What is an operating system?

An operating system (OS) is the Application Which, after being initially loaded into the computer by a boot program, oversees all the other application programs in a computer. The application programs make use of the working system by making Furthermore, users can interact directly with the operating system Via a user interface like a command line or a graphical user interface (GUI).

9 Popular Mobile Operating Systems

Android OS (Google Inc.) ...
2. Bada (Samsung Electronics) ...
BlackBerry OS (Research In Motion) ...
iPhone OS / iOS (Apple) ...
MeeGo OS (Nokia and Intel) ...
Palm OS (Garnet OS) ...
Symbian OS (Nokia) ...
webOS (Palm/HP) ...

Types of operating systems.

Operating systems normally include pre-loaded on almost any Computer you purchase. Many men and women use the operating system which comes with their computer, however it is possible to update or perhaps alter operating systems. The three most frequent operating systems for personal computers are Microsoft Windows, macOS, and Linux. A GUI enables you to use your mouse to click on icons, switches , and menus, and that which is clearly displayed on the display by means of a combo of images and text. Each operating system's GUI includes a different feel and look, so if you Switch to another operating system it might appear unfamiliar at first. However, modern operating systems have been made to be effortless to utilize , and the majority of the fundamental principles are exactly the same.

Microsoft established the Windows operating platform at the mid-1980s. There have been a number of distinct variants of Windows, but the latest ones are Windows 10 (published in 2015), Windows 8 (2012), Windows 7 (2009), along with Windows Vista (2007). Windows includes pre-loaded on many new PCs, which helps to ensure it is the hottest operating system on the planet.
Microsoft Windows
Microsoft established the Windows operating platform at the mid-1980s. There have been a number of distinct variants of Windows, but the latest ones are Windows 10 (published in 2015), Windows 8 (2012), Windows 7 (2009), along with Windows Vista (2007). Windows includes pre-loaded on many new PCs, which helps to ensure it is the hottest operating system on the planet.
MacOS (formerly called OS X) is a Lineup of operating systems made by Apple. It comes preloaded on all Macintosh computers, or Macs. A number of the specific models include Mojave (published in 2018), High Sierra (2017), and Sierra (2016). Based on StatCounter Global Stats, macOS users accounts for significantly less than 10 percent of international functioning systems--considerably lower than the percent of Windows users (greater than 80 percent ). 1 reason behind this is that Apple computers have a tendency to be costlier. But a lot of individuals do prefer the appearance and feel of macOS over Windows.
macOS
MacOS (formerly called OS X) is a Lineup of operating systems made by Apple. It comes preloaded on all Macintosh computers, or Macs. A number of the specific models include Mojave (published in 2018), High Sierra (2017), and Sierra (2016). Based on StatCounter Global Stats, macOS users accounts for significantly less than 10 percent of international functioning systems--considerably lower than the percent of Windows users (greater than 80 percent ). 1 reason behind this is that Apple computers have a tendency to be costlier. But a lot of individuals do prefer the appearance and feel of macOS over Windows.
Linux (pronounced LINN-ux) is a household of open-source operating systems, so they may be altered and distributed by all around the globe. This differs from proprietary program such as Windows, which may only be altered by the organization that owns it. The benefits of Linux are that it's free, and there are several different distributions or variations you may select from. Based on StatCounter Global Stats, Linux users accounts for under 2 percent of international functioning systems. But most servers run Linux since it's relatively simple to personalize.
Linux
Linux (pronounced LINN-ux) is a household of open-source operating systems, so they may be altered and distributed by all around the globe. This differs from proprietary program such as Windows, which may only be altered by the organization that owns it. The benefits of Linux are that it's free, and there are several different distributions or variations you may select from. Based on StatCounter Global Stats, Linux users accounts for under 2 percent of international functioning systems. But most servers run Linux since it's relatively simple to personalize.
The operating systems we have been speaking about so much were created to operate on desktop and notebook computers. Mobile apparatus like telephones , tablets , and MP3 players Are distinct from desktop and notebook computers, so that they run operating systems that have been designed especially for mobile devices. From the screenshot below, you can view iOS running in an iPad. Operating systems for mobile devices normally are not as fully featured As those created for desktop and notebook computers, and they are not capable to Run each the exact same software. But, you can still perform a Great Deal of things Together, like watch videos, browse the net, manage your calendarand play games.
Operating systems for mobile devices
The operating systems we have been speaking about so much were created to operate on desktop and notebook computers. Mobile apparatus like telephones , tablets , and MP3 players Are distinct from desktop and notebook computers, so that they run operating systems that have been designed especially for mobile devices. From the screenshot below, you can view iOS running in an iPad. Operating systems for mobile devices normally are not as fully featured As those created for desktop and notebook computers, and they are not capable to Run each the exact same software. But, you can still perform a Great Deal of things Together, like watch videos, browse the net, manage your calendarand play games.
Hey everyone and welcome back to the second and final part of this tutorial series where we explore the intricacies of Apple’s MusicKit by building our very own music player in SwiftUI that can stream songs from our Apple Music account. If you haven’t read Part 1, you can do that here. In the last tutorial, we looked at how to create a MusicKit Identifier for our Apple Developer account, created a JSON Web Token private key, and we were able to successfully make web requests to the Apple Music API. At the end of the tutorial, we also built […]

Feature Flags can improve your continuous integration process in a number of ways. This post will focus on how CloudBees Feature Flags can help improve your developer productivity and shorten the feedback loop with the Flag Override view for frontend validation.  It includes Javascript in examples, but the override view can be used in all available platforms. The flag override view is a lightweight UI element that is very useful for debugging purposes. This override view exposes the current status for each flag set by developers and allows users to override these flags. All this is accomplished from within a handy popup in […]

While I’ve introduced you quite a number of new features announced in WWDC 2020. Let’s step back a bit and check out a useful framework introduced in WWDC 2019. At first glance, it does not look as significant or important as other frameworks, however it consists of a really useful tool when it is needed. That is the LinkPresentation framework, and it provides a handful of built-in functionalities that makes presenting rich links in apps a really simple and straightforward process. LinkPresentation framework contains mechanisms that parse the website behind a link and fetch metadata necessary in order to display […]

macOS developers will most likely be faced with the requirement to build an installer for apps they want to — or must — distribute outside of the Mac App Store (MAS). There is also substantial economic incentive to explore macOS development targeting sales outside of the MAS. In this tutorial, I’ll be explaining how to use Packages, by far one of the most popular tools for developing macOS app installers. It is used by macOS developers worldwide. I’ll provide step-by-step instructions, including many screenshots, walking you through the entire process of building installers. Very importantly, Packages is freeware. A 2019 […]

WWDC 2020 was finished just a few days ago under unprecedented conditions for first time. Virtually, all developers around the globe had the chance for a seat in the front row, being able to learn about all new features and improvements that Apple had to announce this year right at the moment they were becoming available. As always, lots of new stuff and great advancements were introduced, and once again everybody has got really excited and eager to try many new things out. This post is dedicated to the base that makes everything else real; Xcode and Swift. The first […]

The first version of SwiftUI doesn’t come with a native UI component for multiline text field. For multiline input, you can wrap a UITextView from the UIKit framework and make it available to your SwiftUI project by adopting the UIViewRepresentable protocol. We have written a detailed tutorial on the implementationg, showing you how to create a multiline text field in SwiftUI. In iOS 14, which is expected to be released in late Sep, Apple introduced a new component called TextEditor for the SwiftUI framework. This TextEditor enables developers to display and edit multiline text in your apps. In this tutorial, […]

swiftui-outline-view-ios14SwiftUI list is very similar to UITableView in UIKit. In the first release of SwiftUI, Apple’s engineers already made creating list view construction a breeze. You do not need to create a prototype cell and there is no delegate/data source protocol. With just a few lines of code, you can build a list view with custom cells. In iOS 14, Apple continued to improve the List view and introduce several new features. In this tutorial, we will show you how to build an expandable list / outline view and explore the inset grouped list style. Building an Expandable List View […]

swiftui-grid-layout-lazyvgridThe initial release of SwiftUI didn’t come with a native collection view. You can either build your own solution or use third party libraries. In this year’s WWDC, Apple introduced tons of new features for the SwiftUI framework. One of them is to address the need of implementing grid views. SwiftUI now provides developers two new UI components called LazyVGrid and LazyHGrid. One is for creating vertical grid and the other is for horizontal grid. The word Lazy, as mentioned by Apple, means that the grid view does not create items until they are needed. In this tutorial, I will […]

Did you know that a macOS app can read and write outside of its container when sandboxed? Did you know that a non-sandboxed macOS app has no container? Were you aware that you can sell and distribute non-sandboxed macOS apps without using the Mac App Store? Since the focus of most Apple development seems concentrated on iOS, many developers probably take the sandbox for granted. Some might not even be fully aware of the sandbox’s existence, especially in the case of iOS where all apps must be sandboxed. By ignoring the sandbox — and possibly macOS development entirely — developers […]

Earlier, we explored the use of UIViewRepresentable and show you how to integrate UITextView into a SwiftUI project. While you can use the UIViewRepresentable protocol to wrap a UIKit view, but how about a view controller? You probably need to use camera or access the user’s photo library in your app. So, how can use integrate the UIImagePickerController class into your SwiftUI view? In this tutorial, we will walk you through the integration by using the UIViewControllerRepresentable protocol. It’s very similar to the UIViewRepresentable protocol, but UIViewControllerRepresentable is designed for wrapping a UIKit view controller. If you have already read […]

One of the most common tasks that iOS -and not only- developers are called to perform in their programming endeavours is fetching and managing remote images that should be displayed to an app. For instance, suppose that you’re building the next great messaging application where obviously users have contacts. Those contacts have avatar images residing to a server. When users connect to the app then avatars must be downloaded in order to be used by the app. Or, another example, think of an app that manages the event of a worldwide convention, and among its features is the list of […]

Since the advent of OS X Mojave and especially Catalina and the requirement for app notarization, some of us old-time macOS developers are concerned that Apple will pull the plug on the apps that we distribute ourselves. Many of you have downloaded and installed macOS software directly from websites, i.e., not from the Mac App Store. Have you ever really considered it? You can’t download an iOS app outside of the App Store. Yes, I know about the Apple Developer Enterprise Program, but it only “allows large organizations to develop and deploy proprietary, internal-use apps to their employees.” How many […]

Welcome to another macOS tutorial! In this post we are about to learn how to create a macOS application that belongs to a unique category of apps; a category that is quite common but also quite important, and contains a large number of existing and new macOS apps. We are going to learn how to create a document based application. It would be pointless to try to give a definition about what a document based app is, as you can immediately get it; just think of the browser that you’re reading this post now, or Xcode, or even TextEdit app. […]

The List view in SwiftUI is very similar to the table view in UIKit. It is also designed for developers to present a list of items row by row. By default, each row of data is separated by a line separator. In UIKit, you can easily control the appearance and color of the line separator. Unfortunately, there is no official way to remove line separators in SwiftUI. That said, we can make use of the UIKit API to tweak the line separator of the List view in SwiftUI. In this article, we will show you how this can be done. […]

I enjoy so much working with the SwiftUI framework. Like most new frameworks, however, one drawback is that it doesn’t come with all UI controls which are available in UIKit. For example, you can’t find a SwiftUI counterpart of text view. Thankfully, Apple provided a protocol called UIViewRepresentable that allows you easily wrap a UIView and make it available to your SwiftUI project. In this article, we will show you how to create a text view by wrapping the UITextView class from UIKit using UIViewRepresentable. Editor’s note: If you are new to SwiftUI, you can check out our introductory tutorial. […]

swiftui-search-barOne recent question I got is about the implementation of search bar in SwiftUI projects. Unlike UIKit, SwiftUI doesn’t come with a built-in control for search bar. You may use the UIViewRepresentable protocol to reuse UISearchBar in your SwiftUI project. However, as you look at the search bar, it’s not too difficult to build one entirely using SwiftUI. In this tutorial, let’s try to build a SwiftUI version of search bar. The figure below gives you an idea about the search bar we’re going to build. The look & feel is the same as that of UISearchBar in UIKit. We […]

Welcome to another programming tutorial in the Swift programming language! Today we we are going to talk about a topic that usually everybody knows something more or less, but it’s important for new developers in Swift to really understand what is all about and how it works. It’s quite often for the subject of our discussion not to receive the proper attention, so it’s either misused or not used at all. It’s a topic that the more someone advances in Swift, the more necessary it becomes in order to write better and clearer code. And that topic is about Access […]

Apple’s “app group” technology allows a collection of macOS (or iOS) apps from the same development team, developer, vendor, etc., to all communicate with each other, coordinate functionality, share resources, and minimize redundancies. Apple says this capability “allows the apps within the group to share Mach and POSIX semaphores and to use certain other IPC [interprocess communication] mechanisms among the group’s members.” A word of caution, though: I’ve experienced inconsistent and erratic behavior with macOS app groups, especially on OS X 10.15, Catalina. As explained below, you may have to experiment with the app group ID format. Nonetheless, this tutorial […]

At WWDC 2017, Apple announced MusicKit, a framework to help developers build apps that allow users to play Apple Music and their local music library. Unlike most frameworks like ARKit or CoreML, MusicKit cannot be added to your code with a simple import function. Rather, it’s a combination of the Apple Music API, the StoreKit framework, the MediaPlayer framework, and some other web-based technologies. You may be wondering why is this framework so difficult to integrate into your applications compared to other API and frameworks. This is because MusicKit was not only built to work on iOS devices, but Android […]

One of the most common operations macOS users perform and they are quite familiar with is drag and drop. On a daily basis we all drag things around when working on our Macs. We drag files, text, images, and many, many more. Dragging is a kind of action that users expect to find pretty much in every app on macOS, so supporting it in our apps is something we should seriously consider. A drag operation starts somewhere, so it has a source, and it ends somewhere, so there is a destination. Dragging source and destination can be either within the […]

swift-playgrounds-ipad-app“I only have an iPad. Can I use it to develop iOS apps?” This is one of the most common questions for beginners. My answer is always “No, you need a Mac to run Xcode for iOS app development.” “But how about Swift Playgrounds for iPad? Can I use the app to learn Swift and app development?” I believe you know Apple released an app called Swift Playgrounds for iPad. The first version of the iPad app was released in September 2016 with the aim to make it easy for everyone to learn the basics of programming, in particular, the […]

Earlier, we published a SwiftUI tutorial showing you how to create perspective text using the framework. It’s very much like Star Wars’ perspective text but without animation. This week, Priyans Brahmbhatt will teach you how to add animations to the perspective text. Since this article was built on the top of the perspective text tutorial, I highly recommend you to check it out first. We will start from where the previous tutorial ended. Let’s have a look at the code again: Animating the Text Using SwiftUI Before writing the code, let’s think about how we can achieve the animation. I […]

Welcome to a new and interesting enough programming tutorial! Swift is a rich-featured language and it couldn’t be missing a great feature such as the higher order functions. According to Wikipedia: In mathematics and computer science, a higher-order function is a function that does at least one of the following: – takes one or more functions as arguments (i.e. procedural parameters), – returns a function as its result. All other functions are first-order functions. From the practical point of view in real world programming, higher order functions consist all together of a great tool that we can only have benefits […]

If you’ve upgraded to Xcode 11.3 and you use Interface Builder to create the app UI, you may find it impossible to set the value of spacing constraints to zero. Just open Interface Builder and click “Add new constraints” to try it out. After you set one of the constraints to 0, it’ll automatically revert it back to standard. We got a number of emails from our readers asking about the issue. No worries. It’s not your fault, but a bug in Xcode 11.3. And, according to the release note of Xcode 11.4, the bug will soon be fixed: Fixed […]

vettery-adAre Mondays starting to feel like a drag? Did someone ask you to reset a random password? Beg you to connect them to the printer? Or perhaps your code just isn’t getting enough love, and you’re tackling the same bugs over and over, only to find…more of the same bugs. If you’re feeling less hurrah and a lot more blah, maybe it’s time for a big career change. Vettery is an online hiring marketplace that connects top developers, product managers, and user experience designers with inspiring companies. Once you’re accepted to Vettery, companies contact you directly and request interviews. Vettery’s […]

swift-json-codable-demo-appFirst, what’s JSON? JSON (short for JavaScript Object Notation) is a text-based, lightweight, and easy way for storing and exchanging data. It’s commonly used for representing structural data and data interchange in client-server applications, serving as an alternative to XML. A lot of the web services we use every day have JSON-based APIs. Most of the iOS apps, including Twitter, Facebook, and Flickr send data to their backend web services in JSON format. As an example, here is a JSON representation of a sample Movie object: As you can see, JSON formatted data is more human-readable and easier to parse […]

Hello readers! I’d like to start today by saying that this is a macOS programming tutorial that I wanted to write for a long time now. Not only because it’s extremely interesting, but also because we are going to meet a different kind of applications that one can build for the macOS operating system. However, most of the previous tutorials about macOS programming had to come first because some prior knowledge is required, but eventually here we are! We are just about to learn how to create status bar apps, or in other words, apps that live on the macOS […]

Welcome to a new tutorial where I’m going to show you a practical approach on how to create your own Swift packages. If you’re not familiar with that term, a Swift package wraps up code that can be reused in projects, to be shared with other developers, as well as to be added as a dependency to projects. Creating and managing Swift packages has been an integrated functionality in Xcode since version 11, and that makes dealing with them a fast and straightforward process. A Swift package is mainly composed by two parts: The source code which is the heart […]

Following the footsteps of IKEA and L’Oreal, businesses across verticals started dreaming up uses for augmented reality (AR) that could enhance the customer experience. This massive growth of AR-based business applications can be attributed to the ARKit launched by Apple.  “I do think that a significant portion of the population of developed countries, and eventually all countries, will have AR experiences every day, almost like eating three meals a day. It will become that much a part of you.” —Tim Cook Rightly so, millennial apps like Snapchat and Instagram have made AR a phenomenon. Borrowing from such app experiences, innovative […]

If you’ve been programming with SwiftUI before, you probably got a taste of building gestures with SwiftUI. You use the onTapGesture modifier to handle a user’s touch and provide a corresponding response. In this tutorial, let’s dive deeper to see how we work with various types of gestures in SwiftUI. The framework provides several built-in gestures such as the tap gesture we have used before. Other than that, DragGesture, MagnificationGesture, and LongPressGesture are some of the ready-to-use gestures. We will looking into a couple of them and see how we work with gestures in SwiftUI. On top of that, you […]

Welcome to a new tutorial where we are going to unfold another cool topic on macOS programming. Today we are going to meet an important control, really useful for displaying hiearchical data, the outline view. Outline view inherits from table view, so there are significant similarities to the way we handle both. Table views have been the topic of this previous post, and I strongly recommend you to read it before you go to this one if you haven’t done so. What makes outline views a unique control is that displayed data can be expanded and collapsed, just like the […]

If you’ve worked with UIKit before, the Text control in SwiftUI is very similar to UILabel in UIKit. It’s a view for you to display one or multiple lines of text. This Text control is non-editable but is useful for presenting read-only information on screen. For example, you want to present an on-screen message, you can use Text to implement it.  SwiftUI, Apple’s new declarative UI framework, has been officially released for around two months. If you still haven’t explored the framework, this tutorial is written for you. In this tutorial, I’ll show you how to work with Text to present information, customize it with your preferred color, and apply […]

Another macOS programming tutorial is here, and today we’re going to talk about a really interesting topic: Menus. Every macOS developer has to know about how to deal with menus, as they consist of a fundamental part on every application. Menus is the place where users access the app’s features and functionalities, and be sure that they always expect to find and use them. Menus are parted by menu items, where a menu item is the actual option that gets clicked. Menu items can have single keys or key combinations assigned to them, so users can have access to the […]

swiftui-bookWe have just launched our new book – Mastering SwiftUI. As introduced to you earlier, this book teaches you how to build UIs and iOS apps with Apple’s brand new UI framework. It is written for both beginners and developers having some experience with Swift programming. We will dive deep into the framework, explore the commonly used UI components, and teach you how to build complex layouts.  Animations play a key role in modern mobile apps. In this book, you will also learn various animation techniques and build some cool view animations.   After going through the basics, we will put together everything you […]

Hello folks! In a time where the App Store is full of apps, users have more than plenty of options to choose from. There is a lot of competition on all kind of apps, and users want to try them before they decide whether they like them or not. On the other hand, developers target on making some profit out of their published apps, but first they need to build an audience for that. Releasing an app as a paid one is not something that guarantees a financial success; unless the app is doing something extraordinary, chances that users will […]

swiftui-card-view-listIn this tutorial of our SwiftUI Tip series, we are going to implement a common mobile UI design usually known as Card UI. The SwiftUI framework has made building app UI a breeze. Later, you will see that by using stacks, image, and text views, you should be able to create a card view like the one shown below. Please note that this tutorial requires you to have Xcode 11 running on macOS Catalina (v10.15). Creating a New Project for Building the Card UI If you haven’t opened Xcode, fire it up and create a new project using the Single View […]

Earlier, I gave you an introduction on SwiftUI button, let’s dive a little bit deeper and see how to create a custom button style and animate a button. This is a follow-up tutorial on the beginner’s guide to SwiftUI button, so if you haven’t read that, please check it out first. In a real world app, you may use and apply the same button design on multiple buttons. Let’s say, you’re creating three buttons: Delete, Edit, and Share that all have the same button style like this: You’ll probably write the code like below: As you can see from the […]

loadsharers
by Eric S. Raymond

The internet has a sustainability problem. Many of its critical services depend on the dedication of unpaid volunteers, because they can't be monetized and thus don't have any revenue stream for the maintainers to live on. I'm talking about services like DNS, time synchronization, crypto libraries—software without which the net and the browser you're using couldn't function.

These volunteer maintainers are the Load-Bearing Internet People (LBIP). Underfunding them is a problem, because underfunded critical services tend to have gaps and holes that could have been fixed if there were more full-time attention on them. As our civilization becomes increasingly dependent on this software infrastructure, that attention shortfall could lead to disastrous outages.

I've been worrying about this problem since 2012, when I watched a hacker I know wreck his health while working on a critical infrastructure problem nobody else understood at the time. Billions of dollars in e-commerce hung on getting the particular software problem he had spotted solved, but because it masqueraded as...

git emblem
by Zack Brown

Jonathan Corbet wrote a document for inclusion in the kernel tree, describing best practices for merging and rebasing git-based kernel repositories. As he put it, it represented workflows that were actually in current use, and it was a living document that hopefully would be added to and corrected over time.

The inspiration for the document came from noticing how frequently Linus Torvalds was unhappy with how other people—typically subsystem maintainers—handled their git trees.

It's interesting to note that before Linus wrote the git tool, branching and merging was virtually unheard of in the Open Source world. In CVS, it was a nightmare horror of leechcraft and broken magic. Other tools were not much better. One of the primary motivations behind git—aside from blazing speed—was, in fact, to make branching and merging trivial operations—and so they have become.

One of the offshoots of branching and merging, Jonathan wrote, was rebasing—altering the patch history of a local repository. The benefits of rebasing are fantastic. They can make a repository history cleaner and clearer, which in...

Python
by Reuven M. Lerner

How to get started using Python's asyncio.

Earlier this year, I attended PyCon, the international Python conference. One topic, presented at numerous talks and discussed informally in the hallway, was the state of threading in Python—which is, in a nutshell, neither ideal nor as terrible as some critics would argue.

A related topic that came up repeatedly was that of "asyncio", a relatively new approach to concurrency in Python. Not only were there formal presentations and informal discussions about asyncio, but a number of people also asked me about courses on the subject.

I must admit, I was a bit surprised by all the interest. After all, asyncio isn't a new addition to Python; it's been around for a few years. And, it doesn't solve all of the problems associated with threads. Plus, it can be confusing for many people to get started with it.

And yet, there's no denying that after a number of years when people ignored asyncio, it's starting to gain steam. I'm sure part of the reason is that asyncio has matured and improved over time, thanks in no small part to much dedicated work...

RV
by Kyle Rankin

Having an offsite backup in your RV is great, and after a year of use, I've discovered some ways to make it even better.

Last year I wrote a feature-length article on the data backup system I set up for my RV (see Kyle's "DIY RV Offsite Backup and Media Server" from the June 2018 issue of LJ). If you haven't read that article yet, I recommend checking it out first so you can get details on the system. In summary, I set up a Raspberry Pi media center PC connected to a 12V television in the RV. I connected an 8TB hard drive to that system and synchronized all of my files and media so it acted as a kind of off-site backup. Finally, I set up a script that would attempt to sync over all of those files from my NAS whenever it detected that the RV was on the local network. So here, I provide an update on how that system is working and a few tweaks I've made to it since.

What Works

Overall, the media center has worked well. It's been great to have all of my media with me when I'm on a road trip, and my son appreciates having access to his favorite cartoons. Because the interface is identical to the...

by Zack Brown

David Howells put in quite a bit of work on a script, ./scripts/syscall-manage.pl, to simplify the entire process of changing the system call tables. With this script, it was a simple matter to add, remove, rename or renumber any system call you liked. The script also would resolve git conflicts, in the event that two repositories renumbered the system calls in conflicting ways.

Why did David need to write this patch? Why weren't system calls already fairly easy to manage? When you make a system call, you add it to a master list, and then you add it to the system call "tables", which is where the running kernel looks up which kernel function corresponds to which system call number. Kernel developers need to make sure system calls are represented in all relevant spots in the source tree. Renaming, renumbering and making other changes to system calls involves a lot of fiddly little details. David's script simply would do everything right—end of story no problemo hasta la vista.

Arnd Bergmann remarked, "Ah, fun. You had already threatened to add that script in the past. The implementation of...

DevOps
by Bryan Lunduke

What is DevOps? How does it relate to other ideas and methodologies within software development? Linux Journal Deputy Editor and longtime software developer, Bryan Lunduke isn't entirely sure, so he asks some experts to help him better understand the DevOps phenomenon.

The word DevOps confuses me.

I'm not even sure confuses me quite does justice to the pain I experience—right in the center of my brain—every time the word is uttered.

It's not that I dislike DevOps; it's that I genuinely don't understand what in tarnation it actually is. Let me demonstrate. What follows is the definition of DevOps on Wikipedia as of a few moments ago:

DevOps is a set of software development practices that combine software development (Dev) and information technology operations (Ops) to shorten the systems development life cycle while delivering features, fixes, and updates frequently in close alignment with business objectives.

I'm pretty sure I got three aneurysms just by copying and pasting that sentence, and I still have no clue what DevOps really is. Perhaps I should back up and give a little...

cadnano
by Joey Bernard

This article introduces a tool you can use to work on three-dimensional DNA origami. The package is called cadnano, and it's currently being developed at the Wyss Institute. With this package, you'll be able to construct and manipulate the three-dimensional representations of DNA structures, as well as generate publication-quality graphics of your work.

Because this software is research-based, you won't likely find it in the package repository for your favourite distribution, in which case you'll need to install it from the GitHub repository.

Since cadnano is a Python program, written to use the Qt framework, you'll need to install some packages first. For example, in Debian-based distributions, you'll want to run the following commands:


sudo apt-get install python3 python3-pip

I found that installation was a bit tricky, so I created a virtual Python environment to manage module installations.

Once you're in your activated virtualenv, install the required Python modules with the command:


pip3 install pythreejs termcolor pytz pandas pyqt5 sip

After those dependencies are...

by Adam Verslype

Containerizing the GUI separates your work and play.

Virtualization has always been a rich man's game, and more frugal enthusiasts—unable to afford fancy server-class components—often struggle to keep up. Linux provides free high-quality hypervisors, but when you start to throw real workloads at the host, its resources become saturated quickly. No amount of spare RAM shoved into an old Dell desktop is going to remedy this situation. If a properly decked-out host is out of your reach, you might want to consider containers instead.

Instead of virtualizing an entire computer, containers allow parts of the Linux kernel to be portioned into several pieces. This occurs without the overhead of emulating hardware or running several identical kernels. A full GUI environment, such as GNOME Shell can be launched inside a container, with a little gumption.

You can accomplish this through namespaces, a feature built in to the Linux kernel. An in-depth look at this feature is beyond the scope of this article, but a brief example sheds light on how these features can create containers. Each kind of...

Goodbye
by Kyle Rankin

IMPORTANT NOTICE FROM LINUX JOURNAL, LLC:

On August 7, 2019, Linux Journal shut its doors for good. All staff were laid off and the company is left with no operating funds to continue in any capacity. The website will continue to stay up for the next few weeks, hopefully longer for archival purposes if we can make it happen.

–Linux Journal, LLC

 


Final Letter from the Editor: The Awkward Goodbye

by Kyle Rankin

Have you ever met up with a friend at a restaurant for dinner, then after dinner you both step out to the street and say a proper goodbye, only when you leave, you find out that you both are walking in the same direction? So now, you get to walk together awkwardly until the true point where you part, and then you have another, second goodbye, that's much more awkward.

That's basically this post. 

So, it was almost two years ago that I first said goodbye to Linux Journal and the Linux Journal community in my post "So Long and Thanks for All the Bash". That post was a proper goodbye. For starters, it had a catchy title with a pun. The post itself had all the elements of a proper goodbye: part...

debugging kernel panics
by Petros Koutoupis

A look into what causes kernel panics and some utilities to help gain more information.

Working in a Linux environment, how often have you seen a kernel panic? When it happens, your system is left in a crippled state until you reboot it completely. And, even after you get your system back into a functional state, you're still left with the question: why? You may have no idea what happened or why it happened. Those questions can be answered though, and the following guide will help you root out the cause of some of the conditions that led to the original crash.

Figure 1. A Typical Kernel Panic

Let's start by looking at a set of utilities known as kexec and kdump. kexec allows you to boot into another kernel from an existing (and running) kernel, and kdump is a kexec-based crash-dumping mechanism for Linux.

Installing the Required Packages

First and foremost, your kernel should have the following components statically built in to its image:


CONFIG_RELOCATABLE=y
CONFIG_KEXEC=y
CONFIG_CRASH_DUMP=y
CONFIG_DEBUG_INFO=y
CONFIG_MAGIC_SYSRQ=y
CONFIG_PROC_VMCORE=y

You can find this...

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