Block an IP address in firewall-cmd
Sometimes you need to block an IP address (or a range of IP addresses) from accessing your machine. In this case firewall-cmd can help you through these commands: And finally, if you decide to remove this rule, you can use these commands:
Change font in Moodle
If you have an academy and using moodle as an LMS is your choice, you may want to change default font of pages to a new one. In this article I am going to talk about a method to do so. First of all you have to choose which theme you wanna use (through Administration […]
Setup High Availability for HAProxy
To prevent service failure during disasters like server crash or so on, we have to find Single Point of Failure components and setup High Availability solutions for them. In this article I am going to define how to setup High Availability for HAProxy service. The structure of service would be something like below: In this […]
sudo without password
Typing password for sudo commands is an awful experience. So here’s what we should do to stop linux asking for password: 1. Backup the sudoers file: 2. Open the sudoers file for edit: 3. Edit sudoers file:
PHP: mysqli_connect(): The server requested authentication method unknown to the client [caching_sha2_password]
if you have these errors in your log file: It means that the server’s default authentication plugin is different from your client’s. So you have to change the user’s default authentication plugin by this command:
Hosting a Podcast
To start a new podcast, you have to generate a feed in XML format. This feed should contain metadata about the podcast and its episodes including a tag that point to link of uploaded audio file of episode. So, at least, you should have these items: To upload audio files you can choose one of […]
Fedora 33: Problem with Broadcom Wifi Device
I am using Fedora workstation as my main OS on my laptop for many years, but usually I face a problem with my wifi device when I try to update my OS or change it. So, here is a solution to fix the problem: First, you have to determine your wifi device model by this […]
How to make Apache HTTPD Web Server more secure
There are some known security issues that can make an Apache HTTPD Web Server insecure. If using Apache HTTPD as a web service is your approach, then you should scan your web server in first step. There are many tools to scan a web server. here we will use NIKTO. Nikto is a free tool […]
One way to Prevent DDOS attacks in WordPress
If you scan your WordPress site with wpscan tool, you would see a message like this: It means that a hacker can generate a DDOS attack on your host using this URL, cause this URL return a blank page and a 200 HTML Response Code. Also, this script will use a considerable amount of RAM […]
Connection Encryption in Oracle Database
To encrypt connections between client and database server you have to set some parameters in sqlnet.ora file ($ORACLE_HOME/network/admin/sqlnet.ora) of server and client (you have to install oracle client on the client): server side: client side: the ENCRYPTION_CLIENT parameter can have one of these values: ACCEPTED : The client or server will allow both encrypted and […]