Introduction Learn how to change string content of a file using bash script arguments. This guide provides detailed steps and examples, from default values to custom arguments. Master shell scripting to dynamically update file content efficiently. Bash scripting is a versatile and powerful tool for automating tasks and managing system operations. One common requirement is changing specific string content in a file using arguments passed to a script. This guide will demonstrate how to achieve this with a bash script, covering both default values and custom arguments. By following this tutorial, you will enhance your scripting skills and be able to dynamically update file content efficiently. In this tutorial, how to change string content of file as arguments. I written  Bash script arguments from a file content as below: What is Bash Scripting? Bash scripting involves writing a series of commands in a text file to be executed by the Bash shell . It is widely used for automating repe...

Introduction Learn how to handle default values for arguments and optional input arguments in Bash scripts. This comprehensive guide covers everything from basic to advanced examples, ensuring you can write efficient and flexible scripts. Bash scripting is a powerful tool for automating tasks and managing systems. One essential aspect of writing efficient Bash scripts is handling arguments and providing default values. This ensures that your scripts can handle various scenarios without requiring mandatory inputs every time. In this article, we will explore how to handle default values for arguments and optional input arguments in Bash scripts, from basic to advanced examples. Understanding Bash Script Arguments What are Bash Script Arguments? Bash script arguments are parameters passed to a script at runtime. These arguments are used to provide input data to the script, making it dynamic and versatile. In Bash, arguments are accessed using the $ symbol followed by their position (e.g....

Introduction When managing web servers, it's common to encounter the need to reverse proxy through different web servers. Apache's mod_proxy module offers ProxyPass and ProxyPassReverse directives to handle these tasks. However, NGINX can be used as an alternative to Apache for reverse proxy needs due to its performance and configuration simplicity. This article explores how to use NGINX to achieve similar functionality to Apache's ProxyPassReverse. NGINX Solution for Apache ProxyPassReverse Understanding Apache’s ProxyPassReverse The ProxyPassReverse directive in Apache adjusts the URLs in the HTTP headers sent from a reverse proxy. This is essential for maintaining session consistency when the backend server redirects responses. Apache configure <VirtualHost myhost:8888>     ServerName myhost     DocumentRoot /path/to/myapp/public     ProxyPass / http://myapp:8080/     ProxyPassReverse / http://myapp:8080/ ...

How to solve problem Openssl libssl.so.1.1 not found on your system such as centos, ubuntu. Installing openssl missing depens libssl.so.1.1 not found and libcrypto.so.1.1 not found. Openssl libssl.so.1.1 not found problem as below: [huupv@huupv ~]$ ldd /usr/bin/openssl     linux-vdso.so.1 (0x00007ffe185e6000)     libssl.so.1.1 => => not found     libcrypto.so.1.1 => => not found     libz.so.1 => /lib64/libz.so.1 (0x00007fc3ca6f4000)     libdl.so.2 => /lib64/libdl.so.2 (0x00007fc3ca4f0000)     libpthread.so.0 => /lib64/libpthread.so.0 (0x00007fc3ca2d2000)     libc.so.6 => /lib64/libc.so.6 (0x00007fc3c9f1c000)     /lib64/ld-linux-x86-64.so.2 (0x00007fc3cb2a1000) Openssl libssl.so.1.1 not found solve problem sudo ln -s /usr/local/lib64/libssl.so.1.1 /usr/lib64/libssl.so.1.1 sudo ln -s /usr/local/lib64/libcrypto.so.1.1 /usr/lib64/libcr...

Introduction The sed command in Linux is a powerful stream editor that allows users to filter and transform text in various ways. Whether you're working on system administration tasks or programming scripts, mastering sed can significantly improve your efficiency. In this tutorial, we will explore how to use sed with regex to manipulate lines within a file, focusing on printing lines from one point to another. This guide will help you understand the nuances of sed and its regex capabilities, ensuring you can handle text processing with ease. What is the sed Command? The sed (stream editor) command in Linux is used to perform basic text transformations on an input stream (a file or input from a pipeline). It is commonly used for text substitution, but it also allows you to select and manipulate lines, delete text, and more, using regex (regular expressions). Key Features of sed Text Substitution : Replace occurrences of a pattern with a specific string. Line Selection : Selec...

In this tutorial, I setup and Configure Postfix to use Gmail as a Mail Relay with 587 port. OS : Centos User : root Install postfix yum install postfix mailx cyrus-sasl cyrus-sasl-plain To configure postfix to use Gmail as a Mail Relay vi /etc/postfix/main.cf Add or modify the following as below: #To use smpt gmail with 587 port relayhost = [smtp.gmail.com]:587 smtp_use_tls = yes smtp_sasl_auth_enable = yes smtp_sasl_security_options = noanonymous smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd smtp_tls_CAfile = /etc/pki/tls/certs/ca-bundle.crt smtp_tls_security_level = encrypt # Location of CA certificates smtp_tls_CAfile = /etc/ssl/certs/ca-bundle.crt To configure Gmail authentication vi /etc/postfix/sasl_passwd Add the line as below: [smtp.gmail.com]:587    username@gmail.com:password Running commands as below: chmod 600 /etc/postfix/sasl_passwd chown root:root /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db postmap /etc/po...

In this tutorial, How to use nginx redirect all http to https. All traffic http redirect to https for your website. How to do it..... For example, nginx.conf file for your website     server {             listen 80;             listen [::]:80;             if ($host = www.huuphan.com) {                return 301 https://$host$request_uri;            }             if ($host = huuphan.com) {               return 301 https://$host$request_uri;             }          ...

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...