Linux Magazine的June 2021目录

Package managers differ from each other not only in terms of the package formats they use, but also in their execution speed. Developer Michael Stapelberg has been working on how to streamline package managers such as Debian’s Apt or Fedora’s DNF to make them faster. He has written blog posts on the subject, given talks, and created an experimental distribution, distri [1] to explore the problem. Distri is a minimal, command-line distribution for reviewing package management concepts in Linux. This is purely a feasibility study and is not suitable for production use. Distri seeks to be the simplest distribution that is still useful. Criticism of Debian Stapelberg, currently a Google developer, was a package maintainer at Debian from 2012 to 2019. Besides maintaining packages of Debian he wrote the i3…

Our world of web applications and fast, interactive mobile devices calls for the free exchange of data in easily accessible forms. Standard formats promote interoperability and minimize development time. Open formats also make it easy to import data into other applications. Over the years, several popular alternatives have emerged. CSV, XML, and YAML are well known and easy to adapt to different applications (see the box entitled “Comparing Formats” and Listings 1-3 for examples). One format that is used extensively for web applications, mobile applications, and even some conventional desktop tools is JavaScript Object Notation (JSON) [1]. JSON is wildly popular as a tool for passing information between web apps – for instance, it is currently the de facto standard for REST services – yet for many users, the details…

In a file manager, have you ever observed how newly created files by other applications immediately appear in the displayed directory and wondered how this works? As continuous querying of the filesystem is out of the question for performance reasons, these applications use the Linux filesystem’s inotify interface instead. Operating systems implement the mechanism in different ways: Linux uses inotify, the Mac uses kqueue, and Windows comes with an unpronounceable extra. Fortunately, the Go library fsnotify on GitHub abstracts this proliferation to create a simple interface. This means that programmers only need to write their applications once to cover all platforms. No Stress About 15 years ago, I wrote an article on this topic in my regular column [1]. At the time I used Perl, and the article relied on…

EdUBudgie Linux [1] is a distribution based on Ubuntu Budgie [2] but specifically tailored for use in high schools. I am an English teacher, and I put this project together with high school education in mind – although many first and second year university students may also find it suitable. I started with the standard Budgie offering and added or removed packages based on their applicability to high school education. The education-focused IT market is a crowded one, and in deciding how to build and market this distribution I carefully considered package selection, initial setup, post-install system administration, the learning curve needed, and finally performance and longevity. With all that in mind, I did make some compromises in the build that I will discuss shortly. I have intended EdUBudgie Linux…

Remarkably, it’s been eight years since Google closed its RSS Reader project. And yet, RSS survives and is more relevant now in the push information age than ever. Fortunately, there are still many websites that publish their own diminutive XML feeds containing brief synopses of their updates. Any RSS reader can then track and pull these updates, free of cookies and click-through advertising. Despite its age, RSS remains a refreshing alternative to the commercialization of the Internet, from sponsored newsletter placement and paid-fortweets, to GIFs as non-fungible tokens (NFTs). Which is why it’s brilliant to see another new RSS reader, NewsFlash, and a sign that RSS might be going through a small renaissance. News-Flash is a new, small, and beautifully designed RSS reader that makes RSS feel more like an…

Mapping special keys from your keyboard into meaningful Linux commands is a common problem that can be brilliantly solved by Key Mapper (above) or magical xmodmap incantations. But the inverse is also a common issue; mapping Linux keyboard commands to their macOS or Windows equivalents. This can help if you’re running macOS or Windows in a VM, in a remote desktop, or via a remote commandline session. It’s particularly noticeable when you’re using macOS, because it relies heavily on its special keys for fundamental functions such as copy and paste. This is where Kinto.sh can help. It’s a small Python script alongside a few configuration panels that can take over your keyboard and map those Linux special keys to macOS special keys, enabling you to invoke the same shortcuts regardless…

Technology has transformed education in unprecedented ways, from easy and free access to in-depth video tutorials and complete online educational courses, to group learning and one-on-one virtual coaching. But technology hasn’t been quite as successful at transforming the actual way that we learn, despite brave attempts from the likes of Khan Academy and Duolingo. Learning still requires hard work. There are, however, lots of tools that can help, and one of the best of them is Anki. Anki is an application that helps you create flashcard decks and train yourself from their contents. For a piece of software, this premise may not seem too adventurous, but Anki has been hugely successful already by helping students across the globe study for exams using their tablets, smartphones, and web browsers. It’s successful…

A well-known xkcd cartoon starts with 14 competing standards [1]. Someone resolves to simplify the situation by developing one standard that covers all the others. The result? Fifteen competing standards. The cartoon reflects a wry truth that has recently been illustrated in a proliferation of software installers that complicates matters for those who install cutting-edge applications. Increasingly, would-be users have to learn a new installer and install more software before they can get to the software they want to try. When Linux first became popular in the late 1990s, software installation often ended in what was known as “dependency hell,” in which users had to track down the correct version of each dependency and risked leaving a package half-installed. One way around this problem was to use static tarballs –…

In the early ’80s, Rogue, a game that would overhaul the gaming world, was released. According to Roguelike Gallery, Rogue first ran on a PDP-11 machine running Unix v6 [1]. Primitive by today’s standards, Rogue popularized the Roguelike genre despite not being the first game of its kind. Rogue’s influence can be seen in modern commercial titles. Rogue’s source code is still available, as are many games that pre-date Linux. In this article, I show how to set up a server to host antique terminal games. Why would you want to do this? Besides preserving a piece of history, playing these games is fun despite their age. In addition, running games on a specific server allows you to keep scoreboards, letting you compete against friends on a shared server. Last,…

Screenplays require a specific format and make special demands on the author. Unlike a novel, a screenplay virtually reduces the story to the dialogue. You’ll also need to use a special layout based on a fixed-width font and wide margins – a standardized format that makes it easier for production companies to estimate the length of the film. Rather than messing around with setting up this layout in a word processor, professionals use special programs, which may also include useful functions such as helping keep track of characters and locations. If you’re looking for these tools in a free application available on your Linux distribution, you won’t find many options, but one that may fit your needs is Kit Scenarist [1]. Installation Although the cross-platform software is currently not available…

It’s a cliche, but Audacity really is one of those flagship open source applications that many people simply couldn’t do their jobs without. It allows podcasters, community radio stations, and amateur musicians the world over to create serious, professional results without the serious outlay commercial applications often require, none of which work natively on Linux anyway (except BitWig!). Which is why, despite its modest set of new features, the release of Audacity 3.0 is still significant. We’re simply grateful that the application continues to be developed, and we’re particularly excited by the news that work is being undertaken to overhaul the outdated UI that has held it back from properly integrating with modern desktops, even if that isn’t in this release. But this isn’t a reason to discount version 3.0.…

Spotify has become hugely successful. While there is a semi-official Linux client, it has always felt more like a hobby project than a first class citizen. It’s perpetually in beta and seldom has feature parity with the Windows or macOS versions. What’s worse is that it’s built on Electron, making it resource hungry and not particularly well integrated into the Linux desktop and its various window managers. It’s hard to use with a tiling window manager, for example. Fortunately, and to Spotify’s credit, third-party libraries have been developed that can access Spotify’s API and consequently allow alternative clients to be easily developed. The best of these is a background daemon called spotifyd, and there are now several clients that take advantage of this. The brilliant spotify-qt is one of them.…

There can be few oldschool Amiga types who didn’t play the classic Cannon Fodder. It was a remarkable game with an emotional and strategic complexity that belied its cute graphics and sardonic portrayal of war. Created by Sensible Software in the UK, and using the same tiny pixelated character sprites and top-down view as their insanely addictive Sensible Soccer, Cannon Fodder saw you control a squad of soldiers as they made their way through various terrains. It was controlled by the mouse, with a left-click setting a target destination and the right-click reserved for shooting. This meant your squad could move in one direction and shoot in another at the same time. The terrain was also cleverly designed to hide your opponents and to offer various kinds of cover. You…

Our minds work in mysterious ways. No matter how hard we try, we cannot always direct our thoughts in an ordered succession of steps, ignoring distractions. It can be equally hard to spot useful links between apparently unrelated pieces of data or to remember all the relevant information connected to a particular issue. Software programs attempting to make these processes more efficient can take many forms, from desktop or personal “wikis,” to “knowledge bases,” or “mind mappers.” But their general goal is the same: to help users document and connect their ideas as efficiently as possible. This tutorial describes one of these tools, the basic version of Obsidian [1], which runs on Linux and other platforms and is free of charge for personal and educational use. Main Features Obsidian, describes…

For over 20 years, Knoppix has been the premier portable operating system and rescue disk for Linux users. Although its packages are drawn from the Debian repositories, and contributors add to its hardware support, the bulk of the work on the distribution is done by German electrical engineer Klaus Knopper (Figure 1), an independent consultant and instructor at the Kaiserslautern University of Applied Sciences. Over the years, Knoppix’s hardware support has increased, features have been added and dropped, and its original purposes have been joined by ADRIANE (Audio Desktop Reference Implementation and Networking Environment), a desktop designed for the sight impaired with input from Klaus’s wife, Adriane Knopper (Figure 2). All of which shows how this passion project is evolving with the times and is as important as ever. “When…

TCP/IP is at the heart of the Internet, and the Transport layer is at the heart of TCP/IP. The Transport layer is responsible for end-to-end connections between the sender and receiver over a TCP/IP network. The two most common Transport layer protocols are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). Nearly all Internet traffic uses either TCP or UDP. TCP is connection-oriented, which means that a connection between the client and server is established before data can be sent. The TCP protocol provides reliable ordering and error-checked delivery. UDP is a connectionless protocol, which means it provides only minimal information and has no handshaking procedure. UDP does not offer a guarantee of ordering or delivery. Of course, the brevity of UDP makes it much faster than the steady…

When you need to manage large numbers of devices, there is no avoiding centralized data management. In the simplest case, this can be a wiki, with one entry per system. This will include, for example, the date of purchase, the length of the warranty period or maintenance contract, any repairs that have already been made, and the rack number where the device is installed (finding the hardware in a larger data center can be time-consuming). I then encode the URL of the wiki entry as a barcode or QR code, print it on self-adhesive film, and stick it on the device. I generate the codes for this with Zint [1]. Many distributions have Zint on board; if not, it is quickly compiled from the GitHub repository. You must have libpng…

As someone who uses an older MacBook Pro with Linux natively installed, it’s imperative that Apple’s special Control and Option keys are mapped to work with Linux effectively. This is a rather arcane twostep process, first because you run the ancient xv command to divine the raw keycodes for those keys, and second because you enter those keycodes into an equally ancient xmodmap file to map those raw keycodes into key presses. As the x in both tools suggest, this process is unlikely to work with Wayland. Key Mapper is a Python application with a modern GTK+ front end that does all this easily and adds the ability to map buttons and keys from almost any input device. This is the clever part, because input devices can include joysticks and…

One of Mozilla’s best projects for Firefox was Send, an inbuilt mechanism for sharing files securely and anonymously with other users. It was incredibly convenient if you wanted to send a document to a family member, or share even a large file with a group of friends. Unfortunately, this convenience came at a cost – both in terms of the interim storage used by Mozilla and because “some abusive users were beginning to use Send to ship malware and conduct spear phishing attacks.” Send development stopped, and the service was discontinued. Of course, there have always been alternatives, and one of our favorites is a command-line tool called Magic-Wormhole, which works brilliantly even across networks. But it does require both the sender and the receiver to use the command line,…

Thanks to their high frame rates and realistic physics, virtual pinball games running on modern hardware are a long way from the early Amiga 2D titles that started the genre. You can even find entire arcades in virtual reality along with properly licensed recreations of dozens of actual pinball games from the ‘70s, ‘80s, and ‘90s. Developers have lovingly written code to emulate both the circuits of the solid state era and the CPUs of the digital era that replaced it, and players have even attached low latency switches and large screens to help play these emulations at their best. You can do something similar with Emilia Pinball, an open source pinball environment designed to be run on an embedded device with OpenGL acceleration. Even without a specific device, the…