The code is supplied on CDROMs or other media with the executable program and/or it is made available for downloading from the Internet. For example, software that can be freely modified but that does not have the same strict requirements for redistribution as the GPL is also considered open …

Moreover, even older and simpler machines can be used to study Linux without a graphical user interface (GUI), i.e., with only text and no images on the display screen. insmod copies the module into the allocated space and relocates it so that it will run from the kernel address …

Processes are free to use a FIFO so long as they have appropriate access rights to it. Most people believe it is wrong to steal, and therefore, won't rob a wallet. Today open source software has become critical for almost every organization. The access file logs every visit to your …

Device drivers have to be careful when using DMA. Let's face it; Windows OS is vulnerable to different types of attacks (or hacks). However, the root user is the only one who is able to add new users to the system. For self study it can be useful to have …

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 …

While early drones relied on proprietary operating systems, the boom in drone flight is helped onward by Linux, which provides the tiny embedded operating systems necessary to run many of these devices while allowing for more innovation on top of it. Businesses, educational institutions, governmental agencies and other organizations around …

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 …

When one single governing body gains absolute control over something, it is only a matter of time before that governing body increases its power tremendously. The application can then trap into the kernel through this well-defined mechanism and execute only code that the kernel allows it to execute. When the …

To accomplish more complex tasks, tools would simply be connected together, using pipes. As such it is possible to have two or more files and directories with the same name but letters of different case. The new vm_area_struct structure is put into the list of vm_area_struct pointed at by the …

For example, when we add a user named "paul," Linux creates a directory /home/paul. It is just the way Linux works that makes it a secure operating system. insmod copies the module into the allocated space and relocates it so that it will run from the kernel address that …

The LSB is a joint project of several Linux vendors under the auspices of the Linux Foundation (formerly the Free Standards Group). A filesystem is a collection of files and directories in a formal and valid hierarchy. Commercial programming packages, like commercial operating systems, can cost a great deal of …

Written originally for the Digital Equipment Corporation (DEC) family of PDP microcomputers, this most popular of multi-user, general-purpose operating systems has taken over roles in all areas of computing -- even those once held by mainframes. Although, there's no rocket science in it. Because of the rarity of malware threats, there …

The examples continue, but all hit the same chord: there is no use in preventing the spread of information. Well, you can't actually look at the four of them at the same time, but this doesn't matter since your eyes can't look in two directions at once, right? To help …

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 …

We have icons too, you know. An API defines the interfaces by which one piece of software communicates with another at the source level. These processes range from things like the X Window System to system programs (daemons) that are started when the computer boots. A runnable process is one …

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 …

The IDE disks are controlled by the IDE controller chip and the SCSI disks by the SCSI disk controller chips and so on. The Raspberry Pi, popular with hobbyists and enthusiasts, is Linux-driven and has opened the door for an entire spectrum of IoT devices running Linux. The timer bottom …

The fact that open source code offers complete transparency acts as an important guarantee of open standards. Constraining students to move the mouse within the confines of the instruction set of a few closed, proprietary programs merely cages those students and constrains our future. Unlike character devices, there are classes …

The following benefits are true about the Linux system:

Free dіstrіbutіons

One of the maіn features of thіs operatіng system іs the avaіlabіlіty of free dіstrіbutіons, such as Ubuntu, Mandrіva, Fedora, etc. All of them are quіte sіmіlar іn appearance and have one “phіlosophy”. Thіs fact іs very useful for …

Across the Internet and beyond, anyone with enough know-how has the opportunity to aid in developing and debugging the kernel, porting new software, writing documentation, or helping new users. Likewise, the smallest logically addressable unit on a filesystem is the block. Installation can take a while, depending on the speed …

The IP protocol is a transport layer that is used by other protocols to carry their data. One interesting feature it has is that every instruction is conditional. This collaboration among several developers with a common need speeds up software creation, and when bugs in the software are found by …

Some users have reported success configuring and installing drivers for the various winmodems, including Lucent, Conexant, and Rockwell chipsets. The application tells the kernel which system call to execute and with what parameters via machine registers. Each surface of the platter is divided into narrow, concentric circles called tracks. Another …

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 …

Institutions that rely solely on commercial-proprietary vendors - whether on-premises or cloud-based - effectively outsource their IT strategy and reduce their capability to deal with change with agility. This greatly assists integration efforts - and facilitates movement between systems when necessary. But, due to some recent changes, Ubuntu has switched back to GNOME …

All Unix versions and workalikes, including Linux, communciate between devices (computers, printers, cash registers, etc) using TCP/IP. Where Linux has shown a significant advantage over proprietary Unix is in its availability across a vast number of hardware platforms and devices. As both communities have matured over the past decade …

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 …

The IP protocol layer itself uses many different physical media to transport IP packets to other IP hosts. If you look at the output of lsmod, you will see that each module has a count associated with it. Until recently, most modems were 8 or 16 bit ISA cards. While …

The instructions executed by the processor are very simple; for example ``read the contents of memory at location X into register Y'. The target host that owns the IP address, responds with an ARP reply that contains its physical hardware address. Staff and students in the school have the tcsh …

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 …

Every device in the system is represented by a device special file, for example the first IDE disk in the system is represented by /dev/hda. But there may have a possibility of spreading malware to the Linux based systems if they are connected with Windows based systems. This is …

There are also numerous completely free resources available on the Internet, including (1) tutorials, (2) books and (3) newsgroups. This might seem a very unreliable method but every process in the system is making system calls, for example to write a character to the terminal, all of the time. In …

If a developer needs a VM or if IT Ops needs to provision a server, they expect to do so quickly and painlessly; Linux's scalability allows for this rapid provisioning, as does its lack of cost-prohibitive licensing. The Linux command line offers a wealth of power and opportunity. A good …

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 …

The major identifier for the primary IDE controller is 3 and is 22 for the secondary IDE controller. The GPL subsequently became by far the most widely used license for free software. The analogy is also frequently made with recipes for cooking food. Multiple processes are free to read from …

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 …

The numbers are different for an Alpha AXP Linux box. I am a composer, and one of the biggest hurdles for me in switching to exclusively Free Software was my sheet music typesetting software. The IDE subsystem registers IDE controllers and not disks with the Linux kernel. A common sector …

When a user-space application requests that a given filename be opened, the kernel opens the directory containing the filename and searches for the given name. If the expiry time for an active timer has expired (expiry time is less than the current system jiffies), its timer routine is called and …

The first, the old timer mechanism, has a static array of 32 pointers to timer_struct data structures and a mask of active timers, timer_active. Processes can choose to ignore most of the signals that are generated, with two notable exceptions: neither the SIGSTOP signal which causes a process to halt …