Questions tagged [operating-systems]

An operating system (OS) is a basic software whose rule is to intermediate software requisitions for resources and the hardware available, manage input/output, memory allocation/deallocation, file systems, among other basic tasks a device should do.

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Building a program that truly deletes everything

We all know that if we delete a file, the operating system is recycling it but doesn't actually delete it. It just removes it from the directory indexes, and until the data is needed and overwritten, ...
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Is ABI governed by hardware or is it only an agreement between software

ABI (Application binary interface) defines things like caller and callee saved registers, stack use, register use, end-of-routine stack pop etc. Is ABI only an agreement between compilers and other ...
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Sysadmin password storing

I'm quite unexperienced in the sysadmin area. Now I'm facing the responsability of managing two (remote) servers. I'm working in an informal organization. So I have passwords for the OS's users, ...
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1answer
118 views

What's contained in 'kernel mode' in virtual address space of a process?

I'm reading through Mickens' OS notes, and I came across the following depiction of a virtual address space. I conceptually understand "user mode" of a process' virtual address space. It ...
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2answers
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Can the operating system "break up" a memory allocation (Linux)?

Let's say a process (P1) is asking for 100 MB of memory, and the RAM looks like this: [[50 MB free] [USED] [60 MB free] [USED]] Since there are technically enough memory that are available (110MB ...
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1answer
98 views

Trying to understand OS-Level Virtualization

I'm trying to learn more about the fundamentals of containerization. I came across the term "OS-Level Virtualization" as the partitioning of the user space to further increase process ...
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9answers
707 views

Would we need Docker if applications were better behaved?

A well-written program will be configurable. It will have a configuration file or database which specifies where to look for files, which network ports to open etc. An Operating System lets many ...
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6answers
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Why is it called a "trap" instruction?

To execute a system call, a program must execute a special trap instruction. Why is it called a "trap" instruction? What is the etymology of this usage of the word "trap"? Is it ...
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1answer
433 views

Why does a condition variable's wait() release the associated mutex before blocking and reacquire it before returning?

Stallings' Operating System book says about condition variable in Solaris, A condition variable is used to wait until a particular condition is true. Condition variables must be used in ...
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224 views

Is a mutex lock always implemented as spin waiting?

Is a mutex lock always implemented as spin waiting? Can a mutex lock be implemented as block waiting? (Operating System Concepts section 5.4 only mentions the implementation by spin waiting. See below....
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1answer
437 views

Is there still busy waiting in the process-blocking implementation of a semaphore?

Operating System Concepts discusses two implementations of a semaphore, by busy waiting in Section 5.5 and by blocking the current process in Section 5.6: Section 5.5 A semaphore S is an integer ...
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1answer
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Who perform deadlock prevention, avoidance and check and recovery?

In OS books (e.g. Operating System Concepts), there are three strategies of dealing with deadlock between processes or threads: prevent, avoid, and check and recovery. Who performs the strategies? ...
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1answer
243 views

Does a safe state not lead to a starvation state?

In Operating System Concepts: 7.5.1 Safe State A state is safe if the system can allocate resources to each process (up to its maximum) in some order and still avoid a deadlock. More formally, a ...
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1answer
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Is there any reason I shouldn't use a LInux host for a Linux guest VM?

I'm a developer and my typical environment is to use is a Linux guest OS running inside VirtualBox on a Windows host. Most software companies don't allow developers to install Linux bare metal on ...
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2answers
280 views

How can Monolithic kernel based OS are faster the Microkernels?

I have been studying about OS and currently, I am on "types of the kernel". Now in the book and some websites are saying Monolithic kernel-based OS is faster, but how are they faster than ...
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2answers
234 views

How does a process get notifications from the operating system?

In UIKit framework, there are methods associated with app’s life cycle events like applicationWillEnterForeground(_:) which are called at appropriate times. How can I make a process receive such ...
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5answers
450 views

Is an OS compiled every time it boots?

Is an OS compiled every time it boots, or is it compiled once and the result used every time the OS is (re)booted? When users change settings, is the compiled kernel modified at all? If I am the one ...
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504 views

How does an OS limit a program capabilities, if it's working directly with the cpu?

When a program loads into memory and starts running, the cpu loads each instruction from the code and executes the instruction based on the opcode and the arguments, so, the program interracts so to ...
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2answers
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What does the inode point to in case of a device file other than the disk?

I know that the inode points to the actual disk blocks in the case of the normal file system. But what does it point to in the case of .... say .... the terminal device file. Does it point to the ...
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1answer
91 views

Trick or technique to allocating variables given only one "memory store"?

I have a problem where I am using a Uint32Array in JavaScript as a store: const store = new Uint32Array(1 << 16) I am going to use this store like a runtime environment. Basically, everything ...
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1answer
33 views

How to check whether module or class is network interface, socket?

Background Simplifying, assume I want to write some tool for code-analysis, which tell me which files - class/module - are/have some kind of network interface(s). No matter if it's REST Controller, ...
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2answers
139 views

Comparing microservice to MINIX microkernel

I'm trying to understand what microservices are and MINIX's microkernel architecture seems to be a good analog. (I'm a systems engineer.) In my understanding: Microservices are like user space ...
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1answer
67 views

How do I find out all modifications made by installing software? [closed]

So I want to find out how to get a list of all modifications made by installing a piece of software. For example. If I install Word, I want to see all directories created, classes registered, dlls, ...
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1answer
168 views

What does it mean for an OS to compile down to a function?

I was reading the Urbit docs and stopped at this paragraph (emphasis mine): The main thing to understand about our ‘overlay OS’, as we call it, is that the foundation is a single, simple function. ...
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0answers
67 views

FreeRTOS based application architecture

I am going to use the FreeRTOS on my hardware platform. My plan is to model individual tasks as C structs containing task execution period, task priority, task stack size, task name and maybe another ...
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1answer
320 views

How do ISRs and user threads synchronize and share data?

My question is more of educational than an actual coding problem. I tried searching the web, but got little help. I am trying to learn how to write ISR and understand how they interact with user ...
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1answer
70 views

How are symbols resolved in dynamic linking and loading?

I'm a CS student, and I'm doing a project on shared libraries and dynamic linking/loading. One of the questions I have to answer is how symbols are resolved with dynamic linking/loading. I've scoured ...
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1answer
217 views

How is a software able to read a network file faster than it appears to be possible?

Note this is a general, conceptual question about performance optimization. motivated by the following real-world case. I have a file on a Windows network drive that has a 100Mbps limt; it is a ...
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4answers
174 views

Would it be possible to abstract multi-threading ability for programs not originaly designed for such?

Would it be feasible to provide (or further) multi-core threading ability for programs that weren't originally designed for such? And doing so by creating a "virtual" CPU core (or for i7's with ...
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0answers
114 views

Is it possible to implement insert file operation in modern extent-based filesystems?

The problem was already discussed here. But there was not consensus on this topic. I have some thoughts on how insert operation can be implemented for some popular file systems. If FS has extent-...
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1answer
127 views

Are all sockets implemented as per the Berkeley sockets specification?

Are all sockets implemented as per the Berkeley sockets specification in all platforms or languages? What I am trying to understand is; is this the only standard for sockets implementation or there ...
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3answers
200 views

How do you optimally and securely isolate processes when building an operating system from scratch?

I am trying to build software in JavaScript that emulates an operating system. For all intents and purposes, it is an operating system, even though it is JavaScript and we are running in the Node.js ...
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3answers
722 views

Multiprocessing vs multithreading

During my last job interview which was about half year ago, the technical guy asked me, whether the better option is to use e.g. 100 processes to do some work, or only one process but with 100 threads....
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561 views

Where is the difference with client-socket port and server-socket port?

If we decided to create a (TCP) socket-server (for example) on port 12336 imagine it like a: socket.bind(12336) and then to create a (TCP) client-socket for it, like a: socket.connect("12.34.56.78"...
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1answer
271 views

How exactly are drivers developed, distributed, & utilized?

If operating systems use 'drivers' to communicate with external devices, does that then mean that OS's (like windows, linux, & osx) have to come prepackaged with drivers for every single external ...
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1answer
147 views

How swap space works in this example?

Say I have total RAM memory of 1GB , HD of 10 GB with 250 MB swap space Say I have two files(f1 and f2) each of 500 MB opened on my my laptop. Now both files are in memory and have consumed 1 GB of ...
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1answer
726 views

What is the difference between a Page Table Entry and a Memory Descriptor List?

The definition of a MDL from Microsoft is: The operating system uses a memory descriptor list (MDL) to describe the physical page layout for a virtual memory buffer. The definition of a Page ...
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Relationship between the C standard libraries and Java standard libraries

Which is the relationship between the standard libraries of C language and the standard libraries of other software platforms, e.g. Java, .NET, Python? Do the Java (.NET and Python) standard libraries ...
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1answer
3k views

System Call Interface and operating system API

What is the difference between operating system API and system-call interface ? I have read at many places that both act as interface between program and the kernel. Then what is the actual ...
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1answer
52 views

Interested in contributing to ChromiumOS: What steps should I take to prepare? [closed]

I'm a hobbyist developer of 16 years and would like to start contributing to the ChromiumOS project. I have extensive experience in developing for mobile and embedded devices, so my skill set is ...
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1answer
202 views

Making execution of Python script fool-proof beyond adding shebang

Assume that a Python package (available via PyPI) is too difficult for novice users to utilize. Specifically, typing python2 path_to_package/start_GUI.py in the command line, which opens a TKinter GUI,...
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1answer
449 views

Is memory allocation hardware handled or OS?

I am currently working on a bare metal project with an arm processor using GCC arm compiler. If I call malloc, is the allocated memory tracked in the MMU? For some reason I had assumed an OS typically ...
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1answer
294 views

Why non-mainstream OSes don't adopt Linux hardware drivers?

Non-mainstream OSes (Genode, BSD, Haiku, etc.) tend to have problems with drivers availability/support. Why don't they reuse Linux drivers? I would imagine they could provide some ABI compatibility ...
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2answers
155 views

How did old OSs create or expand a segment in memory without issues?

On an 8086 CPU before the flat memory model had been adopted, when the OS wanted to create a new segment for a process, how did it know what virtual memory ranges were already covered by existing ...
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2answers
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Do operating systems implement techniques to ask programs to give up non-vital memory in times of shortages?

When a system is running low on available memory can it ask programs in general to give up any non-vital memory without shutting down. Like a process signal which causes the processes to yield any ...
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How does an Operating System gets allocated its first memory space [duplicate]

Going through osDev.org, I managed to write a small kernel that outputs a memory address, similar to this: #include <stdio.h> int main() { size_t a = 2; size_t *p = &a; printf("...
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357 views

Daemon vs worker and when to use what?

(Note that, below, I am frequently using term "daemon or worker" just to indicate that I dont know which word to use as I dont know the exact difference between them in the context explained below.) ...
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1answer
251 views

What is the difference between writing in assembly vs converting high level language into assembly using compiler?

So i heard that in modern operating systems and device drivers, some parts of them are still written in assembly for better memory optimisation and speed but do developers actually write it in ...
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2answers
366 views

producer-Consumer with Signaling Architecture in a Real-Time Operating System (RTOS)

I'm developing a real-time system by making use of an mbed-OS (RTOS for ARM architecture). I'm not a software engineer and I want to know whether the following solution is practical or not, and how to ...
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1answer
125 views

Regarding system interrupts and timers. Why programs sometimes still run when OS asks you to terminate or keep it going?

I'm reading (just started) "Operating systems concepts" by Silberschatz, Galvin and Gagner and something called my attention when reading a basic primer on "timer" (1.5.2 on the book). It says: As ...

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