Linux MagazineApril 2020的目錄

A Chromecast [1] is a small USB dongle that lets you stream audio-visual content from a mobile device to your TV. Just attach Chromecast to your TV, and you can stream to the TV using an Android or other device that supports Google Cast technology. Google originally developed Chromecast to support streaming from Android phones, but the open source community has never been slow to grasp an opportunity. Cast to TV is a Gnome Shell extension that lets you send pictures, music, and video to a Chromecast-enabled TV from the Gnome desktop. And if you don’t happen to have a Chromecast device, use the Playercast app on a Raspberry Pi or other Linux computer to receive the stream and act as an interface to your TV. Cast to TV for…

The Kubuntu Focus [1] is a high-performance laptop outfitted and optimized for maximum compatibility with Kubuntu and its KDE desktop. The Focus, which is produced by the Kubuntu Council, Tuxedo Computers, and MindShare-Management Inc., is the brainchild of MindShareManagement CEO Mike Mikowski. I first heard about this initiative through my role as Councilor for the Kubuntu project. Mike had approached the council via former council member Ovidiu-Florin Bogdan, with whom I co-host the Kubuntu Kafe live stream meetup and podcast. The idea of the Focus is to provide a highly polished, high-performance laptop computer targeting workflows for web designers, developers, and professional creators. The goal is to offer a “Power out of the Box” experience beyond that of the PC and MacBook. Unboxing The unit arrived just two days before…

When it comes to managing Linux computers, two frequently used commands, rm (remove) and dd (disk dump), require special attention. These two very powerful tools are potentially destructive. If they are not used carefully, data can be very quickly lost. While rm has an integrated emergency brake for the root partition, dd overwrites specified partitions without asking, causing some users to interpret dd’s name as an acronym for “destroy data.” To prevent specifying the wrong partition (and the resulting data loss), graphical user interface (GUI) tools can be helpful for creating bootable distribution images on external media, such as USB sticks or SD cards. In addition to some distribution-specific solutions, these tools include UNetbootin [1], which is not supported by all distributions; Rufus [2], which is only available for Windows;…

Long before the first computers existed, sorting data occupied mankind. The German-American Herman Hollerith invented an electromechanical machine as early as 1890 that sorted punched cards into different exit shafts to speed up the evaluation of the US census of that era. And even today, computers continue to sort data – whether this be for a list of YouTube video suggestions, the top 100 charts in the music industry by sales figures, or the slowest queries against a MySQL database for performance analysis purposes. Listing 1: bubble.go Machines sort at amazing speeds with programs changing the order of arbitrarily formed data structures. Most of the time, they’re relying on a simple key as a sorting criterion, often an integer or a character string. This explains why classical reference works on…

AOL, ICQ, MSN – the list of these once extremely popular messengers could be extended considerably. Today they are consigned to internet history, although some online providers still try to sell especially short or easy to remember ICQ numbers for thousands of US dollars. But the world today uses WhatsApp. Over 1.5 billion users use this messenger, which Facebook acquired in 2014 for $19 billion [1]. Away from the mainstream, smaller messengers such as Wire, Signal, and Telegram have carved out a niche for themselves. At the top of the list of reasons why users choose one of these alternatives is the desire for more privacy. Most messengers require central servers in the background, and this, in turn, means registering with your email address or phone number. This is not…

A media center is a computer or computer-like system that plays multimedia content to a playback device. Many media centers are configured to stream media files (music, video, or images) to a home television set, but you can also use a media center to stream to a game console, mobile device, or computer. The FOSS universe includes several Linux distributions that are designed to serve in the media center role – including Kodi and LibreELEC – but some users consider these tools too complicated for a casual home environment. The complex functions of the common media center can overwhelm many users and often require advanced knowledge. If you are looking for a media server for your home network that sets up quickly, is immediately ready for operation, and streams content…

Apache Cassandra is an open source NoSQL distributed data-base that stores and manages large volumes of data on standard servers. Cloud providers use Cassandra for configurations with many data centers spread across global networks. The story of Apache Cassandra began in 2007 when Facebook engineers Prashant Malik and Avinash Lakshman developed a very early version for Facebook’s inbox search. The challenge was to store the data for huge datasets residing on hundreds of servers. A year later, Facebook released Cassandra on Google Code, making it an open source project. In 2009, it joined the Apache incubator, paving the way to it becoming a top-level Apache Foundation project. Since then, many well-known companies have implemented Cassandra or a commercial version (DataStax Enterprise), including Apple, Netflix, Twitter, Sony, eBay, Walmart, and FedEx.…

Imagine you have a directory with hundreds or even thousands of files (without uniform extensions) that you want to organize. Or maybe you want to know the last access date of a file for backup, forensics, or version management purposes. Instead of tediously clicking your way through the files in a graphical file manager, a shell script with the test command can help identify filesystem objects as well as provide additional information about the files. Determining File Type The file command provides information about a file’s contents (Figure 1). Because it tests for patterns in the content, file cannot be misled by file extensions (Figure 2). file gets its pattern information from the magic file /usr/share/misc/magic.mgc. For special cases, you can create your own magic file and pass it in…

If you are looking to collect data from the Internet for a personal database, your first stop is often a Google search. However, a search for mortgage rates can (in theory) return dozens of pages full of relevant images and data, as well as a lot of irrelevant content. You could visit every web page pulled up by your search and cut and paste the relevant data into your data-base. Or you could use a web scraper to automatically download and extract raw data from the web pages and reformat it into a table, graph, or spreadsheet on your computer. Not just big data professionals, but also small business owners, teachers, students, shoppers, or just curious people can use web scraping to do all manner of tasks from researching a…

The popular line on the Internet is that you need to trade away your privacy to participate in the messaging and social networking communities, but the world of free software is all about avoiding such traps. Jami is a messaging app backed by the famous GNU project that protects your privacy and does away with servers altogether. We’ll introduce you to Jami and help you get started with the joys of free communication. Also in this month’s issue, we compare the Krita and MyPaint graphics tools and describe how to build your own homegrown notification tool using Bash scripts.…

When it comes to an open source alternative to Photoshop, most people think of Gimp. However, Gimp isn’t the only raster graphics (aka bitmap) editor for Linux. For drawing and painting, users quickly realize that they need more than Gimp, including brushes, Wacom-style graphic tablet support, and artistic effects. Krita and MyPaint are two open source alternatives that are specifically designed for digital artists. Krita [1], once the black sheep of the KOffice bundle, has received a lot of attention as a standalone application. A prominent participant in the Google Summer of Code since 2008, it has grown into mature, production-ready software with paid developers. MyPaint [2] is a simpler, more basic drawing application with fewer features. However, simplicity can be a great advantage, attracting many talented artists, including David…

Systemd has replaced init in most distributions for several years. Yet for many users, it remains mostly unknown. One reason for this obscurity is that, to avoid confusion, distributions hide systemd with aliases to traditional commands. It is only when you look into the intricacies of systemctl, a systemd command that views and manages a system, that you begin to appreciate how farreaching systemd actually is. Like other init systems, systemd’s main purpose is to start and control services that must be started after the kernel – those that run in userland, as it is sometimes expressed. The difference is that systemctl’s controls extend to other parts of a system as well and are far more extensive than init’s or Upstart’s controls. systemctl carries out these tasks by acting upon…

Adapt the appearance of the GRUB boot menu, boot screen, and KDE splash screen The splash screen and other startup images are a familiar sight for any Linux distribution. Although the desktop background and color scheme can be quickly customized to suit your tastes, the GRUB boot menu (Figure 1) and the boot splash screen (Figure 2) are far more difficult to customize. This article describes how to modify and unify your system by changing the GRUB boot menu and the boot and KDE splash screens to fit your personal preferences. The following examples are based on openSUSE, but the procedures are similar for other Linux systems – especially KDE-based systems. Start with YaST If you’re working in openSUSE or another SUSE variant, you can use YaST to select a…