Linux FormatAugust 2021的目錄

Jonni Bidwell Speaking from experience, it’s a good idea to change your bash prompt or use tmux decorations – anything to embellish the fact that the machine you’re working on is remote. It’s no fun when you think you’re dd-ing a USB stick, but it’s actually your server’s hard drive. Les Pounder A few years ago, the 4TB drive in my server died and it took the best part of a weekend to rescue all the data from a rapidly failing drive. My advice is to have backups of your important data – a second drive and a cloud service is the ideal solution. Michael Reed If you have the room, consider separating your home directory, your root (installation) directory and your data directory. You can do this by making…

“IT projects are notorious for running over time and over budget (see, for example, just about any government IT project). This also applies to many IT projects taking place at SMEs (small and medium-sized enterprises) too, but it doesn’t have to be this way. Here’s a suggestion for your next IT project, even if its aims and aspirations are a little more modest than introducing identity cards for the UK’s population. Before you start, write a checklist that you can refer back to at the end of the project to ensure that the project has met its goals. You may be surprised at how hard that is to do. Next, you then need everyone involved with the project to agree that the list is a full and complete one (again,…

The Document Foundation (TDF) has published its annual report for 2020 (which you can read at http://bit.ly/LXF278TDF2020), and as you’d hope, the entire report was made using its LibreOffice suite. While 2020 was supposed to be a memorable year, with the 10th anniversary of LibreOffice being marked with events around the world, unfortunately, the year was instead memorable for something much different: the global Covid-19 pandemic. This meant those celebrations were cancelled, but the year was still a busy one. There were elections for the foundation’s membership committee, and events to mark International Translation Day (LibreOffice is available in 119 languages thanks to the work of its community). The TDF also had a record year on the financial front. With many businesses and individuals having to work from home, downloads…

Linus Torvalds closed the merge window for kernel 5.13, and released a series of Release Candidate kernels that have since settled down and stabilised ahead of the final release. Linus noted that there were “1,800+ developers and 14k+ non-merge [non-administrative] commits”, which is on the larger side as Linux development cycles go. Still, it’s been a fairly calm cycle so far without the usual kinds of scurrying that can happen by the time rc3 comes around. As we reported last month, 5.13 gains initial support for Apple M1 bare metal hardware. In addition, it also includes a new option to randomise the location of the kernel stack on every system call, and the removal of the legacy /dev/kmem special file that traditionally allowed (privileged) applications to poke directly into kernel…

Many programs, especially background daemons, can get very chatty, sending all sorts of details about what they’re doing to log files. This can either be the system log or individual log files, generally stored in /var/log. As the weeks and months go by, this can build up to a substantial amount of data, and disk space consumed. If you use systemd’s journal as the system log, it takes care of this by compressing or discarding old data to keep disk usage within limits. By default, this is to use no more than 10 per cent of the filesystem’s space and to always leave at least 15 per cent of that space free. You can adjust these settings in /etc/systemd/journald.conf. For other log files we have logrotate. Log files are text…

More maps Thank you for the article on OpenStreetMaps. I’ve been a contributor since I bought a GPSR in 2009. I do think there are a couple of related programs that deserve a mention. If you have a Garmin GPSR, you can produce your own maps using freely downloaded data and the mkgmap utility. With a little tuning, you can change the way roads, areas and points are rendered to suit your preferences. The maps produced are up to date, more detailed and don’t include the copyright monitoring “artefacts” found in commercial mapsets. And there’s an OSM-based mapping application – OsmAnd – which operates from an offline internal map database, so there’s none of the “phone home to the mothership” constant reporting of your location, as involved when using Google…

Virtualisation is a complex process, so you would expect extensive documentation to come with each of these programs. However, that’s not always the case. The documentation for Virt-manager consists of a man page listing the startup options and a four-question FAQ on the website. About the only real help you get are bubbles that appear over various GUI options. VirtualBox goes the other way, with a 400-page PDF manual, which seems scarily huge for first-time users, but does have an easy primer on creating your first virtual machine. This really is commercial-level documentation, and not a man page in sight! Aqemu takes a similar approach to Virt-manager, but without the helpful bubbles. This is a previously abandoned project that has been resurrected, but it would be nice if someone could…

The winter of 2020 will be remembered by many as ‘not a particularly festive time’, but spare a thought for CentOS (the community-powered distro based on Red Hat Enterprise Linux), who were told unequivocally in December that further development would be axed. Contrast this with the headlines of rose-tinted 2014, when CentOS announced that it would be partnering with Red Hat, giving the company access to vast resources while still enabling it to remain an independent, community-driven project. Red Hat recognised the value in CentOS, which at the time of the union was the world’s most popular server distribution (Debian later reclaimed that prestigious title). A lot can happen in a few years (Red Hat being bought by IBM, for example). Issues of governance, development and other foibles led to…

The Raspberry Pi Pico went on sale at the start of the year and is powered by the RP2040 SoC. Furthermore, the RP2040 surface mount device (SMD) integrated circuit (IC – the chip itself) has been available to select industry patterns. Hence Pimoroni, Adafruit et al being able to develop spin-off RP2040-packing products. It turns out that because of unprecedented demand the programme to provide the RP2040 IC package was accelerated by three months to the beginning of June 2021. This resulted in 40,000 units being pulled out of general circulation and offered to makers and other businesses at the price of $1. Eben Upton of the Raspberry Pi Foundation explains, “This will give people time to develop their projects and products, while we clear out the rest of the…

Some components have stranded wire leads because these are flexible, but they don’t easily plug into a breadboard. Sometimes the manufacturer tins the end of the leads with solder. If not, the easiest solution is to extend each of the device’s leads with a proper patch lead, using a small piece of terminal strip. When you buy a set of patch leads, you’ll probably be supplied with a variety of colours. Using specific colours for particular purposes will help you to spot mistakes if your circuit doesn’t work. For example, you could use black or blue leads for -ve and red leads for +ve. We don’t recommend it, but complicated circuits have been patched together on breadboards. You might be interested to learn, for example, that there are reports of…

You can connect a mouse or touchpad to the Pi. Touchpad use is almost exactly the same as in Windows. Tapping with two fingers gets you the right-click menu, and scrolling involves dragging two fingers down the pad. If you want to reverse this, there’s an option in Settings>Mouse, from where you can also adjust the pointer speed. Pressing the Windows key brings up the Launcher, from where you can choose between recent applications or search for a new one, and there’s a circle button in the bottom-left corner that does the same thing. Settings>Keyboard contains a great many options for mapping a Windows keyboard to the Chromebook standard, enabling you to change the behaviour of Ctrl, Alt, Esc, Backspace and more. Finally, Google Assistant can be activated, but is…

Testdisk and Photorec have long been part of almost all data recovery CDs and toolkits because of their effectiveness. But they aren’t the only tools that can help you recover deleted files, or extract useful data out of formatted or corrupted disks or partitions. Although it hasn’t seen a new update in some time, Extundelete is quite useful in recovering files, especially from ext3 and ext4 partitions. It works best when you already know the exact path of the file you wish to recover, such as with the sudo extundelete /dev/sda7 -restore-file ~/Documets/todo.txt command. You can alternatively use the sudo extundelete /dev/sda7 -restore-all command to recover all files from the specified partition. Scalpel is another file carver, just like PhotoRec, and so can work independent of the underlying filesystem. This…

If you’re taking a photograph to use as a reference image then there are a few useful guidelines we can give. Aesthetics aren’t important, and we want something clear, with as little perspective distortion as possible. As ever with photography, as much light as possible will produce the clearest shots. If you’re using a camera, step away from the subject, physically, and zoom in (50mm equivalent or more) to compress perspective. If you’re using your phone’s camera, step back and then crop the image afterwards. If you get too close, with the wide angle lens of a phone camera then you’ll exaggerate the effect of perspective, and for our uses we want to flatten things as much as possible. For the same reason, make sure that the camera or phone…

The 8080 was only Intel’s third ever microprocessor, following on from the four-bit 4004 which appeared in 1971, and its first eight-bit chip, the 8008 which appeared soon after. Its instruction set comprised just 78 instructions, and our simple machine code programming example served to illustrate one of its shortcomings. In particular, the five instructions needed to add two values from memory and write the answer to another location is a couple more than many people would expect, if they’ve not previously used the 8080. Specifically, on processors that came out just a couple of years later, just three instruction would have been needed. First, load a value from memory into the accumulator; second, add a value from memory to the value in the accumulator; and third, write the value…

If you want to access the target system as root without a password, uncomment the EXTRA_IMAGE_FEATURES ?= “debug-tweaks" line in the local.conf file. If you don’t do that and at the same time deflect from explicitly adding a user in one of your recipes ( EXTRA_USERS_ PARAMS ), you won’t be able to log in the target system at all. Use the following command to quickly find out if you have enabled root access without a password or not: This is deliberately maintained as a part of Poky’s security policy. As you may know, one of the most common vulnerabilities of routers, Pi devices and other boards that Poky is designed to counter is a weak or missing root password. The current approach to network security assumes that once you…

A message broker such as RabbitMQ acts as a middleman for software to exchange information using one or more queues for storing the messages. Usually, we don’t interact directly with RabbitMQ. A client sends data to RabbitMQ, which in RabbitMQ terminology is called a producer, and another program reads these messages, which in RabbitMQ terminology is called a Consumer. So, a producer is any application that sends messages whereas a consumer is any application that receives messages from the queue. A queue is a FIFO (first in, first out) structure that supports two operations: adding elements and getting elements. The AMQP protocol, which stands for advanced message queuing protocol, is a open protocol for message-oriented middleware. The characteristic features of AMQP are message orientation, queuing, routing, reliability and security. AMQP…

It’s a common misconception that concurrency is the same thing as parallelism. Parallelism is the simultaneous execution of multiple entities of some kind, whereas concurrency is a way of structuring your components so that they can be executed independently. It’s only when you build software components concurrently that you can safely execute them in parallel, when and if your operating system and your hardware permit it. The Erlang programming language (www.erlang.org) did this a long time ago – long before CPUs had multiple cores and computers had lots of RAM. In a valid concurrent design, adding concurrent entities makes the whole system run faster because more things can be executed in parallel. So, the desired parallelism comes from a better concurrent expression and implementation of the problem. The developer is…

USING THE LXFDVD Using Linux for the first time can be very confusing. It’ll most likely be unlike anything that you’ve operated before, especially if you’re used to Microsoft Windows or Apple macOS. Generally our DVDs are designed to be run directly, which is to say that when you first power on your PC (or Mac, see below) it should ‘boot’ from the DVD – so before Windows or macOS even starts to load – with Linux running directly from the DVD. This trick is known as a Live Disc. It enables you to try out the various versions of Linux without having to install or change anything on your PC. Just remove the DVD, restart your PC and it’ll be exactly as you left it. While many systems will…

I suspect that many readers, whenever Linux is mentioned, imagine their personal computer sat in their homes. That’s great: it shows how far the GNU/Linux world has come. It’s clearly functional enough, easy enough and widespread enough to be used as a desktop system by your normal home user. This does mean that much of our focus these days is on desktop systems – even if some of this is development or home-server applications. Perhaps we forget that most systems running Linux are servers, be that real or virtual. So with Red Hat pulling the server rug from under the CentOS community, we’re taking the chance to look at how you can put together “better” servers using one of the most stable, reputable and well-regarded code-bases, whether that’s with CentOS…

The audio-editing program Audacity is one of the most popular open-source software in the world. However, recent developments have threatened to tarnish Audacity’s reputation. In April, Audacity was acquired by Muse Group, which is made up of a number of music brands, including Ultimate Guitar and MuseScore (read about the acquisition at http://bit.ly/LXF278MuseGroup). This worried long-term users, even though Muse Group promised that “the software will remain forever free and open source.” While this may have allayed some people’s fears, things took another concerning turn when a pull request appeared on GitHub (http://bit.ly/LXF278AudacityGit) for “Basic telemetry.” While the pull request was updated to ensure that “Telemetry is strictly optional and disabled by default. No data is shared unless you choose to opt-in and enable telemetry,” the idea that collecting user…

“With the summer months upon us, so too is the usual conference season, except these are still far from usual times. Several of the big annual Linux conferences have said they’ll have to go virtual once again. As Ted Ts’o put it, it just wouldn’t be practical to hold the kind of discussion format in a socially distanced and safe manner. And while a growing number of countries are rolling out vaccination programmes, others are experiencing a far worse time, to say nothing of international travel constraints. Given the situation, it seems only reasonable to exercise caution, but the conversation on the Linux Kernel Mailing List (LKML) quickly became one of the more bizarre I’ve seen. An IT consultant from Germany replied with a rambling, incoherent rant, laced with conspiracy…

We’d love to try and answer any questions you send to lxf.answers@futurenet.com, no matter what the level. We’ve all been stuck before, so don’t be shy. However, we’re only human (although many suspect Jonni is a robot), so it’s important that you include as much information as you can. If something works on one distro but not another, then tell us. If you get an error message, please tell us the exact message and precisely what you did to invoke it. If you have, or suspect, a hardware problem, let us know about the hardware. Consider installing hardinfo or lshw. These programs list the hardware on your machine, so send us their output. If you’re unwilling, or unable, to install these, run the following commands in a root terminal and…

Virtualisation is a big thing these days. It’s used by big data companies to spin up extra resources when needed, because it’s much quicker to boot a VM on a running OS than to boot a hardware box from scratch. However, we’re looking at the other side of virtualisation here: running virtual machines on your desktop. This may be because you need to use a different distro from time to time – either to see if the grass on the other ISO really is greener or because you’re testing software on multiple distros. It could be that you have to use a certain piece of Windows software that won’t run in WINE, but you can’t or don’t want to reboot. It could be that you need to keep some software…

Not all of these VM options are completely open source and that can affect compatibility with your system, both in a philosophical way and at a more pragmatic level. Aqemu, Virt-manager and Gnome Boxes are all based on Qemu and are completely open source. Their hardware interface is through modules included in the standard Linux kernel and should work on just about all distros. The only time you may run into problems is if the KVM hardware acceleration isn’t enabled on your computer, which is turned on and off in the BIOS settings menu. VMware Workstation Player is completely closed source, meaning it can only work with the distros it supports. It also requires kernel modules to be compiled when it’s first run, and after any kernel updates, which means…

One of the things that makes X unique is its network transparency. This is about more than running programs remotely with ssh -X , although that’s a convenient side-effect. An X application has no awareness of whether it’s running locally or remotely. This was a decision that made sense at the time, given the relative youth of desktop computing, but it adds an unnecessary layer of complication to today’s workloads. And that’s why there’s no network transparency in Wayland, as Collabora’s Daniel Stone explains. “It’s deliberate, although Xedit or Motif applications work over the network in Wayland as well as they ever did. That’s because it’s using the server’s core rendering and accelerated rectangles and what have you. But since GTK2 I think all that happens is that pre-rendered buffers…

The best part of my roller-coaster journey with Raspberry Pi has been, and continues to be, the fantastic community that has grown up around it. It resonates loudly with my experience as a young college student. Graham Beech, a laboratory technician, introduced me to computers in the form of a PDP8. His belief, help and encouragement changed my life for the better. The Raspberry Pi mission has galvanised makers, teachers, professional engineers, enthusiasts and folks taking their first steps in “digital making” to all come together and help each other move forward and create something truly wonderful. I’ve been hugely fortunate to meet so many of the Pi community at the hundreds of events I’ve attended over the years. From São Paulo to Stockholm, I’ve been in awe of your…

Living through a pandemic has greatly increased the price of webcams. As more and more of us work from home, speak to loved ones using video chats, or record cute cat videos for YouTube, demand for good-quality webcams has pushed prices of even basic cameras. However, for this game you don’t need the latest and greatest camera. We used a 10-year old Microsoft 720P camera and it worked with no driver installation. The official Raspberry Pi camera can’t be used in this project because it doesn’t have a microphone, which is necessary to detect sound and start the game. If you have a cheap webcam lying around, you can use it with a Raspberry Pi and a quick way to test if it works is to use guvcview, a great…

If your Raspberry Pi setup is unusual, perhaps due to the hardware you’ve connected to the device, but you don’t feel the need to regularly back up, there is an alternative. Instead of backing up the full SD card, or even archiving the /home directory, why not simply make a copy of config.txt? Existing in place of a system BIOS, config.txt stores various system parameters required for the correct running of the Raspberry Pi. Every Raspberry Pi operating system features a config.txt file, which is read by the system’s GPU as the device boots. While the Raspberry Pi is running, config.txt can only be edited as root. You’ll find it in the /boot directory as /boot/config.txt. With the microSD card inserted in other systems, config.txt can be edited using a…

Changing desktop wallpapers in Chromium OS gets its own tool, accessible from Settings>Personalization. It’s filled with desktop backgrounds, and a few have the option to refresh daily. There are some beautiful options available, but sadly they don’t appear in the Files tool. Right-clicking the desktop brings up a menu, with only three options: to show or hide the dock (actually called the “shelf”); to position the shelf on the side of the screen; and change the wallpaper, which brings up the Wallpaper tool. Image files saved to the Downloads folder can be set as a wallpaper by right-clicking them and choosing the appropriate option. Beyond this, there isn’t much personalisation , apart from changing the picture that appears by your account name.…

Building security analysis and code analysis into your CI/CD is one of the key means by which we can monitor the quality of your code and any risk exposure. It gives you insight into (and frequently quick wins against) some of the most common vulnerabilities and bugs. The good news is that by adding a couple of small stages to the pipeline you can easily (and in some cases automatically) mitigate entire classes of attack, while also making cleaner code that’s easier to read. The even better news is that most languages and frameworks are already tooled-up and good to go, so you just need to grab the relevant Docker images and very quickly you can be up and running. Having said that, do remember that it’s better to over-estimate…

You might recall the 3.5-inch floppy disks (which had a hard outer-casing so only the disk inside was actually floppy) that could be read by PCs until a few years ago. Before that were five-inch floppy disks, which were genuinely floppy, but the Altair 8800 used the even earlier eight-inch floppy disk. Altair 8800 expansion cards were designed to plug into 100-way sockets on the backplane. Those sockets hadn’t been designed for use in computers, yet MITS’ assignment of the signals to the pins eventually became a standard known as the S-100 computer bus. Paper tape readers weren’t fast at either 110 or 300bps. So, loading BASIC from a paper tape, as you’d have done if you weren’t lucky enough to have a floppy disk drive on your Altair 8800,…

FILE MANAGER KDFM Version: GIT Web: https://sourceforge.net/projects/kdfm Many open source browsers advertise themselves with a ‘browse with style’ motto, meaning that the user benefits from the best experience when exploring the wonders of the web. But why should this be limited to online activities? Your local files and folders deserve better browsing treatment, too! With that in mind, we took KDFM for a test ride to see how it handles file management. KDFM is a KDE-centric file manager designed to be an alternative to Dolphin. It doesn’t have as many features as the latter, but it’s simpler to use, cleaner and more customisable. KDFM is the successor of DFM and a side-project created by the author of the DSP (aka Styleproject) style for Qt5. It imitates Apple’s Finder far better…

A distributed event streaming platform such as Kafka allows you to send messages between processes, applications and servers. Applications connect to Kafka to send or get data. You can learn more about Kafka by visiting https:// kafka.apache. org and www. confluent.io. You can learn more about RabbitMQ at www.rabbitmq. com and at https://github. com/rabbitmq. The command line utilities of RabbitMQ are presented in more detail in www. rabbitmq.com/cli.html. And, you can find the RabbitMQ documentation site at www. rabbitmq.com/documentation. html and lots of practical RabbitMQ tutorials at www.rabbitmq. com/getstarted.html.…

Because Global Interpreter Lock (GIL) is a part of Python and the way Python works, it’s good to learn more about it. GIL is a mutex (mutual exclusion variable) that permits only a single thread to hold the control of the Python interpreter. Put simply, this means that at every single moment only a single thread can be executed in Python. In a world with multiple CPUs and cores, this is not good. So you might ask why do we need GIL. The main reason is to prevent deadlocks, which is a serious issue in multi-threaded programming. The second reason is that back in the first days of Python, computers didn’t have multiple cores, so using GIL wasn’t an issue back then. The main reason that GIL hasn’t been removed…

THE LXF LIBRARY Advanced Bash Scripting Guide Go further with shell scripting. Bash Guide for Beginners Get to grips with the basics of Bash scripting. Bourne Shell Scripting First steps in shell scripting. The Cathedral and the Bazaar Eric S. Raymond’s classic text explains the advantages of open development. The Debian Book Essential guide for sysadmins. Dive Into Python Everything you need to know. Introduction to Linux A handy guide full of pointers for new Linux users. Linux Dictionary The A-Z of everything to do with Linux. Linux Kernel in a Nutshell An introduction to the kernel written by master hacker Greg Kroah-Hartman. The Linux System Administrator’s Guide Take control of your system. Tools Summary Overview of GNU tools. GNU Emacs Manual Six hundred pages of essential information! Producing Open…

A series of vulnerabilities, dubbed FragAttacks, has been uncovered in the Wi-Fi specification that could potentially affect billions of devices around the world. Wi-Fi networks transmit data using a process of frame fragmentation or frame aggregation. FragAttacks, short for fragmentation and aggregation attacks, abuse this process and enable malicious users to insert data into Wi-Fi traffic. It was security researcher Mathy Vanhoe who first brought these vulnerabilities to light. Thankfully, the vulnerabilities, some of which appear to have been present since the creation of the Wi-Fi specification in 1997, can’t be used to extract data, so there’s no risk of passwords or other data being stolen. However, the idea that people could access your Wi-Fi network and the devices connected to it isn’t a pleasant one. Furthermore, these vulnerabilities could…

“For us techies, the cloud has made a lot of things easier. Much of it is built on open source technology. Linux is the most common operating system for public cloud services with a 90 per cent share. Open source databases make it easier to host and manage data. But do public cloud providers support open source enough, and do they provide the right kind of support? It’s no surprise that everyone who responded to our latest survey thought public cloud providers could do more. However, 58 per cent of respondents said competition from public cloud companies who use open source projects but don’t contribute back was one of the top challenges currently faced by open source companies. So, how should public cloud providers contribute to open source? The top…

“A new, low-overhead extension in Mesa means programs can mix OpenGL and Vulkan. This gives flexibility to developers while easing the transition path between the industry-standard Khronos APIs. For the past several months we’ve been working with stakeholders within Mesa to bring the EXT_external_ objects functionality, which enables OpenGL and Vulkan to talk to each other on Chromium OS. The Iris driver, supporting modern Intel GPUs using Mesa’s Gallium framework, was first to receive this support, and was followed by the i965 driver, supporting older Intel GPUs. Implementing this feature enables developers to be able to use Vulkan for their rendering needs while using OpenGL for everything else, and while piglit tests pass, they are by no means a real world use-case. We’re finding corner cases when running applications that…

Modem muddles  Q I live in the US, and I had to upgrade my modem to one supporting DOCSIS 3.1 to access the faster speeds from my cable provider. I have two Linux Mint PCs and two Windows 10 PCs. After changing modems, the Windows PCs would connect to the internet, but neither of the Linux PCs would. I tried two different modems: an Arris SB8200, and Netgear Nighthawk. I called support to my ISP, and the modem manufacturers, but nobody could help. I was never able to get the internet to work, so I had to put the old modem back. After doing that, everything started working again. I kept the Arris modem, just in case someone could figure it out. Larry A Looking for the Arris at the modem…

Each virtual machine you run will take a certain amount of memory, whether it uses it or not, and can be allocated a number of CPU cores. How much of each you allocate affects not only the performance of the VM, but also of any other VMs you may be running – together with the host OS if you take too much. We tested on a system with an eight-core processor and 32GB of RAM, and limited each VM to two cores and 4GB. VMs can either use a dedicated hard disk partition or they can use a file as a virtual disk. We chose to take the latter approach when testing, because that’s the most common method. As such, we didn’t run any I/O speed tests for the VM…

We have mentioned Qemu a few times here, it’s the engine that powers three of these programs. Qemu is command line only, but may be more suitable for some needs. The learning curve is steeper but you do get access to all of its features, not just those that the GUI exposes. Libvirt is another command line option, which is used for managing Qemu VMs and the layer behind Virt-manager. It may be that this program could suit your requirements if a GUI isn’t necessary. It’s also worth considering whether you actually need a fully virtualised computer in the first place. If you’re trying to run software away from your existing OS – perhaps for security reasons – or want different versions of software, then you may find that some…

CentOS 7 was released in 2014 and if you’re still using it you’re safe. Red Hat will honour the original support period and so you’ll receive maintenance and security updates until 2024. CentOS 8 was launched in 2019, with the same stated 10-year support period. So imagine the furore when users of CentOS 8 learned that their OS would instead be sunsetted not in 2029, but at the end of 2021, in order that Red Hat focus on its own CentOS Stream offering. CentOS Stream was introduced in 2019 with the goal of being a truly open source upstream for RHEL. This would bring development of RHEL, which hitherto had taken place behind ominously closed doors, out into the open. When the distinctively unfestive (December 2020) announcement was made that…

The positioning of X has always been at odds with other GUIs. The Apple Lisa, in 1983, was the first machine to ship with such a thing and then something called Windows became awfully popular (we’re not sure why) after its v1.0 introduction in 1985. But both of these GUIs are much closer to the OS than X is to the Linux Kernel. Yes, we know early Windows ran on DOS, but X’s positioning (and the fact that it’s only a low-level part of what most people consider a GUI) has always made it more complicated. Its existence is made even more complicated by the mess of legacies and (probably, with hindsight) bad ideas that it’s inherited. One of the most regretted of these is “mechanism, not policy”. The idea…

Rely on Undo (Ctrl+Z) to explore techniques, but remember that there are a limited number of undo steps. You can increase the number of available steps (Edit> Preferences... >Undo Steps), but consider doing a save (File>Save As...) before trying things out. If you need to use a menu function that doesn’t have a keyboard shortcut assigned to it, you can right-click the menu entry and add it from there. Keys F5-F8 are kept free for the user. In addition, you can use the same method to an oft-used menu entry (press G for fast access). Once you get to know Blender, you may find that you keep making the same changes to the settings, such as the rendering setup. In that case, make the changes in a blank, new file,…

There are plenty of websites that supply textures for free download such as https://ambientcg.com or www.blendernation.com. Find something suitable in PNG or JPG format and then download it. Locate the Material Properties panel and add a new material as described in the main tutorial and add a new material. Click the yellow dot next to the Base Color field, and from the pop-up menu, choose Image Texture. Then press the Open button and select the texture that you downloaded, and this will apply the texture to the object. By default, this is done in a crude manner, and dealing with problems is a complicated subject in itself. However, there’s a quick fix that works in most situations. At the top of the window, click the UV Editing tab. In here,…

Want to try a real Altair 8800 instead of a simulation? The bad news is that it won’t be cheap because these vintage machines are in considerable demand by collectors. However, you can come close to the real Altair experience thanks to the availability of several modern clones. Some still cost more than a cheap laptop that would be phenomenally more powerful, but in real terms they cost much less than it would have cost a 1975 enthusiast. What’s more, if your first experience of computing was back in the 1970s, getting your hands on one of these clones will offer you that proverbial trip down memory lane. One of the best known Altair 8800 clones, ready built in a case that’s a reasonably good replica of the original machine,…

You’ll soon notice that whatever you do with your project, the size of the build directory only grows. At some point, Bitbake takes up all of your disk space leaving you unsure how to free it up. When you build a system image with Bitbake, the dependencies required to build it are recursively discovered and built. That’s not the case for the reversed action, when you use the built-in clean command: This command will only clean the target image files, not its dependencies. However, you can manually delete either unused or unnecesary parts of the build tree, such as: It’s also possible to clean individual packages if you know their exact names using this template: $ bitbake <package> -c clean -f . This is sometimes required if the previous build…

RabbitMQ is a Message Broker, which means that it can safely hold messages generated by applications and make them available to other applications. The main advantages are reliability, support for clustering and high-availability queues, tracing capabilities for troubleshooting tricky issues, support for protocols other than AMQP and the availability of tools and client libraries in many programming languages. RabbitMQ has no tlimit on the payload size, which is important when you have to exchange large messages. The two main disadvantages of RabbitMQ include the fact that it’s written in Erlang, which might discourage some people from extending it, and that it doesn’t support message batching. If you have to choose between RabbitMQ and Kafka (see LXF252), which can both handle message exchanges, you should begin by considering their differences. First,…

The official documentation site of asyncio can be found at https://docs. python.org/3/library/asyncio. html. You can also learn more information about asyncio at https://docs. python.org/3/library/ asynciodev.html and at https:// realpython. com/ async-iopython. A program’s development process should take into account the use of asyncio in order to properly design the application. The extra care and extra code that you write is the price you pay for faster execution time. Bear in mind that not everything can be executed concurrently…

DESKTOP SATORI MIN SPECS: 512MB RAM, 5GB SPACE Bodhi 6.0 HWE We’ve always been fans of stories about humans sitting under bodhi trees listening to Nirvana or however it goes, and we’re also big fans of Bodhi Linux. The lightweight distro sees some big changes with this release, one of which is the lack of a 32-bit edition. Bodhi 5.1 is still covered by the Ubuntu 18.04 support period, so you can still use that on aging hardware (even from the pre-PAE age) until 2023. We were going to put it on the disc too, but storage densities and ISO9660 overheads are harsh mistresses. We’ve gone for the hardware-enablement (HWE) release this time, since the standard release ships with a relatively old kernel. The HWE release uses a 5.8 series…