Everyone has a favorite development platform. These registered port addresses can be seen in /etc/services. Another important feature of Linux is that it can run on a variety of different computer hardware platforms frequently found in different companies. The POSIX standard was born in 1988, as well as other …

Aliases are expanded when a command is read, not when it is executed. Commands run as a result of command substitu- tion ignore the keyboard-generated job control signals SIGTTIN, SIGTTOU, and SIGTSTP. People who are completely new to open source software often wonder how a group of random people can …

The other is part of OpenOffice, a full-fledged office productivity suite that is comparable to and compatible with Microsoft Office. Oracle Corporation, another heavyweight in the DBMS industry, recently announced it would be creating a Linux compatible Oracle. Likewise, some minimal restrictions are necessary for free software, namely the GPL …

In general, there is a tendency for advocates of the term term free software to emphasize the ideological aspects of software, including the ethical or moral aspects, and they view technical excellence as both a desirable and an unavoidable by-product of their ethical standards. The shell learns immediately whenever a …

For some small business leaders I've consulted, the human factor is either a notion to be rejected or ignored. For most users, LILO works best. Kerneld is just an agent of the kernel, scheduling work on its behalf. Not often are our basic rights thought of in the context of …

This, in turn, allows for the use of the pathnames with which all Unix users are familiar-for example, /home/blackbeard/concorde.png. Figure 5.1 shows that each file data structure contains pointers to different file operation routine vectors; one for writing to the pipe, the other for reading from …

Time enough for a soapbox. It could be argued that its smaller number of vulnerabilities is because of its rarer deployment, but the simplest explanation is that OpenBSD has focused strongly on security - and achieved it better than the rest. The BSD socket layer calls the INET layer socket support …

Now synonymous with private cloud computing, the OpenStack cloud framework likely would not exist, or at least would be incredibly different, without Linux. According to the Stack Overflow 2016 survey, desktop developers now constitute just 6.9 percent of all developers (and that also includes Mac Desktops). Without Linux as …

Othertimes, simply booting the machine can be a chore. The entire Linux kernel was written from scratch, without employing any code from proprietary sources. A process that has terminated, but has not yet been waited upon, is called a zombie. Linux allows you to include device drivers at kernel build …

Whenever a VFS inode representing a character special file is created, its file operations are set to the default character device operations . For this reason, it is referred to as Open Source Software (OSS). Rather than having to satisfy a set of needs laid out by a single department head …

Installation can take a while, depending on the speed of the computer and the options selected. Apart from the ability of a loaded module to crash the operating system by being badly written, it presents another danger. Each approach has its advantages and disadvantages. If your memory is like mine …

If it does not exist, it will allocate a physical page and create a page table entry for it. This means that, when the next module is loaded, it has access to the services of the already loaded modules. The shell executes the specified interpreter on operating systems that do …

Developing the core is pretty serious business, involving pretty serious computer science. But the existence and popularity of the Windows Subsystem for Linux (WSL), as well as more recently announced capabilities like the Windows port of Docker, including LCOW (Linux containers on Windows) support, are evidence of the impact that …

As the writing process writes to the pipe, bytes are copied into the shared data page and when the reading process reads from the pipe, bytes are copied from the shared data page. To make it easy to find, the current, running, process is pointed to by the current pointer …

This is used by gateways, which respond to ARP requests on behalf of IP addresses that are in the remote network. Many, if not most, PCI modems available on store shelves these days are WinModems. This means that subsequent INET socket calls can easily retrieve the sock data structure. Figure …

The Linux kernel, supporting both preemptive multitasking and virtual memory, provides every process both a virtualized processor and a virtualized view of memory. This is true even if the device is a modem being used by the PPP daemon to connect a Linux system onto a network. Therefore Linux adds …

Therefore, when moving to the PDP-11 as the main hardware platform, the developers started C as the as a core language for Unix. Advocates of copyleft respond by pointing out that there is no such thing as absolute freedom. The test and set operation is, so far as each process …

Its purpose is to provide a financial incentive for producing such works in order to benefit society as a whole. It also has a utility to let you select real-time kernels. The systemd-boot bootloader generates a menu of boot image options, and can load any EFI boot image. When a …

It also helps to know how to access the Internet and be able to do basic web searches with a search engine such as Yahoo or Google. Of course, we knew that all along. This means that subsequent INET socket calls can easily retrieve the sock data structure. For example …

The UEFI boot manager boots the mini-bootloader, then, in turn, it boots the standard Linux bootloader image. The exact wording of a recipe as it is written by its author is protected under copyright law, but the information itself (i.e., the names of the ingredients, their quantities and the …

Why make it easier for them. However, in most cases it is closed source (i.e., the source code is kept secret), and there are often restrictions on the use of the executable version. If all of the semaphore operations would have succeeded and the current process does not need …

In a multiprocessing system many processes are kept in memory at the same time. The kernel does not impose any restrictions on concurrent file access. This software universe had been going on behind my back for years. Just maybe that crash you reported will save some people from a major …

It will recognize a multiline header if the last character on each line but the last is a left parenthesis or comma. In general, failing to agree with the standards is considered a bug. So, be prepared. The key to success with studying at home is strong motivation.

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Interestingly, the ability of bash scripting is also one of the most compelling reasons why programmers prefer using Linux OS. Linux has two types of system timers, both queue routines to be called at some system time but they are slightly different in their implementations. Most open source Internet tools …

Of course, most system calls have only a couple of parameters. So now you are probably starting to see that we can refer to a location in a variety of different ways. The saved uid stores the original effective uid; its value is used in deciding what effective uid values …

Processes that are started at boot time usually run as root or nobody. As a Linux user today you have all the means of getting to know your system inside out, but it is no longer necessary to have that knowledge in order to make the system comply to your …

In this case, Direct Memory Access (DMA) controllers are used to allow hardware peripherals to directly access system memory but this access is under strict control and supervision of the CPU. This creates a new vm_area_struct data structure describing the shared memory for this process. The thrust behind Linux development …

Finally there is the main memory which relative to the external cache memory is very slow. Yes, it behaved slightly differently, but I found I could be much more efficient - while using Free Software! There are various other techniques how to define shell interpreter, but this is a solid start …

The IP protocol is a transport layer that is used by other protocols to carry their data. As the cliche goes, "If we both have an apple, and we exchange apples, we each still have one apple. It provides the interfaces documented in SUSv4 and POSIX 2008, including real-time (POSIX …

Where does the bash fit in? The keyboard, mouse and serial ports are controlled by a SuperIO chip, the IDE disks by an IDE controller, SCSI disks by a SCSI controller and so on. Linux is believed to comply with POSIX.1 and SUSv3, but as no official POSIX or …

Therefore, mastering Linux for configuring and maintaining servers is a must to have skill for any technological entrepreneur who operates end-to-end applications. The scalability and flexibility of Linux enable many of these massive deployments to actually work, while the significantly reduced cost barriers of Linux make them more financially feasible …

For kernel code, once it is complete the developer may ask Linus to include it in the standard kernel, or as an optional add-on feature to the kernel. An inode stores metadata associated with a file, such as its modification timestamp, owner, type, length, and the location of the file's …

It is vital that there is an uninterrupted stream of knowledge, and that information is not held back for personal benefit at the cost of others. Most of the time you will be issuing commands. Anyone can join the Linux community by participating in and contributing to this mailing list …

The Watergate scandal leaked to the press through one of US President Nixon's most trusted colleagues. Device drivers have to be careful when using DMA. By the time I was done, I had actually forgotten how to use my old piece of proprietary garbageware. Linux is open-source.

How much do …

Linux (as well as many other areas of information technology) is particularly well suited for studying at home because (1) no equipment is needed other than an ordinary personal computer and (2) there is a large amount of free or modestly priced study material that is available from bookstores, in …