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 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 various steps in their processing) is not. Even so, if a process executes until it waits then …

The read/write heads are moved across the surface of the platters by an actuator. The BSD socket layer passes the socket data structure representing the BSD socket to the INET layer in each of these operations. An operating system needs to be able to schedule an activity sometime in …

federal government. A pipe (its two file data structures, its VFS inode and the shared data page) is created in one go whereas a FIFO already exists and is opened and closed by its users. Another disadvantage of Open Source is the support service. If the expiry time for an …

Compare this to a floppy disk which only spins at 360 RPM. In fact, it seemed so obvious that the situation with regard to software resembled that of mathematics or recipes that terminology such as free software, freeware and open source software did not exist for many years. The terminal …

If the process has not blocked the signal and is waiting but interruptible (in state Interruptible) then it is woken up by changing its state to Running and making sure that it is in the run queue. In addition to implementing the standard C library, glibc provides wrappers for system …

Closed source software can be distributed for free or for a cost; either way, the source code for the software is unavailable from the original developers. In Linux, no further organization or formatting is specified for a file. Until Linux came along it was either Windows or Macintosh - take it …

The same good practices and understanding of the underlying system inform and benefit all forms of programming. That way you can still change the GRUB 2 bootloader image without having to worry about the digitally signed shim.efi file. Because your server will be probably Linux-based as well, it will …

The price for a Windows license amounts to an average of one fourth of each new computer's price. Many of the devices you own probably, such as Android phones, digital storage devices, personal video recorders, cameras, wearables, and more, also run Linux. Linux systems always have a root filesystem. Again …

It does not obligate you to run it on a determined platform like some proprietary software. However, this is definitely no loss. Its interface with the BSD socket layer is through the set of Internet address family socket operations which it registers with the BSD socket layer during network initialization …

Some applications are written exclusively to higher-level abstractions. This means that you cannot DMA directly into the virtual address space of a process. Whenever you refer to a file or directory on the command line you are actually referring to a path and your path can be constructed using any …

Different distributions have chosen varying approaches to file placement, software management, and other subtleties, in such a way that makes it almost impossible to make an applications distribution that will install and run cleanly across the Linux spectrum. For people wanting to become more than just casual users, it can …

The new vm_area_struct structure is put into the list of vm_area_struct pointed at by the shmid_ds. Internally, the quality assurance department runs rigorous regression test suites on each new pass of the operating system, and reports any bugs. It then restores the state of the new process (again this is …

The U-Boot bootloader program can boot from any type of disk, and load any type of boot image. Linux can do everything NT does, usually faster, definately more stable and at a fraction of the cost. Both have similar tools for interfacing with the systems, programming tools, filesystem layouts, and …

This means that if a system has two IDE controllers there will be entries for the IDE subsystem at indices at 3 and 22 in the blk_dev and blkdevs vectors. When someone detects a bug it reports it to the community and they release a patch as soon as possible …

It was coined in 1997 with the intention of replacing the term free software in order to avoid the negative connotations that are sometimes associated with the word free and thereby make it more attractive to corporations. Hard links do not incur this additional overhead-there is no difference between accessing …

How these modes are supported by the underlying hardware differs but generally there is a secure mechanism for getting from user mode into system mode and back again. Given that Linus was using several GNU tools (e.g., the GNU Compiler Collection, or GCC), the marriage of the GNU tools …

Every transmitted ethernet frame can be seen by all connected hosts and so every ethernet device has a unique address. The pops vector is indexed by the address family identifier, for example the Internet address family identifier (AF_INET is 2). If the thief runs, he/she probably won't get caught …

Whenever a process has to wait the operating system takes the CPU away from that process and gives it to another, more deserving process. The container is when the image is running, such as loading an ISO file in Virtualbox and installing it. Writing a byte to a file position …

But it starts at the top. In many ways, Linux and UNIX administration is today much easier than administration for popular commercial personal operating systems because it is much more transparent. It stands to affect the people of the world at least as profoundly as the Industrial Age. Multiprocessing is …

There are no set boundaries or any limitations. The visibility and easy access to the source code, which I mentioned earlier, can also be a double-edged sword as bad-intentioned people can find vulnerabilities and leave backdoors for future exploits. Processes begin life as executable object code, which is machine-runnable code …

It is time for the opening of the tools that will be needed to build this new age. The physical on-disk form of this mapping-for example, a simple table or a hash-is implemented and managed by the kernel code that supports a given filesystem. The reality is that not only …

Named pipes (often called FIFOs, short for "first in, first out") are an interprocess communication (IPC) mechanism that provides a communication channel over a file descriptor, accessed via a special file. I say somewhat, because the use of sed in conjunction with pipes is somewhat more comfortable (at least to …

Whereas pwd is just run by itself with no arguments, ls is a little more powerful. If this execution fails because the file is not in executable format, and the file is not a directory, it is assumed to be a shell script, a file containing shell commands. They are …

A keyboard is an example of a character device. Not only you earn more capabilities as a developer, you also learn (sometimes the hard way) how to solve issues, monitor your machine for potential problems, configure different components and more. However, free software itself is not. The takeover of software …

Internal commands are, as you might expect, built into the shell program. In contrast, the source code for closed source operating systems is not released to the public for scrutiny, which means customers must rely on the vendor of that closed source operating system to provide secu- rity. Frequent emails …

The job of cache coherency is done partially by the hardware and partially by the operating system. One side note is that the popularity of the macOS hardware and operating system as a platform for development that mainly targets Linux may be attributed to the BSD-like macOS operating system. There …

As you can see, long hand command line options begin with two dashes ( -- ) and short hand options begin with a single dash ( - ). Use man command to display manual page of any desired command. There are several good reasons for becoming familiar with Linux. Where do you think Microsoft gets its …

Proficiency with the proprietary Unixes has always been considered valuable, and it is well rewarded in the job market. The results of such concurrent accesses rely on the ordering of the individual operations, and are generally unpredictable. But I don't see the need for a true Linux Advocate to spotlight …

Linux systems always have a root filesystem. Linux does not. Signals have no inherent relative priorities. Even in the days before the Internet, information and so-called "intellectual property" could still be, and were, exchanged.

A simple guide to resize2fs

Each process consists of one or more threads of execution (usually …
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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 source. This means that it's not enough for a Linux platform to support what an enterprise needs right now. People who are completely new …

Although initially intimidating for many inexperienced users, using an all-text mode, also referred to as a command line interface (CLI) or a shell, can provide valuable experience for those who want to become truly proficient at Linux. Even so, most software developers, even those who have grown up during this …

Now Linux must check that any waiting, suspended, processes may now apply their semaphore operations. Much of enterprise IT's excitement is focused on advancements at the application level (and rightly so), but it's Linux that powers these innovations and helps to drive modern computing forward. If you're interested in writing …

The device identifier for the first partition of that disk (/dev/hdb1) is (3,65). Shell scripting is really what separates novice Linux consumers from advanced Linux users. This is why our previous shell script works even without us defining bash as an interpreter. The inode contains metadata associated with …