The inode is both a physical object, located on disk in Unix-style filesystems, and a conceptual entity, represented by a data structure in the Linux kernel. It may not be the best choice for word processing (or maybe it is -- read on), but many see it as an "ISP in …

The four bytes are written as four decimal numbers in the 0-255 range, separated by dots. In this case the waiting process will be suspended and another, more deserving process will be chosen to run. The most difficult part of the installation process is, without a doubt, partitioning the hard …

Newbies can directly cat crontab file to see the syntax in case they forget it. The API merely defines the interface; the piece of software that actually provides the API is known as the implementation of the API. There are editors, compilers and interpreters for nearly every language ever created …

This means that when the next process that attempts to access this memory gets a page fault, the shared memory fault handling code will use this newly created physical page for that process too. Many Unix systems (such as Solaris) scale well to specific large platforms, but not as well …

For example, you cannot unload the VFAT module if you have one or more VFAT file systems mounted. In fact, there is no difference between command execution directly via terminal or within a shell script apart from the fact that the shell script offers non-interactive execution of multiple commands as …

This modest computer's official Raspbian OS comes loaded with tons of programming tools, connector pins, and other useful ports. To accomplish more complex tasks, tools would simply be connected together, using pipes. For self study it can be useful to have a good introductory book. Organizations today do not need …

A server is a computer with an operating system that is configured to allow other computers to connect to it from across a network. Keep in mind that these are only conventions---not rules. Setting up TCP/IP connections is very different from setting up an amateur radio X.25 connection …

You need to start from the ground up, choose components, and build a customized operating system that could easily become a great Linux distro for programming and other development purposes. Each filesystem is mounted to a specific location in the namespace, known as a mount point. One who bases his …

An exit status of zero indicates success. One year after the disclosure of Meltdown and Spectre, it is increasingly clear that we are dealing with an entirely new class of problems that will be keeping us busy for some time yet. A CPU is a small but powerful semiconductor device …

The platters are attached to a central spindle and spin at a constant speed that can vary between 3000 and 10,000 RPM depending on the model. These applications are not going away anytime soon. When there are no more characters left to read, the device returns end-of-file (EOF). The …

The name is an acronym for the 'Bourne-Again SHell'. Track 0 is the outermost track and the highest numbered track is the track closest to the central spindle. If no output_file is supplied, output goes to stdout. The maximum file length, as with the maximum file position, is bounded only …

To help bring order to chaos, standards groups codify system interfaces into official standards. Many of the best Linux experts are self taught and do not possess a single computer certification. It needs to be able to support what an IT team requires in the moment and in the future …

Like the virtual filesystem, Linux abstracts the socket interface with the BSD socket layer being concerned with the BSD socket interface to the application programs which is in turn supported by independent address family specific software. This is especially important if a particularly vital application does not yet exist for …

True, they are often needed for one project or another and can be well worth the cost, but for a beginner or a learner -- and for many professionals -- free software is simply irreplaceable. It also sets up the file data structure describing this character special file, making its file operations …

The API user (generally, the higher-level software) has zero input into the API and its implementation. The file position starts at zero; it cannot be negative. Processes are generally associated with a user's login group, not any of the supplemental groups. (Even of the large corporately-funded developer base, many have …

There are many ways to make money, so why choose a method that requires investing just as much time and effort into making software that lots of people want to use as trying to prevent the usage of said software? Most shells offer a similar set of internal commands, but …

Mostly Linux kernel modules are device drivers, pseudo-device drivers such as network drivers, or file-systems. The IP protocol layer itself uses many different physical media to transport IP packets to other IP hosts. Software and other creative works enter the public domain only if the author deliberately surrenders the copyright …

The basics of Unix programming have existed untouched for decades. So, if the operation value is 2, then -2 is added to the adjustment entry for this semaphore. Linux provides kernel memory allocation and deallocation routines and it is these that the device drivers use. Relative to the on-CPU cache …

This hides the underlying differences from the generic system calls which read and write to ordinary files. It was a failure. When it boots, it automati- cally looks for a GRUB 2 bootloader image file named grubx64.efi, also in the uefi folder on the system. Windows 10 is perhaps …

Although directories are treated like normal files, the kernel does not allow them to be opened and manipulated like regular files. Any ethernet frame transmitted to that address will be received by the addressed host but ignored by all the other hosts connected to the network. Some operating systems, such …

It will even automatically look for requests for missing or non-existent web pages, known as 404s. Most of the servers that hold the entire internet are Linux-based for many reasons that will not be listed here. The access file logs every visit to your web site. The shell program is …

This integration would result in efficient administration. Filesystems usually exist physically (i.e., are stored on disk), although Linux also supports virtual filesystems that exist only in memory, and network filesystems that exist on machines across the network. Most processes consist of only a single thread; they are called single-threaded …

Absolute paths specify a location (file or directory) in relation to the root directory. A 100Mhz processor will receive 100,000,000 clock ticks every second. Background processes that attempt to read from (write to) the terminal are sent a SIGTTIN (SIGTTOU) signal by the terminal driver, which, unless caught …

They will not begin with a slash. In general, failing to agree with the standards is considered a bug. Not all four entries in the partition table have to be used. None other than the system call handler!

Scan the results of parameter expansion

At that time a new generation of computers with proprietary operating systems was introduced, and their vendors required that users sign non-disclosure statements in order to obtain copies of the operating systems. Software running on the CPU must be able to read and write those controlling registers. (To be a …

For example, the term open source is of much more recent origin. Device drivers have to be careful when using memory. Those licenses must adhere to the open source definition but might contain extra conditions that the open source defini- tion does not. It is interruptible, so it can receive …

As a result of this restriction, artistic licenses are rarely used because many developers do not want to work on potentially futile projects. So, you can focus on the development work and leave other worries aside. The CPU can access both the system space memory and the I/O space …

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 …

The text section contains executable code and read-only data, such as constant variables, and is typically marked read-only and executable. At the same time, many executives have a crude interpretation of its value to corporations?"It's free, and therefore it's cheap." Slowly, that mentality is changing, but it's still true …

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 …

That is, there are no legal restrictions on anyone using, studying, copying, modifying, improving or publishing any recipe. Luckily, basic maintenance and basic security are pretty easy. One of the best parts about Gentoo, which is also a curse for some people, is its ability to configure what compilation flags …

The API merely defines the interface; the piece of software that actually provides the API is known as the implementation of the API. Finally, when the connection is no longer needed it can be shutdown. Once connection has been made, any of the (usually) several browsers available can be used …

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 …

However, this is definitely no loss. Big data, the collective term for the mountains of information produced by businesses, can hold the keys to more efficient operations and even increased revenues by identifying new opportunities, but first this data must be sorted, parsed and analyzed. As you can see, the …

For example to display a manual page for the ls command execute man ls. Linux must handle readers opening the FIFO before writers open it as well as readers reading before any writers have written to it. You may then continue typing and hit Tab again and it will again …

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 …

Microsoft was recently discovered to be using code stolen from a competitor on a social networking site, even though the code was never released. The Systemd-boot bootloader program is starting to gain popularity in Linux distribu- tions that use the systemd init method (see the next section). A process is …

Internally, the Linux kernel implements a unique view of threads: they are simply normal processes that happen to share some resources. The only rule is that when you develop something new out of the source code, you must share that code with everyone else. The init process routinely waits on …

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 …

Behavior changes and features are added. Aliases are expanded when the function definition is read, not when the function is executed, because a function definition is itself a compound command. As long as the system appears to be free of critical or oft-manifesting bugs, it is considered ``stable' and new …