Linux User & Developer的No. 186目录

Welcome to the UK and North America’s favourite Linux and FOSS magazine. I’m writing this on the day that it was discovered that anyone can ‘hack’ Apple’s macOS High Sierra by clicking a prompt and typing ‘root’ in the username field. I laughed, but I shouldn’t as it’s quite a ridiculous security failure that should never happen. Back in the world of Linux, we’re looking at ways to reduce the chances of failures of a different kind with our Ultimate Rescue & Repair feature (see p18). We explore what to do when disaster strikes: how to analyse issues, recover from them, and clean and maintain systems to avoid problems in the future. For our second feature, we consider what programming languages we’ll be using in ten years’ time (p60). As…

Top 10 (Average hits per day, month to 17 November 2017) This month Stable releases (5) In development (4) Another Debian-heavy month in the top 10. Meanwhile, several distros are gaining interest for their Windows-like desktop environments… Highlights PCLinuxOS Perhaps the most famous of the Window-likes, PCLinuxOS comes with out-of-the-box support for many graphic and sound cards, and runs most popular hardware.The grey toolbar and menu deliver a strong Windows feel, while a user forum exists for troubleshooting. Zorin OS Based in Ireland,Zorin OS is perhaps the ultimate Windows-esque Linux distro. As well as offering a start menu experience similar to Windows 10,Zorin OS ships with Wine pre-installed. antiX Fast and lightweight, antiX uses a classic Windows-style desktop taskbar and start menu reminiscent of Windows XP. Based on Debian, antiX…

“The Vivaldi browser started life in 2015 as both a response to a change of direction at Opera and what Jon Stephenson von Tetzchner, the CEO and past co-founder of Opera, sees as a demand for a web browser that caters for internet power users. Von Tetzchner believes that the main browsers are over-simplifying their experience: “They are basically adapting to someone that doesn’t exist,” says Jon talking from Magnolia Innovation House outside Boston. “Any feature that’s used by not so many people gets removed and the software gets dumber and dumber in a way.” Vivaldi is essentially walking in the opposite direction with signature features such as tab grouping, a built-in screenshot capture tool and the ability to take notes right in the browser that are heaped together with…

Linus Torvalds announced the release of Linux kernel 4.15-rc1, following the “usual two weeks of merge window” (the period of time during which disruptive changes are allowed into the kernel tree). In his mail, Linus notes that this is “about the only thing usual about this merge window”. Due to the US Thanksgiving holiday, many developers (including Linus) were on vacation at the back end, and while Linus had warned everyone to front-load their patch pull requests, he did have to get much more strict about what he was willing to take at the last minute. Overall, he was fairly happy about the process, and in particular “really liked” enforcing that patches had to have flowed through Stephen Rothwell’s linux-next tree before going to Linus. This development cycle is expected…

“There is always the risk of any attempt to repair file system damage actually making things worse” If anything is wrong with a disk drive or file system, the easiest way to make it worse is to write to it. So the first step is to boot from a rescue CD so you can mount the drive read-only. Before mounting it, you should make a backup image of the drive. The usual tool for this is dd, but that program will exit with an error as soon as it encounters any issue reading from the drive, so we use ddrescue instead. This does the same job as dd but will try again if it hits an error and if it cannot read part of the drive, even after multiple tries,…

1 Rebuild GPT partition table The GPT standard stores backup copies of the partition table on the disk. Using gdisk, press R to enter the recovery menu and C to load the backup table. To rebuild the main partition table from the backup, press B, then W to save. 2 DOS partition table The old-style DOS partition table is less friendly, with only one copy. So before things go wrong, use fdisk to dump the partition data to a file, just in case things go wrong. If you don’t have a backup, you’ll need to try testdisk. 3 Scan for partitions You can use testdisk to scan the entire disk for the tell-tale signs of partitions. Run testdisk from a root terminal to see a list of available drives. You…

In the first part of this series, we learned about the UNIX philosophy that underpins all the commands we have been learning about. Part of that philosophy was the insistence that all programs should communicate with one another through a text stream, since that is a universal interface. This is a powerful idea: as long as two programs function by taking in textual input and printing out textual output, then they can interact together through a pipeline, even if they haven’t been explicitly designed to work together. The main pitfall behind this idea is that the textual output from one program might not be in the format that the second program expects as input. In the last issue, we met one of the tools that can be used to get…

“The MQTT module for the C++ framework is not complete as of v5.10– we must make do with a beta version from GitHub” Event-oriented architectures are ideally suited to many tasks. For example, take a system that forwards humidity sensor data to various clients. The biggest benefit is that the arrangement between producers and consumers can be organised on the fly: if readings must also be forwarded to a logger, no changes in the creator (the sensor) or the other consumers are required. Furthermore, testing event-driven architectures is greatly simplified compared to traditional systems. This phenomenon is explicable if you look at the way in which parts are tied together – replacing the aforementioned humidity sensor with a mock-up class is really simple: you implement the event-sourcing protocol and proceed…

Temperatures are beginning to drop to freezing and the days are already short. For those worried about spending all their money on running the boiler, January is often the most agitating month. You’ve already bled your radiators and are resigned to wearing jumpers, but are still concerned about the pipes freezing and bursting. In this issue of LU&D, we’ll be creating an Arduino temperature monitor which can be placed anywhere in the house and run for months on end, automatically reporting its data back to base so that you can make informed decisions about when to turn the heating on. We’ll begin by taking a lower-power Arduino and preparing the temperature sensor. In LU&D183 we used an LM35, so in this tutorial we’ll show you how to interface with the…

“We use the robots for fun programming exercises” Can you give us an overview of the micro robots projects? What’s the idea behind your micro robots? The micro robots project was formed when discussing how the Imperial Robotics Society could develop a course for teaching higher-level multi-robot behaviour. We have a very successful course introducing the basics of robotics on a small robot platform, roughly the size of an A5 sheet of paper, but robots of this size quickly become a problem if you want to control a load of them at once. The area you have to cordon off becomes prohibitive; also, generally you can only have one set that the class must share. We decided that this course would not need access to the low-level hardware, as that…

"All of the SQLite code is part of your code" In previous issues, we have looked at how to use data that is stored in files using regular file I/O. From here, we moved on to looking at how to use pandas to work with more structured data, especially in scientific work. But, what do you do when you have data that needs that go beyond these tools, especially in non-scientific domains? This is where you likely need to start looking at using a database to manage information in a better way. This month, we will start by looking at some of the lighter options available to work with simple databases. In terms of lightweight databases, SQLite is the de facto standard in most environments. It comes as a C…

RAM 2GB Storage 20GB Specs CPU: 64-bit Intel or AMD processor Graphics: AMD or Nvidia hardware Available from: https://system76.com/pop System76 is one of the few retailers to sell computers with 100 per cent Linux compatible hardware pre-loaded with Ubuntu. The desktop may not be Canonical’s core business, but it is at System76—the end of the Unity project affected 91 per cent of its business. In response, it put together a distribution of its own to offer customers a user experience in line with the company’s hardware. The company went distro hopping and settled on the latest Ubuntu with GNOME Shell as the base for its custom distro christened Pop!_OS. Instead of focusing its efforts on mainstream desktop users, System76 is designing a distro geared towards creators, developers and makers: “If…

The Lightweight Qt Desktop Environment—called LXQt for short—will draw a graphical user interface without consuming too many resources. The desktop environment is a mix of GTK-based lightweight desktop, LXDE, and Razor-Qt, which was an equally lightweight—but less mature—desktop that used the Qt toolkit. The recent releases of the mainstream desktop environments such as Gnome and KDE have put them out of the reach of low-spec machines, which is why many popular distros have a LXQt-based flavour in their arsenal of releases. LXQt is also popular with users of newer more powerful machines, as it helps free the resources for more CPU-intensive tasks such as video processing. The latest version of the desktop includes better support for HiDPI displays. The new release ships with a new Open/Save File dialog, and includes…

1 Mozilla Firefox Quantum Released amid a storm of publicity, Firefox 57 (known as Quantum) has proven popular. The biggest update in Firefox’s history, Quantum is faster than Google Chrome, and uses 30 per cent less memory. These changes may secure Firefox’s future, but are they enough to challenge Chrome? 2 Midori Employing the WebKit rendering engine, Midori is associated with the Xfce desktop and developed to the same principle (“making the most of available resources”). With a low footprint, it can be found on many light Linux distros. 3 Chromium Anyone who has used Google Chrome should be comfortable with its open source sibling. Much of the same functionality is there, along with support for extensions. Chromium is fast and easy to use. 4 Brave Based on Chromium and…

What’s impressive about Vivaldi is the features that are being released with each update. For instance, the last release, 1.13, focused on the Window Panel. This is a classic example of Vivaldi catering for power users who tend to have lots of tabs open. The panel presents a ‘tree-style view of tabs to the side of the browser window for easy management. You can do such things as grab and drag tabs; group them by topic; use Tile Tab Stack feature to compare pages side by side, mute individual tabs or hibernate tabs for better performance: “It’s another way to do tabs,” says von Tetzchner, ”and we just know that people have very different opinions and strong opinions how they should do their tabs.” The Vivaldi team has worked on…

1 Choose a method Boot from the Clonezilla live CD and choose a cloning method. Here we are sending to an image file, but you can also clone to another disk, as long as it is at least as large as the source drive. Other options allow for a network backup to or from a Clonezilla server running on another computer. 2 Storage locations When backing up to an image file, it does not have to be on the same computer. Backing up to a second local drive is fastest, but you can also use a number of network protocols. SSH is the simplest when it can be used, but you can even backup to a web server using WebDAV. 3 Beginner or Expert? Choose your level of expertise. Beginner…

Are you an ‘accidental admin’? Someone who realised, too late, that they were responsible for the workings of a Linux server and – because something has gone wrong – finds themselves lost in a world of terminals and command lines? What is SSH?, you may be asking yourself. Do those letters after ‘tar’ actually mean anything real? How do I apply security patches to my server? Don’t worry, you’re not alone. And to help you out, we’ve put together this quick guide with essential Linux commands that every accidental admin should know. Becoming an accidental admin While we’d argue that they should, not everyone who starts using Linux as an operating system does so through choice. We suspect that most people’s first interaction with Linux happens somewhat unwittingly. You click…

Proxies are great tools for pen-testing web applications. They are capable of detecting common vulnerabilities on websites (SQL-i, XSS, sensitive data exposure, and so on), while providing you with a powerful framework for circumventing website client-controls, performing manually scans or conducting automated attacks. A lot has been written about using either Burp or ZAP! proxies during a web pen-testing engagement. But it is not all about the web – think about all those embedded and IoT devices making use of the HTTP protocol behind the scenes in order to send or receive data, communicate with some server in the cloud, or just perform some other unattended tasks. Not to mention smartphones running either Android or iOS! Most of the apps you are using on a day-to-day basis employ the HTTP…

This month’s Java tutorial has a slightly different focus from previous issues. Rather than make any substantive modifications to the functionality of our code, we will be rewiring our existing code in order to fit it into a Java software framework called Spring. Unlike traditional programming, where we take responsibility for creating an entire program, when we work with a software framework, our focus is on providing components for the framework and configuring it to use them. The way we have set up our program, with important classes backed by interfaces, makes it well suited to this style of programming. We will be using the Spring Framework, which is probably the most popular framework for Java. Using Spring will allow us to incorporate an important design pattern – dependency injection…

1842 Ada Lovelace writes the first computer program, designed to run on Charles Babbage’s unfinished Analytical Engine 1948 The ‘Small-Scale Experimental Machine’ becomes the world’s first stored program computer, programmed in machine code 1949 EDSAC is programmed in one of the first assembly languages, Initial Orders. The assembler was hard-wired into it 1952 Autocode is the first high-level language. It’s the ancestor of all today’s languages, even though it never took the world by storm 1957 Fortran is the first mainstream, high-level language, ideal for scientific application – the main use of early computers 1958 LISP uses the paradigm of list processing and gains support for AI, it's different in nature from other early high-level languages 1958 ALGOL, the first block-structure language, is designed and encourages improved programming techniques. 1959…

Martin Lester is a researcher at the University of Oxford with an interest in the theory and application of programming languages. Today’s top languages are mostly general purpose, imperative and object-oriented, so does that paradigm represent the pinnacle of development? Just because a language is popular and widely used, it doesn’t necessarily mean that it’s been chosen for a good reason, or indeed chosen at all. If a developer contributes to an existing project, the language is already fixed. Most professional developers work on existing projects, so get no choice in what language they use. So are you saying there is more to come? C++, Java and Python have all undergone a lot of changes in the last ten years or so. Whenever a new feature is added to a…

This issue we’re looping back to where we started with the Python coding in Minecraft series in LU&D178. We’ll be using Python code to draw shapes directly in our Minecraft worlds. This tutorial is written with Minecraft Pi Edition in mind, but you don’t have to be running Minecraft on a Raspberry Pi to follow along. We’ve put together a package that will work on any version of Minecraft, so you can run this tutorial on your favourite flavour of desktop Linux, Pi or no Pi. To allow Python to hook into Minecraft, you’ll need to install McPiFoMo (see Resources) by extracting the contents of the .minecraft directory into ~/home/.minecraft. McPiFoMo includes MCPiPy from MCPiPy.com and Raspberry Jam, developed by Alexander Pruss. Provided you have Python installed, no additional software…

Sometimes, even SQLite may not be lightweight enough, depending on your specific requirements. In these cases, you do have another option. There is a very old file-backed database from the earliest days of UNIX, called dbm. Dbm databases store data as a set of key-value pairs within a file on the file system. To start, you will need to open a database with code like that given below. This opens the database in the file example.db, or creates it if it doesn’t already exist. You can insert a value to a given key, or get a value based on a key. Below is an example of storing a name/phone number pair. When you do the query, you need to remember that everything is stored as byte strings, so you will…

Linux has no dearth of advanced text editors that moonlight as lightweight IDEs as well and we ran a group test of some of the best a few issues ago (LU&D182, Pg 81). CudaText is one such cross-platform editor that’s primarily designed to write code, but can double up as an advanced text editor. The editor has all the usual coding conveniences, like syntax highlight for several programming languages, including C, C++, Java, JavaScript, HTML, CSS, Python, and more. You also get code completion for some languages like HTML and CSS, code folding, the ability to search and replace with regex, as well multi-caret editing and multi-selection. You can extend the functionality by installing additional plugins that are written in Python. The project releases precompiled binaries for Debian-based distros. On…

If you’ve worked with images, either professional or sorting through vacation clicks, you know a lot of image processing work is monotonous—repeatedly converting, resizing and rotating images to make them suitable for print or passing around. Although you can use virtually any image viewing or editing app, from DigiKam to GIMP, for this task, you’ll save yourself hassle by employing a dedicated batch conversion tool like Converseen. Converseen is a straightforward frontend to the command-line conversion utilities in ImageMagick. You can use the app to convert images to and from over 100 formats, rotate and flip them, change their dimensions and rename them in a fraction of the time it would take to perform these tasks manually. You’ll find installable binaries for Ubuntu, Fedora and OpenSUSE on the project’s website,…

ABOUT Eating Robots Taken from the new book Eating Robots by Stephen Oram: near-future science-fiction exploring the collision of utopian dreams and twisted realities as humanity and technology become ever more intertwined. Sometimes funny and often unsettling, these 30 sci-fi shorts will stay with you long after you’ve turned the final page. http://stephenoram.net He stood naked in front of the full-length mirror, flexing his biceps. The mirror flashed an amber warning, reminding him to stand still while it scanned his organs, blood, bones and skin. It would evaluate his health and adjust the multitude of enhancement implants scattered throughout his body, fine-tuning them as it went to maximise his physical and mental performance. This daily routine made him feel trapped and cornered, as if the mirror was a docking bay…

Could the Pentagon be abandoning proprietary software foro open source? That’s the implication of a key portion of the National Defense Authorization Act for Fiscal Year 2018, in an amendment introduced by Sen. Mike Rounds and cosponsored by Sen. Elizabeth Warren. But why? First, as the world’s biggest single employer, the Department of Defence has a massive IT requirement. A lot of money is spent on data warehousing, statistics, briefings, presentations, spreadsheets and documents. Licencing costs are expensive. Second, there is a perception that waiting for closed-source applications to update puts the DoD at a disadvantage. Rather than playing catch-up, it’s preferable to adopt new software tools. Procurement takes time, both in terms of signing off requests and waiting for a release date. Then there’s the roll-out, another potential delay.…

You can’t cover Vivaldi without addressing the elephant in the room, and that’s the browser’s current lack of a full free or open source licence. It is a complicated situation, as all the changes made to the Chromium engine source code (available at https://vivaldi.com/source) are released under a BSD licence. This type of licensing doesn’t require source code to be distributed, although Vivaldi does, and also makes the UI code accessible to read in plain text. “Every change we do to the C++ code—that’s open,” says von Tetzchner. “When it comes to the HTML side, we haven’t decided on a licence. We have had discussions—should we put it out with a licence? But we’ve not really done that.” And people are able to go in and change the code as…

“The systemd journal is basically a system log but with an index, making finding info much easier8 So what can we do to identify the problem without making it worse? The main thing to remember is ‘don’t guess’. Look at what happens when you experience the problem without trying to jump to the first possible cause that pops into your head. Does the computer boot? If not, at what stage does it stop and what messages do you see? Do you see a GRUB menu? Does selecting any option boot the computer? If the answer to any of these is ‘no’, reach for your copy of Rescatux which has various options to quickly fix GRUB issues. Does Linux start to boot but never reach the desktop? Do you get as…

Disk drive failures are a common cause of grief and can fall into a number of categories. Terminal drive failure is the worst and you can usually say goodbye to your data, unless it is valuable enough to justify the services of a specialist recovery company, but anything that valuable would be backed up, right? Next is a corrupted partition table, where the drive is visible but none of its partitions can be seen. Before you start trying to fix the drive on these cases, may sure it is at fault. Try a different cable, plug it into a different port, or even computer, to be sure that it is not something as simple as a loose or damaged cable, or a problem with your computer’s disk controller hardware. Naturally,…

Once everything is working well after you have repaired it, or preferably before you have needed to, there are things you can do to keep your system in good health, or at least be better prepared for problems. The first, and most important, is to set up a backup system, and make it an automated one. Don’t rely on your remembering to do it, but do test the backups from time to time. While you are automating the backups, set up smartd to run in the background and have cron run Rootkit Hunter. Once those are set up, you can forget about them: they will let you know if they want your attention. To keep an eye on your temperatures: a desktop system monitor like Conky or GKrellM can help…

The old-school approach to recording a walkthrough used to involve pointing a camera at your screen – and you still see those on YouTube, especially if someone is covering BIOS/EFI guidance. While this works in theory, it is grossly inefficient: keep in mind that your computer generates digital picture information, which is then output onto an analogue medium. An analogue camcorder then re-digitises this information, only to store it into a video file. In addition to the effort involved in getting the alignment right, digitisation and quantisation noise never sleep. Capturing programs used to be difficult because of the high processing power required for encoding live videos coming from a framebuffer. Fortunately, the development of ever-faster processors ameliorated this problem. For instance, your author often records live video of Android…

1 OWASP Zap! Proxy The Zed Attack Proxy (ZAP) from OWASP is an incredible and powerful open source proxy quite similar in functionality to Burp. It ships with a lot of automated tools to scan for vulnerabilities in web applications and it can be automated thanks to its powerful REST API. http://bit.ly/OWASP-ZAP 2 mitmproxy This is an open source MITM proxy that allows HTTP and HTTPS interception with an ncurseslike graphical interface. If you are a fan of tcpdump, try mitmdump instead. You can install it right away on your Debian-based distro: apt-get install mitmproxy. https://mitmproxy.org 3 TamperData An outdated Firefox add-on, but still functional. It is as simple as it gets: it can intercept and manipulate POST parameters. It is quite unstable, but perfect for quick-and-dirty tests on-the-fly. http://bit.ly/TamperData…

Colin Runciman works at the Department of Computer Science at University of York with research interests in programming languages and systems, functional programming and software tools. Given that many of today’s languages date back many years and their roots go back 50 or 60 years, have high-level languages reached maturity or are there further developments to come? Further developments should be expected in at least two areas. First, stronger type systems will increase static guarantees that certain kinds of failure cannot occur when the program runs, and that many desired correctness properties are verified. Second, more powerful methods will be developed to compile programs effectively for execution on multi-and many-core machines, including strategies for portable optimisation. The terms fourth and fifth generation date back quite some time but such languages…

Google Assistant is a virtual personal assistant, designed to make your life easier by scheduling meetings, running searches and even displaying data. In April this year Google released an SDK (software development kit), allowing developers to build their own Assistant-related hardware. In this guide you’ll learn how to integrate Google Assistant with your Pi and run a demo which can respond to your voice commands. As the Pi doesn’t have a built in microphone, we’ve used the ReSpeaker 2-Mics Pi HAT, which is designed specifically for AI and voice applications. The ReSpeaker HAT costs just £12 and is compatible with the Pi Zero as well as the Pi 2B and 3B. However, if you have a USB microphone, you can use this instead. By default, Google Assistant only responds to…

Price From £195 for 500GB (reviewed £489, 5TB) Website  https://istorage-uk.com Specs Capacity: 500GB-5TB Data transfer speed: Up to 148MBps (Read),140MBps (Write) Power supply: USB bus-powered Interface: USB 3.1—up to 5Gbps Hardware data encryption: Real-Time Military Grade AES-XTS 256-bit Full-Disk Hardware Encryption Warranty: 2 years Dimensions (W, D, H): 124mmx84mmx20 mm (500GB,1/2TB), 124mmx84mmx28mm (3/4/5TB) Weight: 500GB/1/2TB 225g, 3/4/5TB 331g For those who carry sensitive information around with them on a daily basis, there’s an ever-present concern with losing the device carrying that precious data (or worse, having it stolen). This is concern addressed by the new iStorage diskAshur Pro2 external HD, a compact storage device designed to work with secure data without the need to install software on all the systems it will meet. The Pro2 retails at £489 ($651), comes…

Linus Torvalds likes to track whatever he does. He wrote Git to keep track of the kernel development and Subsurface to log his dives. Torvalds likes to don the wetsuit and plunge underwater whenever he isn’t busy hacking away at the Linux kernel. He couldn’t find a good app to log his dives, so naturally he wrote one himself. Simply put, Subsurface helps keep track of scuba dives. You can use it to import data from one of the supported dive computers, usually via USB. Once your data is imported, you can view and edit dive details from the intuitive user interface. The app also enables you to log dives manually. The app shows a dive profile graph that plots dives as a line graph. It shows ascent and descent…

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