE= can take one of these three values: #     targeted - Targeted processes are protected, #     minimum - Modification of targeted policy. Only selected processes are protected. #     mls...

Centos 7 managing services with Systemd. -List all the current loaded targets as command below: $ sudo systemctl list-units -t target Each services has 3 states; enabled, disabled and static. - To list enabled services as command below: $ sudo systemctl list-unit-files --type=service | grep enabled - To start/stop/restart services as command below: # systemctl status <servicename> # systemctl stop <servicename> # systemctl start <servicename> # systemctl restart <servicename> - To check running ntp services as comman below: $ sudo systemctl list-units --type service --all | grep ntp - Set the service to start a boot: # systemctl enable <servicename> - Disable service start-up boot # systemctl disable service The update later related command line "Centos 7 managing services with Systemd" in this article.

Introduction Learn how to use a bash script to change folder permissions recursively with practical examples. This guide includes step-by-step instructions and script samples to effectively manage file permissions in Linux. Managing file permissions is a fundamental task for any system administrator. Often, you need to change the permissions of a directory and all its contents. This guide will demonstrate how to use a bash script to change folder permissions recursively, with examples covering both basic and advanced scenarios. What is Recursive Permission Change? Recursive permission change applies the specified permissions to the target directory and all its subdirectories and files. This approach is particularly useful for ensuring consistent access controls across complex directory structures. Why Use Bash Scripts for Permission Changes? Bash scripts allow for automation, saving time and reducing errors when changing permissions across multiple files and directories. Scripts can b...

tar command is archiving utility. Something, you can retrieve extension .tar.gz or .tar.bz2 file. How to list the contents this without extracting from command line. The syntax tar command as below: tar OPTION File_Name With OPTION : t, --list : List the contents of an archive v : Verbosely list files processed j : Filter archive through bzip2 f : filename  You may reading link as below: Iptables how to How to reset password on centos 7 Bash script example List the contents of .tar.gz file To use tar command for .tar.gz as following: $ tar -tvf links-2.12.tar.gz  The output of links-2.12.tar.gz file as below: -rwxr--r-- 1000/1000      1215 2001-10-05 14:03 links-2.12/mailcap.pl -rwxr-xr-- 1000/1000      4654 2015-06-28 22:13 links-2.12/rebuild -rw-r--r-- 1000/1000       461 2003-05-06 01:10 links-2.12/links_16x16_1.xpm -rw-r--r-- 1000/1000      2410 2003-05-...

Introduction Zimbra is a widely-used email platform, offering robust features for managing emails within organizations of all sizes. Understanding who the top email senders are within your Zimbra system can be crucial for various reasons, such as monitoring email traffic, identifying potential spam sources, and optimizing your email server's performance. In this guide, we will walk you through the process of listing the top sender email addresses in Zimbra using command-line tools. By the end of this article, you'll have a clear understanding of the commands needed to identify the top senders and how to interpret the results to improve your email management practices. Step-by-Step Guide to Listing Top Sender Email Addresses Step 1: Access the Zimbra MTA Server To begin, you need to access the Zimbra Mail Transfer Agent (MTA) server, where Zimbra's log files are stored. These log files contain detailed records of all email transactions processed by your Zimbra system. How t...

Introduction Zimbra Collaboration Suite is a powerful email and collaboration platform used by organizations worldwide. Managing users efficiently is one of its core strengths, and distribution lists play a vital role in streamlining email communication. A distribution list enables administrators to group multiple users under one email address, ensuring seamless communication. This guide will explore how to add an account to a distribution list in Zimbra, highlighting basic and advanced methods. Why Use Distribution Lists in Zimbra? Distribution lists enhance productivity by: Allowing you to send emails to multiple users with a single address. Reducing the time spent managing group communications. Simplifying the process of managing user access to shared mailboxes. Prerequisites Before diving into the steps, ensure you have: Administrative access to the Zimbra server. Basic knowledge of Zimbra’s Command Line Interface (CLI) and Admin Console. The target email account(s) to be added....

Introduction Managing email distribution lists efficiently is crucial for businesses and organizations of all sizes. Zimbra, a robust collaboration suite, offers a powerful command to automate the creation of distribution lists, saving time and reducing manual effort. In this guide, we’ll explore how to use the Zimbra auto-create distribution lists feature, providing step-by-step instructions, practical examples, and answers to frequently asked questions. What Are Zimbra Distribution Lists? Distribution lists are email groups that allow you to send messages to multiple recipients simultaneously. Zimbra simplifies the management of these lists with automation tools that can: Reduce administrative overhead. Ensure consistent list configurations. Improve communication within organizations. How to Auto Create Distribution Lists in Zimbra Prerequisites Before starting, ensure you have: Admin access to your Zimbra server. Zimbra Collaboration Suite (ZCS) installed and configured. Basic knowl...

Introduction If you're encountering the error " Zimbra 451 4.3.5 Server configuration problem" in your zimbra.log , this guide will walk you through the steps to diagnose and resolve the issue effectively. zimbra 451 4.3.5 Server configuration problem The error message typically appears in the zimbra.log file as follows: Jan 22 11:31:36 mta postfix/smtpd[9984]: NOQUEUE: reject: RCPT from unknown[198.54.114.232]: 451 4.3.5 Server configuration problem; from=<pvhuu90@gmail.com> to=<huupv@devopsskills.info> proto=ESMTP helo=<HuuPV> How I do it.... Step 1: Increase System Resources Zimbra requires adequate resources to run efficiently, especially for medium to large-scale systems. Insufficient RAM or CPU can lead to server errors, including the 451 4.3.5 configuration problem. Recommended Configuration: RAM: ≥ 16GB CPU: ≥ 8 cores (for Zimbra MTA system) Ensure your Zimbra system is provisioned with these or higher specifications to handle the load. ...

Introduction Zimbra Collaboration Suite is a popular email and collaboration platform known for its flexibility and robust features. Managing a large number of email accounts can be a tedious task, especially in enterprise environments. Thankfully, Zimbra provides the ability to create multiple accounts using a CSV file, simplifying the process and saving valuable time. This guide walks you through everything you need to know about creating Zimbra accounts with a CSV file, from setup to advanced configurations. Why Use a CSV File for Zimbra Account Creation? Creating Zimbra accounts manually is manageable for small-scale needs, but for larger organizations, efficiency is crucial. Here are the main advantages of using a CSV file: Time Efficiency : Batch processing saves significant time compared to manual entry. Accuracy : Reduces errors by predefining account details in a structured format. Scalability : Easily handles the creation of hundreds or thousands of accounts. Prerequisites Be...

Introduction Zimbra Collaboration Suite (ZCS) is a powerful platform for email and collaboration solutions, widely adopted by organizations of all sizes. Whether you're managing a small team or an enterprise, creating multiple accounts efficiently is a crucial task. In this guide, we’ll explore the process of creating multiple accounts in Zimbra, including practical examples and best practices to optimize your workflow. Why Create Multiple Accounts in Zimbra? Benefits of Multiple Account Creation Efficient User Management : Simplifies onboarding for teams. Centralized Control : Maintains consistent settings across users. Automation Potential : Saves time and reduces manual errors. Getting Started: Prerequisites Before diving into the process, ensure the following: Zimbra Admin Console Access : Admin credentials are required. CSV File : A formatted CSV file for bulk account creation. Command-Line Knowledge : Basic familiarity with Linux commands. Step-by-Step Guide Creating Multip...