Linux Magazine的March 2021目录

According to DistroWatch, 274 Linux distributions are active [1]. However, that number is misleading. Many distributions are heavily based on other distros, with only minor variations such as software selection or the intended audience. Many distributions, too, are dependent on a major distro’s repositories. By contrast, Arch Linux, since its founding in March 2002, has gained a reputation for doing things its own way, according to a well-defined set of principles that appeals to users who prefer simplicity. Recently, I sent questions to Arch Linux Leader Levente Polyak, who consulted with the distribution’s core developers to provide answers. Arch was founded by Judd Vinet, who was lead programmer until 2007. According to the Arch team, Vinet was inspired by two distributions: CRUX [2] and PLD [3]. However, while he considered…

Vulnerabilities in the kernel are always ugly, but since the Linux kernel is a very complex piece of software, admins have to come up with a strategy to deal with them. Fortunately, patches are often available shortly after the discovery of a vulnerability, but the application and the subsequent reboot will lead to an – admittedly usually short – period of unavailability of the system. For Ubuntu systems, distributor Canonical has developed a very easy-to-use live patching system, Livepatch. It patches the kernel without requiring a reboot. This helps the admin sleep more soundly, and the system reboot can be skipped or postponed to a more convenient time, such as a scheduled maintenance window. To use Livepatch, you need an Ubuntu One account, which you create on https://auth.livepatch.canonical.com (Figure 1).…

Linux is considered a very secure operating system for computers of all kinds. Realistically, however, even Linux is not immune to vulnerabilities and malware, which is why you can find a large number of tools in the package sources of Linux derivatives to help scan for vulnerabilities. However, these tools tend to focus on specific weaknesses and narrowly defined attack scenarios by only analyzing a computer system for individual potential security problems. With the checksecurity tool collection, on the other hand, you can automatically check Ubuntu and Debian systems [1] and their derivatives for multiple potential basic security flaws or anomalies. Concept Checksecurity consists of a number of plugins, each of which you then customize in a configuration file. The corresponding files are in text format, so a simple editor…

Stars, such as our sun, go through dramatic changes: From an initial particle cloud 4.5 billion years ago full of gravitational potential energy, to its transformation via thermal energy, to its current main sequence state. From here, the sun will potentially become a red giant, a white dwarf, and then finally a black dwarf, a process that could take another 5 billion years. But even in two years, things can change. A new solar minimum, powerful solar flares, and coronal mass ejections have all occurred over the last couple of years. But there have been other developments over that period that are almost as significant; for one, there’s a new version of KStars, one of the best tools for exploring the solar system and beyond from your humble Linux box.…

A month rarely goes by without a new CPU monitoring tool being created. But network monitoring, by comparison, suffers from a lack of decent tools for ordinary users. Ntop is a good high-level tool, and Wireshark is deep and complex, but there’s very little in-between the two, and this is where pktvisor could help. Pktvisor is roughly analogous to Top, but it deals with network packets instead of CPU usage. This tool lists, categorizes, sorts, and highlights the quantity and type of packets as they’re consumed or produced by various processes on your system or network. One possible negative is that its default installation is via a Docker container. This does have lots of understandable advantages when you want to install on a cloud instance, or without making local network…

Sauerbraten is an old-school first person shooter (FPS) that’s also really old. The previous major release was in 2013. Since then it has been languishing on Source-Forge. The game itself offers the usual fare of reflex-fast baddy blasting through everything from dark Medieval corridors to tropical islands in the sky. There’s also the usual array of weapons, from shotguns to sniper rifles and era-defining heavy metal music. You can play capture the flag and team tactics, among a huge variety of other modes, and you can spawn bots if you’d rather practice against your CPU than other people’s brains. This is all what you’d expect from such a game. But there are some original elements too, such as being able to edit the map in-game, and the almost 200 new…

Writing a game from scratch is hard, and that’s why nobody does it anymore. Game creators instead use “engines” that combine a framework and a comprehensive set of tools that let you skip the drudgery and get to the creative parts right away. Godot [1] is one of the most popular free and open source game engines, and, after a couple of weeks playing with it, I can see why. The Concept One of Godot’s creators, Juan “reduz” Linietsky, stated that the name “Godot” is a reference to the homonymous gentleman in Samuel Beckett’s play. Godot, in the play, never arrives and, in a similar manner, Linietsky says the Godot game engine will never be entirely finished, as it can always be improved and expanded. After six years of active…

So you think you know open source? Just the fact that you are reading this page means that what you probably know is Linux. This month, the DVD provides a glimpse into another corner of open source – the world of BSD. Like Linux, BSD varieties are free operating systems that are Unix descendants. However, they are released under the permissive BSD licenses rather than the copyleft licenses that dominate Linux. You will also find many other differences, despite the similar underlying structures. FreeBSD 12.2 64 First released in 1992, FreeBSD is the most popular version of BSD, especially for servers. Those coming from Linux will find many details different, such as the device naming system, as well as many commands and applications. More importantly, FreeBSD has never passed through…

Stream processing, also known as data stream processing, has been around since the early 1970s, but it has seen a big resurgence of interest in recent years. To understand why stream processing is on the rise, first consider how a conventional program processes data. Traditional software reads a chunk of data all at once and then performs operations on it. This batch technique is fine for certain types of problems, but in other use cases, it is quite limiting – especially in the modern era of parallel processing and big data. Stream processing instead envisions the data as a continuous flow. New events are processed as they occur. You can envision the program as something like a factory assembly line – a stream of incoming data is analyzed, manipulated, and…

Looking back at 2020, it’s impossible not to talk about the pandemic or the economy. However, free software businesses and communities suffered less than many organizations this year, for the simple reason that many of the precautions that others scrambled to put in place have been standard practice in free software for decades. For example, when everyone was advised to work from home, many Ubuntu employees [1] were doing so already. Aside from a surge of interest in videoconferencing, the pandemic has been largely business as usual in free software. For that reason, a thorough summary of trends and events in free software during 2020 is impossible. As usual, too much was happening. However, here is my pick of the key events of 2020 at every level from the corporate…

Both the chroot command and a container are ways to isolate parts of a system. However, their methods are quite different. While a container is a form of virtualization with its own allocated resources, chroot is a way to limit a user account’s access to the parts of the directory tree by – as the name of the command implies – changing its root directory. The result is what is known as a chroot or, sometimes, a chroot jail, which draws on the larger system’s resources as needed. The result is more economical, if less trendy than containers, but it is difficult to set up. Fortunately most distros include jailkit [1], a collection of utilities that helps to automate setup and configuration. Contrary to widespread misinformation, a chroot is not…

Recently, I was working on a project on Nvidia’s Jetson Nano platform [1]. The project required me to build certain kernel drivers. Of course, I looked through the requisite driver makefiles to determine which CONFIG options needed to be enabled. However, when I ran make menuconfig, I noticed that, while I could search through the kernel for the particular CONFIG option, I couldn’t actually navigate to the menu to enable it. Furthermore, when I tried to modify tegra_ defconfig, which is the standard kernel configuration for Nvidia platforms, to include the required CONFIG option, the kernel simply ignored it. Unfortunately, the kernel gave no indication as to why the specific CONFIG option was ignored. While I ultimately determined that there was another CONFIG option that needed to be enabled (which…

That there are so many note-taking applications is perhaps a reflection of how personal note taking can be. We all have our own proven methods and routines. But one of the best accepted ways of taking notes is by actually writing or drawing them, rather than typing them on a keyboard. The physical act of drawing something seems to help the brain with categorization and recall, whereas typing can be more passive. There are far fewer note-taking applications capable of working with this kind of sketch, but Xournal++ is one of them. Xournal++ has been designed first for written, rather than typed, note taking, which is also why there are versions for the web, Android, Chrome OS, and (imminently) iOS, alongside the GTK+ desktop version we’re looking at. The UI,…

One of the best things about Linux is that it’s easy to augment your distribution’s base functionality with whatever tools and utilities you need for your own specific hardware. It’s common to use the sensors package to monitor system temperatures and fan speeds, for example, or to install the thermal daemon, thermald, to control the fan speed across different temperature thresholds to save power or to maximize performance. While you can often monitor storage temperatures with these tools, neither will let you control how and when an external disk can be suspended to save both power and wear and tear on your hardware. But this is something you can do with hd-idle, a modern re-implementation of Christian Mueller’s hd-idle with some additional features. Hd-idle is a utility that navigates the…

Hex editors are cool. Even when you don’t know what you’re doing, they can be a thought-provoking tool to play with. Hex, or hexadecimal, is a number system that represents 16 decimal values starting with 0 as a single digit, with 0 to 9 followed by a, b, c, d, e, and f (for the double digit decimals 10 to 15). This is useful because computers typically process binary values in multiples of 16 bits, which are easily represented with a single 0 to f character in hexadecimal. This is what hex editors do, and they’re an acute reminder that despite all appearances, your computer really is just iterating over a set of instructions with a set of data. Even the humble xxd command, which simply creates a hexadecimal dump…

Whether you use CentOS for your servers or your desktop, the embroiled Linux distribution has recently found itself in a state of tumult. You’re probably wondering where to go now? If you’re not in the know, Red Hat has decided to end CentOS as it stands, in favor of the rolling release, CentOS Stream. This decision has placed a large number of the Linux community in fit of pique, looking for a new distribution to handle what CentOS handled with agility, security, and reliability. That’s where CloudLinux comes in. On December 15, 2020, the company whose goal is to increase the security, stability, and availability of Linux servers announced it was sponsoring Project Lenix, which will create a 1:1 binary compatible fork of Red Hat Enterprise Linux (starting with version…

Our modern world is increasingly dependent on continuous data streams that generate large volumes of data in real time. These streams might come from science experiments, weather stations, business applications, or sensors on a factory shop floor. Many of the software systems that interact with these data streams follow an architecture in which events drive individual components. Continuous data sources (producers) such as sensors trigger events, and various components (consumers) process them. Producers and consumers are decoupled using a middleware layer that handles the distribution of the data, usually in the form of a message broker. This approach reduces complexity, because any number of services can receive and process incoming data streams virtually simultaneously. This flexible architecture gives rise to a new generation of tools that provide users with an…

If the only protection between an attacker and a user account is a password, security-conscious administrators start to get nervous – and rightly so. Although strong passwords can be enforced, carelessness cannot be ruled out. Two-factor authentication (2FA) provides additional protection against unwanted visitors, even if a user chooses a weak password. While the user’s password remains as the first authentication factor, a six-digit numerical code with a limited validity period generated by a smartphone authenticator app adds a second factor. In this article, I will show how to require a one-time code at login (in addition to the user’s password) by creating an app on the user’s smartphone. This procedure was developed by the Initiative For Open Authentication (OATH) and has been an Internet Engineering Task Force (IETF) standard…

Traditional security mechanisms like Transport Layer Security (TLS) provide the ability to authenticate both sides of a direct session between two parties, and to encrypt the traffic passing over the authenticated session. For applications that fit into the footprint of the client/server architecture, TLS is a fine solution for authentication and encryption. However, as applications become more sophisticated, client/server applications are often challenged to maintain availability with a large number of clients. Middleware layers often serve as a means for providing more graceful scaling. The practice of adding layers to the application stack connecting communicating parties is called decoupling. Decoupled applications – applications that may contain components like message queues or brokers between the message sender and receiver – have been around for many years. Decoupled designs are now employed…

Hugin is a free and open source program that has been around for years. Up to now, it has mainly been used to create large panoramic images from a few – or even many – single images. If you use Hugin correctly, you can create good panoramic images very quickly. However, Hugin also supports other uses that include generating HDR images and computing super resolution images – large, extremely high-resolution images created by interpolation. Hugin also includes many advanced tools, for example, letting users determine the correction data for lenses (calibrate_lens_gui). The align_image_ stack command, which is used by many other programs to align images, is also part of the Hugin package. Hugin [1] was originally developed as a user interface for Panorama Tools, also known as PanoTools [2]. Later,…

As Linux users, we’re familiar with not being able to use the latest shiny Apple and Samsung devices with our computers, especially now that so many rely on companion smartphone apps to control their configurations. This can be difficult when devices such as Apple’s AirPods, or Samsung’s Galaxy Buds Live, are some of the best devices in their class. For the latter, however, we now have LiveBudsCLI, a brilliant open source tool that lets you control all aspects of your Samsung inear earbuds from the luxury of your Linux command line. Live-BudsCLI works with both Galaxy Buds Live and Galaxy Buds+. After first pairing your device in the normal Bluetooth way for your system, you need to run the earbuds -d command. This launches a background daemon that will monitor…

It’s always surprising just how many excellent and innovative audio production tools you find on Linux. As we’ve said many times before, they may not have the professional sheen of the commercial mainstays on macOS and Windows, but they make up for that in flexibility and rapid progress. Yabridge is one of the best examples of this. The “ya” in its name refers to the oft-used phrase “Yet Another,” and in this case, yabridge is “yet another way to use Windows VST plugins on Linux.” This is quite self-deprecating, because, while there are indeed a few projects that try to do the same thing, yabridge is the best. For the uninitiated, VST plugins are discrete audio instruments and effect-processing applications. There are thousands, from samplers and synthesizers to spring reverbs…

It’s difficult getting into trading stocks because it involves learning with real money. Even the free simulation sites are typically linked to real trading portals, which will then try to tempt you into their paid-for accounts after they’ve no doubt created a model for your behavior from the data you’ve provided them. TradeSim doesn’t have that problem because it’s the open source beginnings of a game you can play on your local machine, and it starts with importing a set of data you can use to test your instincts. The package includes access to Euro and GBP to USD currency databases from 2019 and 2020. They can be downloaded in-game, but also manually as an SQLite database from the project’s GitHub account. With these imported, you create a new simulation…