General questions about (UNIX) OS architecture

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2
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1answer
21 views

Minimizing hardware interrupts

I am using a modified Linux kernel as a soft real-time OS, on a system that has an architecture like this: CPU1 and CPU2 have 8 cores each. I have 4 processes that need to be run with minimum ...
2
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2answers
103 views

Are system calls the only way to interact with the Linux kernel from user land?

Are there any other interfaces, e.g. the /proc filesystem?
2
votes
1answer
18 views

Structure of graphical modules in Linux Lubuntu

I am trying to understand the layers of the Linux GUI system. I am running a netbook with Lubuntu, and I was told it's running LXDE as desktop environment. However, there are processes with 'gnome'. ...
3
votes
2answers
49 views

Process in user mode switch to kernel mode. Then the process will have root privileges?

According to http://www.linfo.org/kernel_mode.html in paragraph 7: When a user process runs a portion of the kernel code via a system call, the process temporarily becomes a kernel process and is ...
1
vote
1answer
42 views

Daemons fall into what category?

Above system call, there are library routines, utilities and applications. Do daemons fall into any of these categories or they have their own category?
1
vote
1answer
31 views

Are application layer protocols part of library routines?

Where do application layer protocols reside? Are they part of library routines of language e.g. C, C++, Java? As goldilocks says in his answer, this is about the implementation of application layer ...
13
votes
2answers
1k views

How are system commands like ls created?

I'm a *nux newbie and I have some doubts regarding *nix. I don't know which type of executable file is ls, whether it is .sh or .ksh or any other kind of system executable if it is, what is that? ...
2
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6answers
121 views

When does a shell get executed during the linux startup process

I do not understand when does a shell, lets say bash, get executed, which program runs bash initially first.
3
votes
3answers
62 views

Why are file handles a scarce resource?

I feel like every tutorial I read on resource management in server settings starts by asserting that file handles are a scarce resource, and we should therefore aim to keep the list of open files to a ...
4
votes
1answer
82 views

What is the default or most commonly used multiprocessing model in Linux? Symmetric or Asymmetric?

What the multiprocessing model for Linux? Is there a default or most commonly used model? Is it similar or very different from say BSD or even the MS Windows kernel? If SMP is used normally, can ...
15
votes
1answer
173 views

How do keyboard input and text output work?

Suppose I press the A key in a text editor and this inserts the character a in the document and displays it on the screen. I know the editor application isn't directly communicating with the hardware ...
5
votes
1answer
46 views

What are the equivalent architecture of alphanumeric numbers in Debian?

On the Debian website, I found a list of the releases of Debian associate with alphanumerical architectures. Do you know to what those architectures numbers and letters stand for?   
3
votes
2answers
159 views

How to check Linux kernel?

I want to install a package and it has different versions for different OS. The description in the package site is like this X86-64 Linux 3.0 Kernel I looked it up and found people saying to use ...
2
votes
1answer
72 views

Interpret the output of lstopo

I have a output from lstopo --output-format txt -v --no-io > lstopo.txt for a 8-core node in a cluster, which is https://dl.dropboxusercontent.com/u/13029929/lstopo.txt The file is a text drawing ...
1
vote
2answers
66 views

What is a windowing system?

Can someone provide me with a very clear and practical example of a "windowing system"? I was reading on Linux, and although I've always known that it's a kernel, I didn't really know what a kernel is ...
1
vote
0answers
52 views

Which Unixes support cross-device filesystem links (in particular for rename)?

Just read the following on the FreeBSD man page for the rename syscall: ... [EXDEV] The link named by to and the file named by from are on different logical devices (file systems). Note that ...
3
votes
3answers
194 views

Rings and run levels

The question stated below might not be technically correct(misconception) so it would be appreciable if misconception is also addressed. Which ring level do the different *nix run levels operate in? ...
1
vote
2answers
173 views

Debian Wheezy problem with packages and architectures

I recently installed Debian wheezy on my desktop PC. Here is the uname -a command: Linux devnet 3.2.0-4-amd64 #1 SMP Debian 3.2.46-1+deb7u1 x86_64 GNU/Linux Once the installation finished, I ...
2
votes
1answer
483 views

child process does not inherit the pending signals from the parent after a fork system call, why?

Could anybody please tell me the reason to why pending signals are not inherited by the child process? On the other hand, the child process inherits the signal handlers and signal mask from the ...
1
vote
1answer
495 views

Cannot install ia32-libs-i386

I'm trying to install ia32-libs-i386, but it's giving me this error: Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be ...
4
votes
1answer
396 views

How can I build a rpm for i386 target on a x86-64 machine?

I am building an rpm using rpmbuild command as: rpmbuild -bb --root <DIRECTORY> --target i386 --define "_topdir <DIRECTORY>" <specfile>.spec When I use my SLED 10 SP3 x86 machine, ...
4
votes
2answers
89 views

When I move a file to a different directory on the same partition, does the file's data actually move on disk?

I could see it going both ways. If the filesystem stores it's directory structure and list of files in each directory, and then points to the disk location of each of the files, it shouldn't require ...
1
vote
1answer
207 views

Can 32-bit and 64-bit CentOS 6.4 servers both be AD domain controllers for the same domain?

If I have two CentOS 6.4 servers, one i386 and the other x86_64, running Samba 4.0.7, will they replicate domain controller data with each other (and from a Windows Server 2003 AD DC) without any ...
7
votes
1answer
196 views

How signals work internally?

In general, to kill processes we generate signals like SIGKILL,SIGTSTP etc. But how is it known who ordered that particular signal, who has sent it to a particular process, and in general how do ...
2
votes
2answers
90 views

Why do we need two file descriptors when creating an unnamed pipe?

I've been reading about unnamed pipes and as I understood them they're implemented as a buffer in memory. When creating the pipe I need to pass an array of size two and it returns two pointers (file ...
2
votes
4answers
328 views

How do file permissions/attributes work? Kernel-level, FS-level or both?

A question that occurred to me earlier: are file permissions/attributes OS- (and therefore kernel-) dependent or are they filesystem-dependent? It seems to me that the second alternative is the more ...
10
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2answers
700 views

How does a Linux terminal work?

If you fire up a terminal and call an executable (assuming one thats line oriented for simplicity) you get a reply to the command from the executable. How does this get printed to you (the user) does ...
2
votes
3answers
388 views

How I can emulate a big endian platform on a x86?

I need to get a big endian platform to develop with gcc and g++, what is a solution for that? I know that the SPARC is one of those big endian architectures, but I have no idea what OSs can run on it ...
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2answers
233 views

Why is the UNIX kernel so crucial? [closed]

More specifically, how is the UNIX kernel treated differently from other parts of the Operating System?
0
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2answers
62 views

How many types of architectures and OSes

I am trying to write a script python script that is supposed to run across all linux based OSes. The python script invokes executables of few existing tools(for example pathload and iperf) that I have ...
3
votes
1answer
241 views

How to know which commands are executed when I do something in GUI

This is for academic purpose. I want to know which commands are executed when we do something in GUI, for example creating a folder. I want to show that both the mkdir shell command and create folder ...
2
votes
3answers
2k views

How does the set-user-ID mechanism work in Unix?

Can someone please explain the set-user-ID mechanism in Unix ? What was the rationale behind this design decision? How is it different from effective user id mechanism ?
2
votes
1answer
229 views

Concept of memory mapping in Unix like systems

Can some one explain in an easy to understand way the concept of memory mappings (achieved by mmap() system call) in Unix like systems ? When do we require this functionality ?
0
votes
1answer
278 views

File permission mechanism in Unix like systems

Can some one please explain with a an example the file permission mechanism in Linux and other Unix like systems ? What are the nine bits for ? Why do we have a group id for a user as well as for a ...
4
votes
2answers
2k views

Difference between system calls and library functions

I have been through the answer of this question but do not quite understand the difference between system calls and library functions. Conceptually, what is the difference between the two?
1
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0answers
446 views

Install CentOS in a VirtualBox to a Compact Flash and use it on a mini PC

I got into a very specific situation and want to get to know your opinions. I have got a mini PC with Intel Atom processor which should run CentOS with an upgraded kernel to 3.x and some ...
-1
votes
1answer
626 views

Hurd vs Plan9 vs Linux vs eCos vs FreeRTOS what are the main differences specially with Hurd?

Hurd is actually not Unix nor Linux. But more superior says. Where Plan9 and Linux are in the range of Unix/Linux. eCos and FreeRTOS is also completely not unix/linux. What is the main differences ...
3
votes
3answers
1k views

Which arch linux should I download?

I'm going to install Arch linux yet I have to choose between several architectures my computer has. I have an aluminium macbook pro, with a 2.3 GHz Intel Core i5 processor. . The intel webpage tells ...
4
votes
9answers
570 views

Metaphor for the concept of shell?

I'm finding myself helping out some classmates in my computer science class, because I have prior development experience, and I'm having a hard time explaining certain things like the shell. What's a ...
5
votes
2answers
476 views

What's the difference between /etc/rc.d/rc*.d and /etc/rc*.d

I know that rc*.d directories are used at startup, or reboot, or so on time, for starting or stopping programs. Can anybody explain me what's the difference between the rc*.d folders placed under the ...
3
votes
4answers
538 views

What are the books about creating own *nix OS? [closed]

I want to create my own Unix OS. Is there any book that I can learn from, from start?
2
votes
2answers
731 views

How to determine bitness of hardware and OS?

Output of uname -a on my RHEL 5.4 machine is: Linux <machine name> 2.6.18-164.el5 #1 SMP Tue Aug 18 15:51:48 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux Does it mean that hardware is 64 bit ...
7
votes
3answers
2k views

Which Scheduling algorithm is used in Linux?

Recently in an interview I was asked about the Scheduling algorithm used by Linux Operating system. What is the algorithm used any why? Also, what algorithm is used in in real-time operating systems ...
8
votes
4answers
2k views

How are directories implemented in Unix filesystems?

My question is how directories are implemented? I can believe a data structure like a variable e.g. table, array or similar. Since UNIX is Open Source I can look in the source what the program does ...
15
votes
4answers
2k views

How to understand pipes

When I just used pipe in bash, I didn't think more about this. But when I read some C code example using system call pipe() together with fork(), I wonder how to understand pipes, including both ...
7
votes
1answer
5k views

What are software and hardware interrupts, and how are they processed?

I am not sure if I understand the concept of hardware and software interrupts. If I understand correctly, the purpose of a hardware interrupt is to get some attention of the CPU, part of implementing ...
8
votes
3answers
2k views

What is the relationship between system calls, message passing, and interrupts?

I am reading the Wikipedia article for process management. My focus is on Linux. I cannot figure out the relation and differences between system call, message passing and interrupt, in their concepts ...
9
votes
2answers
1k views

Interruption of system calls when a signal is caught

From reading the man pages on the read() and write() calls it appears that these calls get interrupted by signals regardless of whether they have to block or not. In particular, assume a process ...
2
votes
2answers
647 views

Removing zombie process from the process table

Can somebody please explain when parent process receives the exit status of a dead child process via wait, who actually reallocates the memory of the child process and removes it from the process ...
0
votes
1answer
266 views

Which FreeBSD version or ISO for Dell R310?

When I try to install FreeBSD I always get confused as to which iso is the correct one for Rack mounted servers. In their download choices, there are too many versions of FreeBSD Which one is the ...