Indholdsfortegnelse for 101 Cool Linux Hacks - 2021 i Linux Magazine Special Editions

This Linux Magazine special edition promises you “101 Linux hacks,” and we’ll certainly deliver – check the table of contents on the following page for a list of all the gems we present inside. But what exactly is a “hack”? In today’s world where Windows is the dominant desktop operating system, the decision to use Linux is the first and most important hack. In addition to that: ■ If I can use it to solve a problem or get some work done faster than before, then it’s a hack. ■ If the way it works is unexpected, it’s very certainly a hack. ■ If it teaches me a new and interesting way to use my Linux machine, it’s a hack. ■ When it makes me grin, because it’s so obvious…

If you work from home, or work for yourself, a time tracker is an essential tool that can not only help with productivity, but help when it comes to invoicing clients, estimating the timing and velocity of a project, and tracking your own efficiency. But to be effective, a time tracker has to be as efficient and as transparent as possible. In particular, it needs to be as simple as possible. Too complicated, and the effort required to maintain a log, or context switch between your work and your time tracker, makes the tracking process itself inefficient. This is especially true if you’re working on the command line and need to switch to a GUI. This makes Chrono ideal. Chrono is a command-line time tracker that offers a comprehensive set…

Every admin knows how to retrieve information about the system on which they are working. How many cores does the CPU have? cat/proc/cpuinfo! Is eth3 a gigabit interface? ip l sh! But instead of many tools, you can just use one: inxi. It is available via many package repositories (e.g., openSUSE, Debian, Ubuntu, and Linux Mint). Suppose I need an overview of a machine with which I don’t normally work. Then, I call inxi without any parameters and get some basic information about the hardware (CPU, clock speed, RAM, and disk size) and the system (kernel and shell processes). If I want to see a few details, the -F parameter provides information on the video and audio hardware, partitioning, Swap, temperatures, and fan speeds (Figure 3). If I’m only interested…

The dmesg tool shows messages that appear in the “kernel ring buffer,” and it can do so in many ways as the impressive list of options in its man page shows. But most of those options aren’t interesting; you just need a few. Run dmesg -HTwx to see both user-level and kernel-level messages with a human-readable, absolute time format (-HT), as well as priority prefixes (-x) in continuous/follow mode (-w). That leads to the situation shown in Figure 18. The color highlighting appears automatically unless you’re remotely logged in from a terminal with strange settings; in that case, you can try to force colored output with --color=always. While this lets you look at the screen and wait for future messages, you cannot scroll back. If you want to see the…

When you delete a file in the file manager, it does not exactly disappear. In most cases, it falls into the recycle bin, from which it can be quickly restored. But even if you empty the trash, the supposedly deleted data can still be reconstructed. Linux supports two console tools, shred and wipe, both of which securely delete files, directories, or entire partitions. In practice, however, you will rarely want to launch a terminal to wipe a file off your hard disk. File managers can be equipped with similar functions. For example, Gnome Files (formerly Nautilus) has Nautilus Wipe, an extension that lets you securely delete files with a single mouse click. (For KDE, the Secure delete service menu adds the same functionality to Dolphin.) After installing the package (nautilus-wipe…

GNU PrivacyGuard (GPG or GnuPG) is a cryptography tool that lets you send and receive encrypted mail. It also comes preinstalled with every Linux system – but not preconfigured for email. Sadly, there is no out-of-the-box tool that you can install and automatically have all your communication secured. Sender and receiver have to use the same encryption protocol, and in the case of GPG, some further preparation (key exchange) is needed before they can open an encrypted mail channel between the two. Using a keyserver (such as keyserver. ubuntu.com or pgp.mit.edu), you can search for public keys (Figure 4) and import them into your GPG client. GPG users often put a fingerprint in their mail signature so that it’s easier to find their key. Once you’ve imported a person’s public…

Protecting your own websites from attack either costs a lot of money or requires a lot of expertise. A specialized Linux environment called Web Security Dojo offers an easy way for everyday users and beginning professionals to learn about web security. Dojo is designed to provide practical, hands-on exercises on web security and intrusion techniques. On SourceForge, you can find a virtual machine (VM) image of around 3.9GB in OVA format that works with both VirtualBox and VMware; it is based on Xubuntu 18.04.4 LTS with an Xfce desktop. When you launch a browser in the VM, you learn about the software you’re going to attack: Damn Vulnerable Web Application (DVWA). From a menu, you can pick various attack technique options, such as Cross Site Scripting (XSS), SQL Injection, CSRF,…

Network monitoring isn’t easy for everyday users. If you’ve ever taken a look at the packets captured by Wireshark, they’re incredibly complex and difficult to understand. And so too are the associated command-line tools. It’s easier for distros to keep users at arm’s length, letting them worry about wireless network strength and streaming quality rather than presenting users with a stream of data that’s difficult to interpret. But much like with a task manager or memory monitor, there are many good reasons for ordinary users to be better informed about their network consumption. Nutty is a network monitoring tool that will attach itself to one of your interfaces, such as your wireless connection, and then perform a series of monitoring processes or tests. Ubuntu users will need to install from…

The wormhole tool mentioned in Hack 46 is perfect for one-off transfers, but it’s not all that great if you want to share more than a single file or leave the tunnel open so that you don’t have to keep renegotiating keywords. There are lots of ways this can be done, but weborf remains almost as simple to use as wormhole. weborf (Figure 9) sets up a simple HTTP server, just like running Apache in the olden days to share the contents of/srv/www. This makes it supremely flexible, not just from a web browser, but from almost anything with access to the network using WebDAV, with caching, even from virtual hosts or running CGI scripts. You simply run the server command with an argument for the port to use (-p…

While playing with a virtual machine, I came across a strange problem: Each time I ran a command via sudo, there was an artificial delay of about two or three seconds. After some Internet searches and a confirming look at the source code, I found out that the sudo tool queries the hostname of the machine on which it is running, and that operation may cause a delay when you have mismatching information in your network configuration files. When you notice inexplicable delays, check the contents of some of your configuration files – even if you don’t think the problem is network-related: • /etc/hosts should have an entry for your hostname – either pointing to 127.0.0.1 (in that case it will be placed on the same line as the localhost…

Linux users often have to deal with file archives in ZIP, RAR, or compressed tarball (tar.gz, tar.bz2, tar.xz) formats. The commands for unpacking these archives are as different as the formats: unzip, unrar e, and tar xf. The tar command, in particular, regularly challenges users with its cryptic syntax. Especially annoying is an archive full of files that are not stored in a separate subdirectory when unpacked but instead clutter the current folder. Such shortcomings are addressed by the dtrx unpacker – the abbreviation stands for “do the right extraction.” All the popular distributions have dtrx in their package sources; under Ubuntu, the installation includes a number of tools for unpacking. On the other hand, with Arch, you have to install the necessary tools yourself. As a wrapper, dtrx is…

Linux distributions come with many terminal emulators to choose from: If you run KDE, the default is Konsole; on Gnome it's Gnome Terminal. Most other desktops have their own special programs, too, and some purists like to use good old xterm. In addition to regular terminal programs you can find specialized ones, such as the Quake-console-like terminals that roll down from the top when you press a key and hide when you press it again: Guake (for Gnome) and Yakuake (KDE) are two of these. Cool Retro Shell belongs to a third category: fun terminal emulators (and it's the only such program I'm aware of). This app brings back the look of the old monochrome CRT monitors – it’s all there: the curvature in the corners, the scanlines, and all…

When I’m navigating through my folder hierarchy, I tend to find files that I cannot remember creating – and the file name does not help either. I want to look at the contents (and possibly decide to delete the file or move it elsewhere). If this sounds familiar, then how do you open such files from the command line? You could launch the right application from the desktop’s program menu, use a command like echo $PWD/filename to find the full path of the file, and paste that into the opening dialog. Or, if you happen to know the file name for the program binary (like soffice for LibreOffice), you can type soffice filename. In most cases, your desktop knows which applications could open your files: Double-clicking them in the file…

If you create lots of videos, such as screencasts of your desktop (see hack 68 featuring Peek), you often need to cut bits out of them. That’s an essential part of both the recording and editing process. Editing is obviously the central process in all video editors, but often all you want is the video equivalent of selecting a piece of text and pressing delete. VidCutter aims to do just that: make practical edits quick and easy. The UI is refreshingly simple. Most videos load without conversion, thanks to the libmpv back end, and you can immediately start playing with the edits. The basic process mimics that of fully fledged editors while restricting options to a minimum. You go through a file creating clips by selecting the start point and…

Online book sellers and the self-publishing revolution have changed the publishing landscape for book authors. No longer are the keys to the printing press held by the few, and success is no longer limited to those with a publishing agent and book deal. In the 21st century, anyone can publish anything. There are obvious negatives, too; there’s a lot of rubbish out there, and the ratio between poverty and success is similar to that of winning the lottery. But it is possible, and success can be measured in many different ways. There are a few things you need if you’re going to publish your own book, apart from the talent, drive, and commitment to write the thing in the first place. The first is a decent writing environment. This is…

Turning off your Linux computer by cutting off the power is a bad idea: The system wants to shut down properly so that it terminates all running processes and unmounts the filesystems. If you simply pull the plug, you risk losing data or corrupting the filesystem. Thanks to journaling, the repair procedure is quick, but you still should avoid a hard shut down. However, sometimes a regular shutdown procedure takes too long. If you need to leave a room very suddenly and take your machine with you, waiting that one minute until shutdown -h now completes may not be an option. Maybe you have already heard of the magic SysRq key – it can help you. If enabled, Linux responds to key combinations that begin with pressing Alt+SysRq. (The SysRq…

Even if you’re not a developer or a “hacker,” sooner or later you’ll need to use a hex editor. This is primarily because a hex editor is a bridge between the worlds of code, binary, and content, allowing you to open and view a file regardless of its format or whether the file is corrupt or complete or not. The file could be an executable binary in which you search for some string. A hex editor will gladly display any file’s contents where a classical text editor won’t. That display usually defaults to hexadecimal values, or base 16, representing the raw binary contents of a file. Thanks to your computer’s binary logic, this single hex value is a “nibble” of data, usually grouped into pairs to form a “byte.” Bytes…

Tools for navigating git repositories, their history, and their branches are becoming almost as common as CPU monitors. And like CPU monitors, they also happen to be very useful. Having more options to choose from means you’re more likely to find a tool to fit your exact requirements. One fully fledged option is GRV (see Hack 86), which runs from the command line and features several different view modes. At the other end of the feature spectrum, gitin is another great option. Unlike GRV, gitin isn’t an application in which you spend time; instead, it works best as a form of wrapper around the git commands you might use anyway. Its principle functions allow you to work with branches, check the status of a repository, and view the logs, which…

Those of a certain age will remember a time before the Internet: If you wanted your computer to communicate with other computers, you did it on a 1:1 basis across a telephone line. You dialed a number, and another computer answered before proceeding to negotiate a stream of ASCII going back and forth down the line. There were many popular “online” services that you could pay to access, but perhaps the best use of this technology was the humble bulletin board system (BBS). These were portals for files, messages, and games that were usually run from a home computer with nothing more than one or two phone lines that became available in the middle of the night. The Internet killed the BBS scene, but it’s now having a slight renaissance,…

Look at Figure 7, which shows good old EDIT from DOS editing a file. If you want to replace all other editors with this classic tool, there’s a way. To prepare, first install DOSBox (the dosbox package) and create a dos folder in your home directory. Then grab an image of a MS-DOS clone, such as FreeDOS 1.2. Mount the CDROM image (FD12CD.iso) and unpack the BASE/EDIT.ZIP file into/tmp. You will find a new BIN subfolder that contains EDIT.EXE and EDIT.HLP. Copy those to ~/dos. Also copy the text file you want to edit to ~/dos/file. txt. Now you can boot DOS and let it execute EDIT.EXE by typing: which brings back the glorious old look and edits your file. You can access the menu entries by pressing Alt and…

A default KDE Plasma desktop has a panel at the bottom of the screen, a start button holding menus at the bottom left, and a tray on the right – all quite conventional, boring, and even Windows-y (see Figure 4). But Plasma can be configured to look like anything, even like Ubuntu’s defunct Unity, Gnome, macOS, or whatever else rocks your boat. Both Unity and macOS use a global menu: It is the menu that appears in a bar at the top of the screen and shows a selected application’s options, instead of having them in a bar along the top of the application. To create global menus in Plasma, first right-click in any free space on the Plasma desktop and select + Add Panel | Empty Panel from the…

Do you work with virtual desktops? If not, try them. Assuming that you do more with your Linux machine than run a browser, a mail client, and LibreOffice, it is likely that your desktop becomes cluttered with windows. Maybe you minimize some of them to get the chaos under control. Connecting one or two extra monitors would improve the situation, but that requires free space on your desk (and money). Instead of physical, go for virtual. Linux desktop environments like KDE, Gnome, and most others have a feature called virtual desktop. You can have two or more independent areas where you can place your windows. There’s no need to minimize them; just spread them out on as many desktops as you need. KDE On KDE, press Ctrl+F2 to reach a…

I like empty partitions: When I install a new Linux distribution on a test machine and log in for the first time, I sometimes take a look at the empty Documents folder and think: How beautiful! Let’s put two or three files in that folder and enjoy the clarity. On my real computers, things are different. The following code was run on a notebook that holds only some of my files: (If you like what this command does, put it in a shell script.) Creating or collecting thousands of files means trouble when you need to find one of them. Linux gives you a few built-in options for searching, so you might want to start with them. By cleverly combining shell commands such as • ls -lR (recursive listing)• grep…

Experts agree that you should keep a copy of your data, but restoring from incremental backups takes time and sometimes doesn’t work as expected. Alternatively, you can clone the partition. Several tools help with that job; we suggest you use Clonezilla even though its text-mode interface looks outdated. Cloning software differs greatly from backup software. Partition copies cannot be supplemented and accelerated by differential or incremental partial backups. Admins can thus reconstruct the complete system in a single pass in case of a crash. Unlike a backup solution, a clone does not require importing several backup layers. The best known example of cloning software is the free live system Clonezilla. Developed in Taiwan, it is based on Debian Sid or alternatively on Ubuntu 21.04 and has no graphical user interface…

Sometimes things go wrong when you are installing an operating system on a hard disk drive or SSD. A boot repair disk gets your boot configuration back on its feet, quickly. The boot process for computers has become massively more complicated in recent years. Unified Extensible Firmware Interface (UEFI) has largely replaced the traditional BIOS, while increasingly large storage devices require new types of partitioning. The configuration options of bootloaders such as GRUB 2 have thus been massively extended; even minor changes to the system can cause startup problems. In the worst case, you will be left sitting in front of a black screen with a flashing cursor without the operating system having booted. In this situation, Boot Repair Disk provides invaluable assistance: The operating system, based on the lean…

There are many command-line system monitor tools, but there’s always room for another monitor that attempts to do something differently. Hegemon succeeds, mostly, because it presents only the information you really care about in a way that’s useful. That information is how much of your CPU capacity is being used (broken down into cores, if required), how hot your system is running, and how well your fan or cooling is responding to this load. It presents this information as a scrolling and colorful histogram that can be expanded or contracted with a simple press of the space bar (Figure 16). As system load increases, you can see exactly which cores are carrying the burden, along with how it’s heating up your system. The fan speed will typically ramp up to…

A computer’s webcam and microphone are often abused for attacks and privacy violations. Thanks to modern web technology, such as HTML5 with WebRTC, a browser is all it takes to transfer the image and sound from your living room to the web. For example, video chats with AppRTC can be handled directly in the browser (Figure 3); a web page could also tap the webcam for other purposes. Although a browser requires the user to confirm that the website is allowed to enable the webcam and microphone, errors (on the part of developers, as well as users) occur time and time again. And with a locally installed application – installed voluntarily or by a trojan – you might not even be prompted to confirm. Apart from a small light in…

The sudo command has been around since the 1980s, but it has gained popularity in recent years as the default tool for running commands as root in Ubuntu. However, there’s far more to sudo than Ubuntu’s policy. In fact, sudo‘s man page is over 700 lines long, covering a staggering number of situations – some of which, like many powerful Linux commands, can get you in a lot of trouble if you are careless. sudo also offers options that can greatly enhance security, especially if you take the time to be creative. Why would you want to enhance your security? The answer is that, from a security standpoint, Ubuntu’s use of sudo can be viewed as a problem (although opinions do differ). As you may know, when sudo is configured…

There are obvious situations when you should lock your screen, like when you work in an open-plan office, you have opened four terminal windows with remote root shells on various machines, and you’re just about to leave for an extended lunch break – you don’t want the computer to stay accessible. During my time as a postgrad, it was a running joke that co-workers would enter each other’s offices, search for unlocked computers, and open a website like lockyourscreen.com (Figure 8). Of course, that’s better than quickly installing a backdoor SSH server. But even in less dangerous situations, it makes sense to lock the machine; if you’re at home and have a cat who likes to walk across the keyboard, it may provide just the right input for the vi…

Magic Wormhole really is one of those tools that, once you’ve used it, you’ll wonder how on earth you managed to get by without it. This is because Magic Wormhole solves one of those ancient problems that have been around on Linux since we first started to connect computers together with null modem connectors and a couple of lengths of wire. Back in those olden days, you might have used ZMODEM to transfer a file across the serial connection. If you then upgraded to a connection capable of TCP/IP, you could use FTP to transfer files and then came HTTP. In the modern age, scp is often the best choice if you’re accessing an SSH server and want to securely transfer files, or rsync if you want to copy folders…

Network Manager, the configuration tool used by most current distributions, comes with a command-line program called nmcli (which is short for the obvious: Network Manager command-line interface). It lets you query some interesting data, including available WLAN access points (Figure 16). When you’re in a new place like a hotel and you’ve received a paper slip with an SSID and password, you can use nmcli to connect without going through a graphical dialog. Just type (with SSID and PASS replaced, of course). You need not add sudo, because the tool connects to a daemon that has the necessary privileges. Actually anyone who is logged in to the machine can use nmcli or any other program that talks to Network Manager – for some tasks it will explicitly request root privileges…

There are few tools more effective than the venerable top command for process monitoring and control. This is because it can be run from almost anywhere that has a Linux command line and gives you an immediate and realtime overview of what processes are running; how much memory, swap, and CPU they’re consuming; and the ability to kill a process by simply selecting it and issuing a command. Except that top is perhaps a little too venerable at times, with its minimalist and austere user interface written for 1984-era Unix rather than the cloud droplets of the 21st century. htop is a drop-in replacement for this fabulous command. htop adds lots of features lacking in the original, and its developers occasionally release new versions to make it adapt to new…

The default shell on Linux is Bash, but there are some classical alternatives like Zsh or Csh. The fish shell is yet another shell, but it’s different from all the others. Fish offers some very helpful command-line completion features. For example, when you start typing a command, you get suggestions for old commands from your history. The shell shows how the letters you typed so far could be completed to form your old command, with the missing bits in light gray, so you know what’s already there and what’s a suggestion. Press the Up arrow key to go back to older history entries. Or press Tab to see which binaries in your $PATH start with the letters you entered so far. If there are many possible completions, fish will only…

Draw.io has been around for years as a website. If you ever need to draw a diagram or flow chart, or even a circuit, it’s indispensable. Many users now rely on it for their last-minute presentations, their documentation projects, and project planning, because draw.io’s great strength is that it offers many different symbols in many different categories, making it capable of drawing many different kinds of charts. You don’t have to create your own icons, steal images from the Internet, or rely on Inkscape for your arrowheads. Instead, you simply drag and drop symbols, join them together, and then use draw.io’s wonderful styling, arrangement, and node options to create a final file that you can save online or locally. The only downside is that the website version requires running it…

Some documents that I create in LibreOffice Writer are “throw-away” documents: I type a few lines, add some quick formatting, print the document, and then save the file or just close the program and discard it all. That’s the one case where it doesn’t make sense to work with styles. But most documents are different: You create them one day, and weeks, months, or years later you edit them again or create a copy to which you add new text. The longer those documents become and the more they are structured (into chapters, sections, etc.), the more it becomes vital to format them with proper styles. For example, automatic generation of a table of contents is only possible when you’ve assigned a headline style to every headline. Using styles also…

Yes, there are many, many text editors for Linux. But there isn’t a Linux equivalent to the venerable Notepad++ on Windows. Textosaurus attempts to fill the void. Thanks to being built on both Qt and the Scintilla text-editing framework, it’s completely cross-platform, so it can replace Notepad++ on Windows as well as it does on Linux. It even features a very similar layout and design. To help with its cross-platform credentials, it uses UTF-8 internally, so your text should remain legible whatever platform or locale you’re using, and many input encodings are supported. It also features menu options to convert end-of-line characters into something that works, which is often still a problem when working with text files generated in Windows. The syntax highlighting looks fantastic and will even print, while…

When viewing binary files in hexadecimal, you’re able to decode more than the literal value for any one location. You’re actually able to see patterns and even raw data emerge because the view can represent the way data is physically passing through memory. This is why a hexadecimal viewer is an essential utility to have at hand, especially if you’re interested in how files are stored or how an executable may work. One such tool, hexyl, couldn’t be any simpler (Figure 6). It’s driven from the command line and takes a filename as an argument. The only other potential argument is a value to adjust the number of bytes read from the input. This is useful if you’re trying to view something large, such as a swap file or even…

Are you interested in statistics about your coding projects? You could process your source files with wc -l to get a line count, but that simple tool does not know the difference between comments and real code. We suggest that you use something better. cloc – which stands for count lines of code – gives you an overview of your projects. The practical helper counts blank lines and comments, as well as real lines of code (Figure 8). It writes the statistical analysis to the standard output. cloc requires Perl 5.6 or later. On Ubuntu you can apt install the cloc package; on other distros use git clone. cloc understands more than 250 different programming languages. You can obtain a full list using cloc --show-lang. You can specify individual files…

The nmap (network mapper) tool searches for open ports in a computer network or on a specific machine, and it can even find out which operating system and version is running on a remote computer. That makes it an important tool for IT professionals with a security focus – as well as for hackers gone bad who attack machines for evil purposes. The second group includes script kiddies. True script kiddies like to see their texts in leetspeak (or l3375p34k). Since they are likely to (mis-)use the nmap tool, it provides a leetspeak option to make them comfortable. You can feel like a script kiddie, too: Just run the mapper with the option -oS to change the output format to “Script kiddie” – the result will look like Figure 3.…

While it’s sad when a company gives up on gaming, if they choose to do the right thing with the code, it benefits a much wider audience. Star Ruler 2 is a great example (Figure 6). A popular real-time strategy (RTS) game from 2015, it’s still available on Steam, but the studio behind it, Blind Mind Studios, has been inactive for a few years. Rather than drop off the radar completely and alienate its players, the studio decided to open source both its game and the expansion pack. You can install the game with just a single command, sudo snap install starruler2, if your system supports snaps. You get a major multiplayer RTS title on Linux for free, and that’s never a bad thing. Set in space, the game itself…

Reading a good book is always worthwhile, but computing literature tends to age in a way that makes most practical descriptions obsolete within a decade. In the case of Linux, that doesn’t happen to all documentation. While a KDE book from the late '90s has lost all usefulness (except as a picture album to see what desktops looked like in the old days), you can always grab a good introduction to the shell – for example, the article “The UNIX Shell” from Stephen R. Bourne, who developed the Bourne shell (sh), an ancestor of the Bash shell. After all, Bash is an acronym meaning “Bourne-again shell.” The article was published in 1978. Grab a copy from archive.org and read the introduction to using the shell, working with variables, writing shell…

Many applications let you zoom the content they display; for example, in Firefox and LibreOffice, you can press the Ctrl key and move the mouse wheel to increase or decrease the zoom level. But sometimes you may need a different kind of zooming. Imagine for example that you show a Libre-Office Impress presentation to your audience, and there’s a detail you want to draw attention to on your slide. You’ll have to leave presentation mode and zoom into the slide in Impress’ editing mode, which is not really professional. Luckily, it is possible to zoom the whole desktop. Depending on your desktop environment, you may have to activate the feature. Cinnamon Can Do It, Gnome Almost If you use Cinnamon, open Preferences | Accessibility and click on Enable zoom. Then…

Sometimes you don’t want your computer to start the screensaver (and possibly lock you out) or activate some energy-saving mode and suspend. For example, I used to get very annoyed when I brought my notebook to a classroom and stepped away to explain something on the blackboard – only to find a few minutes later that the beamer no longer showed my presentation slides. For me, that’s a problem of the past, because I use Caffeine. There are several tools with that name (including ones for macOS and Windows); pick the right one for your desktop! If you work with KDE or Cinnamon, you can install the caffeine package (do not confuse this with Kaf-feine, a KDE media player). Then run caffeine-indicator (if you like it, add it to your…

Install and use Zim, a handy tool that enshrines the principle of the wiki on your Linux, macOS, or Windows desktop. The word “wiki” comes from Hawaiian and means “fast.” The term refers to a system in which HTML documents on the Internet are both read and edited using a web browser. The most prominent example of a wiki is the Wikipedia online encyclopedia. Other wikis inhabit both large and small projects within the open source universe. Many wikis are used for documentation purposes. Debian, Ubuntu, and Arch Linux are known for their comprehensive wikis. A wiki’s main task is to organize content in a structured way. Many of the popular wiki tools are designed for collaboration over the network, but the wiki concept also provides benefits for a single…

One of the biggest compromises you make when you forgo the privacy infringement of online photo storage is convenience. Not only is online storage usually limitless and cheap, it’s typically combined with the same clever AI-generated search metadata that drives whatever online platform you choose. Google, Apple, and Amazon, for example, all silently trawl through your uploaded photos to recognize common items, colors, locations, situations, and of course, faces. This can really help you find a single image in a collection that might have started over a decade ago, and it’s a process that can’t be easily replicated on a local machine with local storage and no access to the cloud. Until now. DigiKam 7 is the latest release of KDE Plasma’s flagship photo manager, a photo manager that also…

Many years ago, when computers were big and heavy and their screens were bigger and heavier, you might have had more than one machine. If you did, you really wanted to avoid having more than one screen. The best solution for this was a KVM switch – not to be confused with the now more commonly used acronym for kernel virtual machines. A KVM switch connected a single keyboard, a single video device, and a single mouse to one or more machines, with a physical or software-controlled switch that was used to flip between controlling any of the connected machines. It saved space and time. But there was another clever solution that needed no clunky hardware, and that was a piece of software called Synergy. With Synergy, one machine would…

Half of the Linux administrator’s life is entering commands in the shell. The other half is editing files in the vi editor (or its improved version, Vim – which stands for vi improved). Rumor has it that there are alternatives to vi, names like Emacs, MCEdit, Gedit, Kate, and nano come to mind. Don’t worry, this hack won’t take part in the famous “Editor War.” If your preferred editor is not vi, then let me only suggest that you learn the basics of this ancient tool that – according to its Wikipedia page – has been around since 1976. Why should you do that? Here are my favorite reasons. • vi is not only available for every operating system, it is also preinstalled on every Unix-like system. So if you…

Many users use GNU ddrescue to save data from a faulty disk. However, the resulting logs are difficult to read. ddrescueview graphically processes logfiles. In order to use it, run ddrescue with a third file name argument so that it creates a “map file.” Then open that file in the viewer program (File | Open mapfile). First, the tool determines the disk size and displays an overview of all sectors in the main window (Figure 17). The different colors represent how a section is doing and whether the tool was able to save it (green), it is defective (red), not trimmed (yellow), or not yet recognized (gray). You can receive detailed information about a sector via a mouse click: This will open the Block inspector dialog, which reveals where the…

Do you like how searching for a new TV online will fill web pages with ads for just that product over the next few months? If not, you may want to stop Google and other ad sellers from tracking you. That’s not so simple: You need to switch to a fresh IP address for every new website you visit, block cookies, and more. Tor and Tor Browser combine all the tricks currently available for secure and private web browsing. The actual browser is a Firefox version that’s been preconfigured to use the Tor network. Install the torbrowser-launcher package (via apt install on Debian/Ubuntu/Mint, dnf install on Fedora, and zypper in on openSUSE) and then run the torbrowser-launcher command from inside a terminal. If used for the first time, the tool…

There are many ways you could encrypt a file before sending it as an email attachment or uploading it to some cloud storage service, and most of them will need some amount of preparation or contain needless steps. For example, sending the attachment in a GPGencrypted email requires you and the recipient to have GPG installed and configured, and you need the other party’s public key. Putting the file in a password-protected ZIP archive is an option, but why create an archive when you have just one file to send? The command-line tool ccrypt provides a quick solution. It is available from most distributions’ repos, so apt install, zypper in or dnf install the package on your machine. For encrypting a single file, type ccrypt filename. The tool will ask…

Practically every admin uses the classic traceroute tool at more or less regular intervals. This gets me all the more irritated when I find myself in a hotel with a WiFi network where the admin has completely disabled ICMP. Apart from the fact that this causes more trouble than benefits in what is by definition a public network, it can be easily circumvented. The first version of traceroute was written in 1988 by a certain Van Jacobsen – Van is his first name, not an honorific. To be able to trace the path of packets through the web, Jacobsen came up with a clever method. He sent test packets through the Internet to a defined destination and increased the time to live (TTL) value for each packet. The first packet…

Your parents or friends have replaced an unmanageable Windows installation with an easy-to-use Linux variant, and they have designated you as their remote admin. To access the system from afar, you resort to a GUI-based tool such as TeamViewer or AnyDesk. All is well until the GUI for the computer you need to access breaks. Suddenly, your GUI-based remote access tool won’t work anymore, because you don’t have access to an X server. Tmate, which stands for “team mate,” offers a convenient solution for remote access in situations when you can’t depend on the graphical tools. This fork of the popular tmux terminal multiplexer has significantly more functions than the original. Tmux is functionally similar to screen (see Hack 49) in some ways. You can use tmate to create and…

Most tasks are repetitive: You enter the same directory, open the same file in your favorite editor, and query your dynamic IP address once again. Typing the required commands again and again would be annoying, but often you won’t have to do that: The shell remembers your commands and stores them in its history – both in memory and (when you exit the shell) in a file in your home directory. Accessing the history is as simple as pressing the Up arrow key: Each keystroke will travel back further in time and show the last command, the second to last one, and so on. When you have found the right command, either press Return to run it again or edit it (like you would edit a freshly entered command with…

We don’t often consider the speed of terminal emulators like Konsole or xterm. The commands we run in them are nearly always the culprits when it comes to clogging up the system, but that doesn’t stop developers from trying to create the fastest terminal in the land. This is what Alacritty is – a terminal emulator that promises “blazing fast” speed. It’s even brave enough to claim to be the fastest terminal emulator available, and I certainly found it faster than anything I had installed. But the clever part is that this speed comes from a part of your system you’re unlikely to be fully utilizing while typing on the command line, and that’s your GPU. Alacritty uses OpenGL directly to harness the power of your graphics hardware and is…

Despite the World Wide Web demanding more and more of our systems, many of us just want a simple browsing experience that neither detracts from the information we want nor diverts system resources. For this reason, a web browser running in a terminal window is very attractive. Ideally, it would focus on the text and ignore both the images and wider site design, letting you read and download only the parts that matter. This would be brilliant if you’re also on a low-bandwidth connection or connecting via SSH to a headless lowpowered server such as a Raspberry Pi. But the absolute minimalism of console browsers like Links, Lynx, ELinks, and w3m is often too much for a modern site, both in the way their limited rendering makes a complex site…

When you’re working in the shell and you type bash, nothing happens – apparently. The shell prompt returns at once, and you can continue to enter commands. But when you try to run a command from the history, you will notice that it is somehow outdated (and especially the bash command that you’ve just typed will not appear in the history). That’s because you’re no longer working in the shell that was active when you typed the bash command: You have started a sub-shell in a child process, and the original shell has been suspended until you leave the new shell with exit. Running ps --forest will reveal the parent-child relationship of the two shells (Figure 18). But what is that good for? Working in a sub-shell is a good…

A screencast shows what happens on the desktop. Peek lets you create screencasts in the blink of an eye and export them to popular formats. Compared with other screencast tools, Peek has a very small feature set, but the program is not trying to compete with the more established applications. Originally, it simply recorded the desktop as a GIF, thus producing videos that were easy to embed into web pages. However, Peek now also supports more traditional video formats such as WebM and MP4. In terms of the interface, Peek is deliberately oriented on the LICEcap screencast tool for Windows. The program shows a scalable transparent window that is always in the foreground on top of all your other applications. Everything inside the window frame is grabbed as a video…

Brackets is an open source text editor targeted at web design. There’s obviously a Linux version, but the part that makes Brackets unusual is that it’s been developed by Adobe, and they worked on it from 2014 to 2020. Even though the code is now orphaned, it’s worth trying out because Brackets is rather brilliant. The first thing you notice when you launch the application is that it looks nothing like a typical Adobe application. It actually looks good, and its user interface doesn’t impinge on usability, with a large text pane holding the editor itself, complete with beautifully rendered text using whichever font you prefer. Start typing into an HTML document, and the autocomplete helps you start and finish elements, fixes indentation, and subtly highlights the tags from the…

httpstat is a special stopwatch you can use to discover how long web servers take to serve a page: Visible performance lags indicate optimization potential. The Python script wraps itself around curl. Apart from Python 2 or 3 and curl, it has no other dependencies. You can retrieve it from the GitHub repository and call it using python httpstat.py <URL>. If the Python installer pip is present on your system, you can use that to install httpstat and call it directly by its name. While you can leave https:// out of the URL, you must specifyhttps:// for web pages secured with TLS. Figure 8 shows httpstat measuring an unencrypted call. Four milliseconds for a DNS reply is a really good value, but I cheated: The name is in my local…

You may know the mount option --bind (or -o bind) that lets you mount some directory to a second place in the filesystem hierarchy. We’ve also used it in the previous hack (which used chroot to jump into a different distribution). While classical bind mounts are often useful, the feature is not very flexible and also requires root privileges. bindfs, which is a FUSE-based filesystem driver, lets you perform bind mounts in much more flexible ways. You can grab and unpack the source code and then run make to build the binary, or – if you’re lucky – install a package from the repositories. In my tests, there were bindfs packages in the Ubuntu 21.04 and openSUSE 15.3 repos. As a first example, the following will give you an alternative…

Sometimes you want to use functionality that is familiar from C programming, but you cannot find a corresponding tool that you could call from a shell script. For example, the getsid() and getpgid() functions (which return the running task’s session and process group IDs) have no shell programming equivalent. Of course, you could write a small C program that calls the function of interest for you, but then you’d have to include parameter evaluation. A better way is to use a simple wrapper script that takes a string of C code, puts it into a C source code file, and then compiles and runs it. The following five lines do just that: Save this file as ~/bin/runc and make it executable. (Use a different filename if you use the opencontainers.org…

So many of us now use git on the command line that it’s difficult to contemplate using a GUI tool to make accessing git repositories easier. The context shift from command line to desktop is often enough to break your train of thought or concentration, but there is a helpful tool that’s worth using: Git Repository Viewer (GRV) effectively builds an entire GUI on the command line around your local git repositories. The main view, called the History View, consists of three panels (Figure 4). On the left is a pane for branches, tags, and remote references, and in the middle is a list of commits for your chosen branch. The pane on the right side lists the changes, as a diff, for that specific commit. The other view is…

Not many other software categories offer such breadth of choice as text editors. Textadept is one promising speed and distraction-free design without sacrificing essential features. It is available for Linux, macOS, and Windows. Textadept is certainly mature: Its development started in 2007, and the developers have released a new version every two months throughout the past ten years. Textadept can be run either as a curses binary within the command line or as a GUI application. The executable is around 3MB and can be run off a USB stick. Into this tiny space, it’s not only capable of cramming in lightning-fast syntax highlighting (for around 100 languages) but, more importantly, code completion, too. For those of us without photographic memories, this feature is essential. Autocompletion via Ctrl+ Enter works with…

When you think of games made with ASCII characters, you typically start with Snake and end with NetHack, both of which are brilliant in their own way. You don’t typically think of something with refined arcade-quality playability and design. And yet that exactly describes Ascii Patrol, an interpretation of the arcade classic, Moon Patrol, recreated in text characters to run on a console. Outside of '80s-era home computer arcade conversions, it’s one of the few modern recreations of an old game built atop an even more limited graphics engine than the original. However, in this case, it makes the graphics utterly enchanting. You’ll be hooked from the moment you launch the game and the moon buggy scrolls smoothly from one side of the screen to the other (Figure 4). On…