How to flush the DNS cache in Debian GNU/Linux?

If using systemd-resolved as your DNS resolver (i.e. the hosts line of your /etc/nsswitch.conf file includes the word resolve and/or /etc/resolv.conf contains the line nameserver 127.0.0.53), then this command will flush its cache:

sudo systemd-resolve --flush-caches

A newer version of this command seems to be:

sudo resolvectl flush-caches

How to convert WMV to MP4

You can use FFmpeg (a free command-line tool for Mac, Linux and Windows) to encode WMV to MP4. Here is an example syntax:

ffmpeg -i input.wmv -c:v libx264 -crf 23 -c:a aac -q:a 100 output.mp4

This will encode the video to H.264 video and AAC audio, using the default quality. To change the quality for the video, use a different CRF value, where lower means better, e.g. 20 or 18. For audio, 100% is the default quality. Increase the value for better quality.

For the AppleTV specifically, this is what Apple says it supports:

H.264 video up to 1080p, 30 frames per second, High or Main Profile level 4.0 or lower, Baseline profile level 3.0 or lower with AAC-LC audio up to 160 kbit/s per channel, 48 kHz, stereo audio in .m4v, .mp4, and .mov file formats

So, you could use the following command to force the 30 Hz frame rate and High profile:

ffmpeg -i input.wmv -c:v libx264 -crf 23 -profile:v high -r 30 -c:a aac -q:a 100 -ar 48000 output.mp4

How to install SSH2 extension for PHP 7.4

If You have an error like: Call to undefined function ssh2_connect() that’s mean that in your PHP not installed ssh2 extension.

Install this extension is very simple, in Ubuntu Linux or other Debian based distribution just use the command:

sudo apt install php7.4-ssh2

This command will install ssh2 extension to Your PHP 7.4. If you use other PHP version, just change number in this command to Your version.

Install LAMP server on Ubuntu

All the components of the LAMP server are available to install using the default system repository of Ubuntu. Hence, we can configure the environment without adding an extra repository. However, before moving forward, just run the system update command to ensure the system rebuilds the APT package index cache.

sudo apt update

Install Lamp server

We can install LAMP server components one by one on our Ubuntu system. However, it is a time-consuming process, hence to make it short here we are using a single command. That will not only install the LAMP server but also enable and start all the required services.

sudo apt install lamp-server^ php

The above command will select all the required packages to set up Apache, MySQL, and PHP on your system.

Uninstall the LAMP Server

Well, when it comes to uninstalling the LAMP server completely from your Ubuntu system, we can use the given command:

sudo apt autoremove --purge apache2* mysql-server* php*

How to Convert PNG, JPEG to WebP in Linux?

Webp is an open-source image format in Linux which supports lossless and lossy compression for images on the web.

One of the best practices to optimize the website performance is using compressed images.

This article will cover how to use webp image format for creating compressed and quality images for the website.

Installation

The webp package is already available in the official ubuntu repositories. Run the command below to update the Ubuntu repository to the latest index and install webp package.

sudo apt install webp

Converting image to webp format

Using the cwebp tool, an image can be converted into webp format. Run the cwebp command with option -q to define the quality of image and -o to define the output file.

In this example, I have used image file linux.png and linux.jpeg file to convert in webp format. You can choose your image name accordingly.

cwebp -q 60 linux.png -o linux.webp
cwebp -q 60 linux.jpeg -o linux1.webp

Converting webp image to png and jpeg format

In the previous step, we converted jpeg and png images to webp using cwebp utility tool. Now we will use the dwebp tool to convert webp images into png and jpeg format.

Use the dwep command with the option -o to create png and jpeg image format from webp. In the example, image.webp is used for the conversion.

dwep image.webp -o image.png
dwep image.webp -o image.jpeg

How to disable window move with alt + left mouse button in XFCE

If you go to the Xfce menu and choose settings > settings manager > window manager tweaks > accessibility, you can select another key instead of alt to move the windows or choose none at all. This should be just what you want.

You can also use xfconf-query to set easy_click to none (or another key) on the command-line:

xfconf-query -c xfwm4 -p /general/easy_click -s none

In some programs, like Photoshop Alt + left mouse key used to modify some data and it is very important to disable window move with alt + left mouse button in XFCE for correct work of programs.