Linux User & Developer的No. 173目录

This issue » Sysadmin survival skills » Bug-sweep your code » Program in Erlang » Ulimate distros and FOSS 2017 Welcome to the latest issue of Linux User & Developer, the UK and America’s favourite Linux and open source magazine. Ready yourselves for boot-up camp, troops, as we explore the sysadmin survival skills you’ll need in the wild. In our feature on p18 this issue you’ll learn the essential tools and techniques you need to manage file systems, users, permissions, optimisation, troubleshooting and more. Whether you’re a sysadmin right now, you’re looking to become one, or even if you simply want to take complete control of your home network and everything on it, our yomp through the essential training you need will get you fighting-fit. Also this issue we take…

The fantastic SUSE Linux Enterprise Server OS has recently got an official port for the Raspberry Pi 3. Based on the ARM version of the OS, the port will cater for the Model B SBC and will also work in tandem with the Pi’s integrated Bluetooth and Wi-Fi functionality. In an official report from SUSE, a spokesperson said: “Yes, we actually took the enterprise grade, 64-bit, Linux operating system that is used around the world to support mission critical workloads in financial institutions, air traffic control centres, manufacturing centres, and high performance computing centres – and put it on a $35 credit card-sized computer.” Under the hood of the port, Btrfs has been introduced as the root file system, while IceWM is used as the default desktop environment. For end…

“Linus Torvalds announced the 4.9-rc6 (Release Candidate) Linux kernel, noting that “things have stayed pretty calm” but that enough outstanding issues remain that this may be one of those development cycles in which a rare RC8 exists (as opposed to the usual RC7 before final). In his mail, Linus shared that “nothing particular is bothering me all that much, but we’ve had some of the VMALLOC_ STACK fixups continue to trickle in”. We covered the virtually allocated kernel stacks feature previously. While a great development technically, VMALLOC_ STACK breaks occasional code that had (broken) bad assumptions. Most recently, a fix in GFS2 (a filesystem for clusters) was identified due to sharing of objects on separate kernel thread stacks no longer working. All this means that there may be some fallout,…

The single most important file related to file systems is /etc/fstab, which holds their mount points, their types and various other permissions about them – it is the job of the system administrator to alter and maintain the /etc/fstab file in order to contain the correct information. This file is used by the mount command to automatically mount the desired partitions when a Linux system boots. Two main kinds of partitions exist: data partitions and swap partitions. The main reason for creating multiple partitions is grouping similar data and separating data from system files and swap space. “When you want to document the characteristics and the role of a Linux system, you should start by learning about the partitions of its hard disks” Generally speaking, when you want to document…

Read Having read permissions on a file means that you can access its contents. The read permission on a directory gives you the ability to read the names of files in the directory. However, you can’t find out more information about the files – you will need the execute permission for this! If you try to access a file without having read permissions, even if you are the owner of the file, you will get the following kind of error message: Write Having write permissions on a file means that you can alter or delete the file. Having write permissions on a directory means that you can create new files, rename existing ones or delete files from it. However, if the execute bit is not set, you will not be…

Resources OWASP 2013-Top 10 bit.ly/1a3Ytvg WebSecurity Dojo Installation bit.ly/2fvdkfx OWASP ModSecurity Core Rule Set bit.ly/1EKRPik sqlmap bit.ly/2fv8dvY Android X86 Installation bit.ly/2eflsRF JD-GUI http://jd.benow.ca/ Dex2Jar bit.ly/2fv8wGW A1-Injection is the term by which the OWASP 2013 Top 10 awareness document identifies the first and most critical risk that any organisation must face when it comes to information security. SQL injection (SQLi) falls into this category. This sort of injection is relatively easy to spot and exploit; there are myriads of websites affected by it. Although this issue is commonly found in web applications, Android apps and other operating systems, applications can be vulnerable to SQLi as well. SQLi attacks can be divided into three main categories: in-band, inferential and out-of-band. Whereas the first two both use the same channel to perform the…

Resources tmux tmux.github.io Traditionally, a shell instance is spawned when a user logs in.If their session gets lost – for example, when an SSH connection dies – the shell and all programs contained within also disappear. Tmux – the name stands for terminal multiplexer – takes a different approach. It comes in the form of a long-lasting process, which acts as a host to one or more shell instances and the programs contained inside of them. This is interesting for a variety of reasons: first of all, a breakdown of the SSH connection (hello, unreliable internet connection!) is no longer a disaster, as tasks running in tmux keep running. This is helpful when compiling Qt or doing other long-running jobs: the command workstation does not need to keep running. The…

“Maui is one of the few distributions where Steam really works without fault” Maui Linux Linux doesn’t have a reputation for being one of the better operating systems to fulfil our entertainment needs. Misconceptions of poor designs, awkward code and boring programs are all commonplace for those looking into the world of Linux, but little do they know that there’s a growing number of entertainment-based distributions that are perfect for all you film and audio enthusiasts out there. Despite plenty to choose from, we reckon that Maui is the best one for users to download in 2017. Various elements of the distribution have been tailored with those seeking their entertainment fix in mind. A native version of the VLC Media Player is readily included, and has been heavily optimised for…

“The Parrot team has managed to implement a virtual lab that can be used to do forensic acquisitions” Parrot Security OS When it comes to choosing your next Linux distribution, arguably the most crucial deciding factor is how secure it is. People want a distro that’s able to identify vulnerabilities in their desktop, eradicate them and equip them with tools to protect them down the line. You’ll be surprised with how few Linux distributions actually do this, but the ones that do are generally fantastic. One of the best is Parrot OS, a security focused distribution designed with cloud pen testing and IoT security in mind. We won’t lie and say this is one of the more user-friendly distros out there; in fact, it’s for those who really take their…

What you’ll need • Raspberry Pi • Pimoroni Enviro pHAT Pimoroni makes a wide range of HAT (Hardware Attached on Top) boards for the Raspberry Pi. These boards are designed to be fully compatible with all Raspberry Pi models. Enter the Pi Zero, a super-slim, super-cheap, $4 version of the Pi. In response, Pimoroni created a range of HATs that fit the Pi Zero, called pHATs. This tutorial focuses on the Enviro pHAT, a nifty little board that packs in four different sensors that let you measure temperature, pressure, light levels, colour, acceleration, take a compass heading and retrieve readings from analog inputs. This creates up to ten different variables, making it ideal for monitoring conditions in your house, garage or garden. This tutorial will walk you through the initial…

RAM 128MB RAM Storage 10GB HD Specs 1GHz processor 32 and 64-bit As far as Ubuntu-based distributions go, Bodhi Linux has maintained its reputation for being one of the most improved in the past 24 months. Its most recent 4.0 update has been in the alpha phase for just over three months, but that has proved to be a wise decision, with the final product improving Bodhi in a number of areas. Installation has always been a relatively easy affair with Bodhi, and despite some initial download issues, the entire process is relatively problem-free. Download files are a little smaller compared to most Ubuntu updates, which is handy if you don’t have access to a strong internet connection. One potential worry is that there’s no direct upgrade path available from…

Welcome to the Linux User & Developer DVD. This issue, we’re looking ahead to the next year in Linux, so we’ve selected the best distros and FOSS for 2017. Give some of them a whirl now – you’ll find Puppy Linux, Maui and Arch Linux to live boot from this disc, while our other picks join the Distro Directory. Remember, you can get all of the FOSS in our feature straight through your distro of choice, or from their respective websites. Featured software: Puppy Linux Puppy Linux is a special build of Linux meant to make computing easy and fast, even allowing you to do magic by recovering data from destroyed PCs or by removing malware from Windows. It’s our pick for the best lightweight distro, as it’s so small…

Depending on your distribution of choice, some of you will have heard of the Trinity Desktop Environment, and some will not. Known for its design and simplicity, Trinity can be found on the likes of SparkyLinux, PCLinuxOS and CentOS to name but a few. Its latest 14.0.4 release comes after over six months of development. “R14.0.4 is the fourth maintenance release of the R14.0 series, and is built on and improves the previous R14.0.3 version. Maintenance releases are intended to promptly bring bug fixes to users, while preserving overall stability through the avoidance of both new features and major codebase re-factoring,” reads the official release statement. “Known for its design and simplicity, Trinity can be found on the likes of SparkyLinux, PCLinuxOS and CentOS” While by and large this is…

Top 10 This month Stable releases (10) In development (7) While many of the big players have been struggling this month, the lesser known Antergos has started gaining some traction. Can it gather momentum and climb the ranking? Highlights Antergos Despite releases being few and far between, Antergos continues to build its user base thanks to its modern and elegant take on Arch Linux. It utilises the Cinnamon desktop well, but can also be customised to run Xfce, GNOME 3 and Razor-qt. openSUSE The final release candidate of openSUSE 42.2 has just arrived, and with it, a whole host of new options. Better video functionality and overall desktop speed are the big improvements here. Manjaro Linux Another distro based on Arch that’s making waves in the top downloads…

Becoming a system administrator is a process, rather than a decision that you take at a given time, because it requires knowing many things that take time to learn well. Most administrators start by administering their own Linux server before becoming good at it and gaining a professional role. Here, we’ll talk about the five most important tasks that an administrator needs to learn, and mention other useful skills that, if you acquire them, will take you to the next level. In order to become a Linux system administrator, you will need to learn many skills, techniques and technologies along the way. However, nothing can replace practice, reading books, asking questions and observing the way experienced system administrators work. Being successful in system administration requires many skills, including a good…

1 Directories Directories are entries on a file system that contain lists of other files and directories. This happens with the help of inodes, which are data structures that hold information about files and directories. Figure 2 (next page) shows the use of inodes for connecting directories with files. You can get useful information, including the inode number, about a directory or a file using the stat command. 2 Special files You might already know that UNIX accesses everything as if it was a file – this includes printers, keyboards, hard disks and so on. As a result, not every file on a Linux machine is a regular file. In order to make things simpler, Linux puts most of its special files inside the /dev directory and its subdirectories, as…

As most of you already know, security is important! The list of security tools and techniques that you see later on is just a good starting point. What the list does not mention is the value of log files. Log files are text files that can be easily searched using tools such as grep and AWK in order to extract the kind of information you want. The following two commands extract security information from the Apache access log files of a Drupal site and a WordPress site, respectively: Both commands display hacking attempts per hour. For the WordPress site, you want to monitor the "POST /wp-login.php HTTP/1.1", “POST /wp-login.php HTTP/1.0”, "GET /wplogin.php HTTP/1.1" and "GET /wp-login.phpHTTP/1.0" requests that indicate brute force hack attempts. For the Drupal site, you want to…

Define the problem The most important phase of the optimising process is defining the problem you want to solve. In other words, you should make sure which part of your Linux system runs too slowly before trying to make things faster, or you may try to solve the wrong problem! Put simply, if you are running only two Apache server processes in order to serve 1,000 users, then using a faster network card will not help as much as starting more Apache processes! As Linux systems and networks are fairly complex, there are many things that can run too slowly – designing well-defined and easy-to-understand solutions will definitely help you during optimisation. Identify bottlenecks When you are sure about the problem you are trying to solve, you should attempt to…

Although all the aforementioned topics are essential for every system administrator, having some additional skills is also desirable as this might differentiate you from other administrators. This section will mention some of them, including some specific tools that you will need to learn to make your life easier. However, the single most desired skill for a system administrator is programming using a scripting language such as Perl, Python or Ruby. “The single most desired skill for a system administrator is programming using a scripting language such as Perl, Python or Ruby” So, you might ask, “Do I need to know just one programming language, or more of them?” The safe answer to that question is that you should learn one of them very well and know how to do basic…

Resources Linux or OSX machine with internet access Python 2.7.x and pip installed on the local path Git 1.9.3+ A free SourceClear.com account https://www.sourceclear.com/ The average software project today relies on dozens – sometimes hundreds – of open source libraries. Are those libraries up to date? Are there any security vulnerabilities in the versions you’re using? How would you even know? SourceClear makes it easy to answer these questions and more, automatically. You’ll get complete analysis of your open-source dependencies – security vulnerabilities, out-of-date libraries, and license reports. To analyse your project, we’ll be using the SourceClear command-line agent. By tapping into the native build and package managers that manage open-source dependencies, we’ll start by gathering information on the full dependency graph. We’ll then match up those libraries to the…

“Since its re-emergence on the market, the entire distribution has changed” Solus Linux has never been well regarded as the operating system of choice for everyday users. Those looking for a system that they can use to browse the web, watch videos and play a few games will often lean across to Windows. However, there’s a growing market of distributions looking to entice these everyday users. While they don’t perhaps offer the technical side of things that Linux is renowned for, they do offer a convenient and usually simple experience for their users. One of the best to emerge in 2016 was Solus, a rebranded project that originally debuted back in 2011 but was soon abandoned. Since its reemergence on the market, the entire distribution has changed. At its core…

“It acts as a toolkit, giving users everything for building their own custom version of Linux” Arch Linux The most hotly contested area of the Linux ‘distroverse’ centres on development. Or more importantly, which distribution gives its users the best platform and tools for their projects? Hundreds of emerging distributions have all looked to establish themselves as the premier development distribution, but very few have withstood the test of time. Arch Linux is one of the oldest distributions out there, but has undergone regular updates to continuously bring its users the latest tools, features and fixes for their desktop. It’s a developer’s dream distro throughout. Essentially it acts as a toolkit, giving its users everything they need for building their own custom version of Linux that works for them. It…

“Tails doesn’t save anything on your desktop’s hard disk, instead storing it on your available RAM” Tails It seems like every week that we’re hearing about a new potential exploit, deadly malware or sophisticated hack that can somehow damage our desktops. Never before has a user’s privacy been more important, and many of us are looking for a distribution that can aid us in this cause. One of the best that’s promising big things in the coming months is Tails. Not only is it the distro of choice for whistle-blower Edward Snowden, seriously, it’s undergone a massive transformation to make it our favourite secure distribution. Its core aim is to provide security through anonymity, using the Tor network to route any and all internet traffic. Due to this network protection,…

What you’ll need • This tutorial is compatible with all models of Pi running Raspbian Jessie With the advent of the dazzling Pixel desktop on the Pi, with its glitzy icons and crisp windows, some readers may be considering using a Pi as their home computer. This however is not especially secure given that the Pi automatically logs in the default user without requiring a password. Even if the password is required, anyone can mount the SD card to view your documents, pictures, videos and other data. 01 Back up your data If you have not done so already, log onto your Pi and transfer the contents of your Desktop, Documents, Pictures etc onto an external medium like a USB stick. This will make transferring your data to your encrypted…

"You can have your Pi actually driving some kind of GUI" “Most of the articles in this column have looked at various methods you can use within your own Python programs. This way, you can create rather sophisticated projects centred on the Raspberry Pi. Most of these have assumed that your Pi will either be running headless (that is, with no display device), or only running with a text-based display. This time we will look at how we can add graphical display elements to your Python program. This way, you can have your Pi actually driving some kind of GUI for your project. There are several graphical frameworks available to add GUI elements to your code. We will be specifically looking at Kivy. It is a cross-platform graphical framework that…

Specialist bootable Linux distros have been around for so long that we take former favourites for granted, and perhaps forget to see what else is out there, quietly doing the job better than whatever we’re currently using. In the crowded field of ‘lightweight yet useful’, TheSSS stands out with its well-chosen collection of server software and easy command line interface, as well as frequent updates, thanks to being based on the (rather less than lightweight) 4MLinux. That server software includes FTP, HTTP, SFTP, SSH, Telnet, Polipo proxy server with Tor anonymiser, 4MLinux’s iptables Firewall, and Clam AntiVirus. The latter will scan all of the disks of the machine that you boot it on, and give you various options over what to do with suspicious files, as well as letting you…

“A state-of-the-art data centre environment enables Netcetera to offer your business enterprise-level colocation and hosted solutions” Featured host:   www.netcetera.co.uk 0800 808 5450 About us Formed in 1996, Netcetera is one of Europe’s leading web hosting service providers, with customers in over 75 countries worldwide. As the premier provider of datacentre colocation, cloud hosting, dedicated servers and managed web hosting services in the UK, Netcetera offers an array of services designed to more effectively manage IT infrastructures. A state-of-the-art data centre environment enables Netcetera to offer your business enterprise-level colocation and hosted solutions. Providing an unmatched value for your budget is the driving force behind our customer and managed infrastructure services. From single server to fully customised data centre suites, we focus on the IT solutions you need. What…

Live boot Insert the disc into your computer and reboot. You will need to make sure that your computer is set up to boot from disc FOSS Free and open-source software needs to be installed via the distros or by using the disc interface Distros Distros can be live booted so that you can try a new operating system instantly without making permanent changes to your computer Explore Alternatively you can insert and run the disc to explore the interface and content Important information Check this before installing or using the disc For the purpose of this disclaimer statement the phrase ‘this disc’ refers to all software and resources supplied on the disc as well as the physical disc itself. You must agree to the following terms and conditions before…

1 Antergos Although it started life solely offering the Cinnamon desktop, Antergos has carved a name out for itself by being one of the few Arch-based distros that now offers support for GNOME 3, Razer-qt and Xfce. Without doubt its premier feature is that it provides its own graphical installation program. 2 Chakra While Chakra may not be as well-known as others listed here, it certainly trumps many in terms of usability. Automatic hardware detection is a big plus here, allowing for seamless integration for most third-part hardware on any desktop. 3 Manjaro Manjaro is one of the few Arch-based distributions to offer rolling release updates, but this method has helped its users receive timely and systematic upgrades. These improvements have led it to be one of the more popular…

One of the primary reasons Ubuntu remains one of the more popular distros of choice is the sheer number of unique ‘flavours’ it’s available in. While the likes of KDE, GNOME and MATE have helped develop Ubuntu’s user base further than ever before, a team of developers has now released the official Ubuntu Budgie flavour. In its current state, this release is said to be working on Ubuntu 17.04, and as of yet, it’s unknown how it’ll be supported and developed in years to come. Budgie is a desktop environment previously developed by the makers of Solus and incorporates many of the core GNOME features, but includes its own unique user interface. In Ubuntu Budgie, users will have access to the complete suite of Budgie features, which include the Raven…

“For our readers who may not have heard of the evive toolkit, could you give us an overview of what it is and what it does? evive is an Arduino-based open-source platform for learning and prototyping electronics circuits, creating robots and hacking together IoT solutions. It has been designed as a one-stop solution for the student, hobbyist and maker communities. The idea behind evive was to make prototyping completely intuitive and user-friendly, and we have done just that with our menu-based visual interface, which removes the need to reprogram the Arduino frequently and removes repetitiveness. evive offers highly accurate sensing capabilities for IoT applications and debugging, all in a portable battery-powered unit. evive has successfully completed a crowdfunding campaign on Indiegogo, raising $34k from 300+ backers in over 30 countries.…

1 Manage file systems The management of file systems is a very crucial task because the way you define your file systems, including their size and their type, cannot be easily changed afterwards. However, techniques exist, including backup and restore procedures, which can help you resize a file system in a reliable way. The most crucial partition is the root, which is the first one to be mounted, and contains all the necessary files for a Linux system to boot, including the Linux kernel. 2 Manage and support users Linux machines support multiple users and groups of users. Each user belongs to at least one group, which is their main group, but can also be included in other groups. You can find the groups of a user with the help…

nmap One of the first tools you should install and learn is nmap, which is a port scanner. Figure 6 shows the output from an nmap port scan using an ADSL router as its target. As nmap uses the external IP address of the router, this also shows you what a potential hacker would see. Bear in mind that scanning the same ADSL router from the internal network using its internal IP address gives you a different output. lsof The lsof utility lists open files – as everything on a Linux machine is a file, this includes almost everything! The main advantage of lsof is that it gives you detailed information about the processes and the open ports of your Linux machine. However, you will need to have SSH access…

Troubleshooting gives you the opportunity to use everything that you have learned about system administration and combine it with the other knowledge you have in order to solve a problem that arises, because the root of a problem can be anything from a damaged network cable to a hacker who has gained access to one of your servers! In other words, when troubleshooting you should assume that everything is possible! Troubleshooting is the single most vital task of a system administrator. When things go bad you should act quickly, accurately and efficiently. Put simply, you should discover the problem before your users or your boss, and try to solve as quickly as possible! Troubleshooting is also very exciting; nothing can beat the feeling of success that you will have after…

Resources Bash gnu.org/software/bash/bash.html Making the transition from traditional/interactive to unattended shell script execution requires a significant change of mindset: a shell script that gets invoked by the operating system must, by definition, run unattended and cannot take any kind of input from the user. In addition to that, debugging the script is difficult, as its output will often get redirected to invisible places. Working around this problem is best accomplished by using the syslog. It is a global event storage system that can be fed with information by various processes as they run. When this is implemented correctly, the developer of an unattended shell script can limit themselves to emitting the correct commands to trigger program execution. Checking the result is then just a question of checking the contents of…

Resources An installation of Erlang A text editor such as Emacs or vi This tutorial will be the first one in a series of tutorials about the Erlang programming language. Erlang is a functional programming language with many unique and interesting characteristics, and was developed at Ericsson in order to serve the switching of telephone equipment. Although it may look like a special-purpose programming language, it is not. Erlang can do many things, but it's most appropriate for developing highly available server processes. In other words, it's better to develop the server side of an application using Erlang than the client side. The purpose of this tutorial is to present you with a quick overview of how Erlang does things by giving you small yet complete code examples. The rest…

“You’ll be hard pressed to find hardware that Puppy won’t instantly detect” Puppy Linux Unless you’ve got the funds to back it up, chances are you’ll be running hardware that has a limit to the type of distribution it can handle. There are numerous power-hungry distros that come highly recommended, but many can cripple everything but the most high-end of desktops. For ageing machines in particular, sourcing a CPU-friendly distribution is of the utmost importance, but you want one that doesn’t skimp on core features and usability. Puppy Linux has garnered a reputation for being a low-resource distribution that still manages to cram a lot into its tiny frame. Its distinguishing feature is that it takes up just a paltry 100MB of hard disk space, and when mixed in with…

“Despite increased competition of late, ClearOS remains at the top of the enterprise pyramid” ClearOS Enterprise There has never been a better time to take your business into the world of Linux. Migration to the platform has never been easier, development tools have matured considerably and cloud tools are expanding at an alarming rate. The real problem lies with choosing the OS that can really be used to take your business to the next level, and trust us: there are a lot of options out there for business owners. Despite increased competition of late, ClearOS remains at the top of the enterprise pyramid, providing company owners with the tools needed to help bring their business into the digital age. Part of its appeal is its import package, providing the necessary…

“It’s very much an out-of-the-box experience, giving users all the tools they could need” Apricity OS Apricity is one of the few recently launched distributions that has opted for a rolling release, catering for those who like their distro updates arriving thick and fast. One of the most appealing features within Apricity’s arsenal is that it caters largely to the cloud generation of computing. At its core is the ICE browser manager, which provides users with all the tools needed to import their favourite web apps onto their desktop. It’s a feature that most distro repositories fail to implement, but the Apricity team has made it one of the staple features to increase its user base. Away from the ICE manager, it should also be noted that Apricity is based…

What you’ll need • Raspberry Pi • Four jumper jerky wires (female to female) • Design Spark tilt switch A tilt switch is a component capable of sensing a change in orientation in four different directions: up, down, left and right. The tilt switch from Design Spark makes it easy to incorporate this sensor into your projects by breaking the necessary pins out to standard 0.1” spaced headers. The board works at either 3.3 or 5 volts making it perfect for use with a Raspberry Pi. You can use it to orientate a robot, checking to see if it has fallen over, or how about embedding it within a box to check that it is facing the correct way up? Although not originally designed for the Raspberry Pi, this tutorial…

While this article covers Kivy as one possible framework for building GUI applications in Python, it isn't the only option available. The Python wiki site maintains a partial list of the frameworks available, at https://wiki.python.org/moin/GuiProgramming. If you want to have code that is portable from the Raspberry Pi to other platforms, you could use a multiplatform framework such as wxPython. This framework is built on top of the C++ framework, wxWidgets. On Raspbian, you can install it with this command: As with most frameworks, you need to create the tree of widgets for the user interface, and then execute some kind of run or loop method to activate the user interface. A Hello World application would look like: Another, simpler, framework that is commonly used is that provided by pygame.…

We’re sure you’re doing testing of all descriptions for your software – or at least have a good reason not to be – but what about your nice, responsive website design? Galen Framework gives you layout and functional testing, and automates much of the tedium of checking that your site does what it should on the myriad screen sizes that it’s likely to encounter. Written in Java and using Selenium and your default browser for tests, installation is easy, as a shell script unpacks Galen into /opt and creates a symlink from /usr/bin/local. You could just run the .jar without installing, if you’d prefer. The real work is configuring for your project. Typically, users will want different tests for each project, so: is run in the project directory, generating a…