Everything about UNIX kernels: development, configuration, compilation, design, etc.

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1answer
585 views

What are the main differences between Unix and Linux kernels today?

I know that many of the same programs run flawlessly on top of both kernels. I know that historically, the two kernels came from different origins. I know philosophically too that they stood for ...
5
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2answers
3k views

Can I detect if my custom made kernel was built with module support?

I have been provided with a vendor supplied minimal linux installation. From an answer to a previous question I discovered that it is possible to build a kernel with or without module support. I have ...
4
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3answers
438 views

Why do people call Linux a kernel rather than an OS?

Why do people refer to Linux as a kernel rather than an operating system? To the best of my knowledge, the kernel is one part of the operating system.
4
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3answers
945 views

Debugging ethernet before NFS boot

I'm trying to boot Linux from U-boot on an embedded ARM board using a filesystem on a remote machine served via NFS. It appears that the ethernet connection is not coming up correctly, which results ...
-1
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2answers
707 views

Generate major page faults

Is it possible to generate major page faults in the linux kernel at will? Can a program be written such that it is guaranteed to cause a major page fault on it's execution.
7
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1answer
626 views

Linux kernel 3.3 power regression

I am using Fedora 16 in my DELL n4110. I recently upgraded the kernel from 3.2 to 3.3. In contradiction to the official claim, my system still drains battery as hell. It only provides 1:30 to 2 hrs of ...
5
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1answer
155 views

How does the kernel prevent a malicious program from reading all of physical RAM?

If I write a program that tries to read memory at every possible address, and I run it on a "full" Unix, it will not be able to access all of the physical RAM. But how does the operating system ...
4
votes
1answer
185 views

/proc/config.gz is of 0 bytes

I have an Android TV stck I compiled Linux for IT from https://github.com/Galland/rk3x_kernel_3.0.36 But when I booted that Image I found /proc/config.gz is of 0 bytes can some please explain how ...
4
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2answers
2k views

Restricting memory area for linux kernel

I am running ltib Linux on P1022RDK (P1022 Core) platform. I have 512 MB = 0x20000000 memory. I want my Linux kernel to use the second half of the board memory (i.e from 256 MB to 512 MB) and want the ...
3
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1answer
132 views

How security programs like firewall, IPS and IDS have access to network data?

It is said that kernel responsible for the transport, internet and network access layers for a network data. Then, the network data is passed on the appropriate process based on port number. How ...
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2answers
106 views

why do some network cards need to load external firmware?

I have read this question/answer, but I still do not understand why some network cards work perfectly well without any additional firmware, whereas others need to load firmware to work. As a specific ...
2
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3answers
452 views

Why is kernel boot starting too late

Log message from ARM Cortex A9 based board. Running linux. [Sat Apr 12 19:33:50.207 2014] [Sat Apr 12 19:33:50.207 2014] [Sat Apr 12 19:33:50.207 2014] U-Boot 2013.07 (Apr 09 2014 - 12:31:52) ...
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1answer
282 views

How to compile a third party driver into the kernel?

I am using Linux Mint 17.2 on Toshiba c640. As my LAN driver is no more functional, I am using a USB to LAN converter which was provided with some driver installation files. Every time i want to use ...
1
vote
1answer
171 views

extract Embedded initramfs

I have a kernel in which one initramfs is embedded. I want to extract it. I got the output x86 boot sector when I do file bzImage I have System.map file for this kernel image. Is there any way to ...
1
vote
1answer
71 views

How to modify huge patch file properly?

I have this patch. I want to disable patching of Makefile and drivers/video/logo/logo_linux. What is best way of doing this? Do I edit it, and delete that specific entries? If so, is there a tool ...
1
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2answers
569 views

TLB cache flusing when a page is swapped out

I recently heard that Linux simply flushes the TLB cache when the corresponding data in that physical address is swapped out, resulting in underutilization of the TLB. I don't know whether all OSes do ...
1
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0answers
507 views

Make and apt-get Have Stopped Working

So I downloaded the non-free broadcom driver(b44) for my debian install, however when I try to make it I get the following error: make make -C /lib/modules/2.6.32-5-amd64/build ...
25
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4answers
38k views

How is an Interrupt handled in Linux?

I just know that Interrupt is a hardware signal assertion caused in a processor pin. But I would like to know how Linux OS handles it. What all are the things that happen when an interrupt occurs?
54
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4answers
3k views

How to compile the C compiler from scratch, then compile Unix/Linux from scratch

Let's say I work for a large services organisation outside the US/UK. We use UNIX and Linux servers extensively. Reading through this article it mentions that it would be easy to insert a backdoor ...
38
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5answers
21k views

What is the difference between kernel drivers and kernel modules?

When I do a lspci -k on my Kubuntu with a 3.2.0-29-generic kernel I can see something like this: 01:00.0 VGA compatible controller: NVIDIA Corporation G86 [Quadro NVS 290] (rev a1) Subsystem: ...
36
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5answers
13k views

Who's consuming my inotify resources?

After a recent upgrade to Fedora 15, I'm finding that a number of tools are failing with errors along the lines of: tail: inotify resources exhausted tail: inotify cannot be used, reverting to ...
22
votes
4answers
1k views

What exactly happens when I execute a file in my shell?

So, I thought I had a good understanding of this, but just ran a test (in response to a conversation where I disagreed with someone) and found that my understanding is flawed... In as much detail as ...
27
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4answers
35k views

How to cause kernel panic with a single command?

Is it possible to cause a kernel panic with a single command line? What would be the most straightforward such command for a sudoing user and what would it be for a regular user, if any? Scenarios ...
19
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1answer
21k views

How to use Linux kernel driver bind/unbind interface for USB-HID devices?

First background. I am developing a driver for Logitech game-panel devices. It's a keyboard with a screen on it. The driver is working nicely but by default the device is handled by HID. In order to ...
26
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1answer
29k views

What is kernel ip forwarding?

I have seen on many blogs, using this command to enable IP forwarding while using many network security/sniffing tools on linux echo 1 > /proc/sys/net/ipv4/ip_forward Can anyone explain me in ...
15
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4answers
559 views

How do I learn what I can do with /proc and /sys

I'd like to know more about the advanced uses of the /proc and /sys virtual filesystems, but I don't know where to begin. Can anyone suggest any good sources to learn from? Also, since I think sys has ...
15
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5answers
13k views

Use of O_DIRECT on Linux

If this question is too programmer oriented, let me know. I wonder if there are people familiar with the O_DIRECT flag for the open() system call on Linux 2.6? Linus disparages its use, however high ...
11
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1answer
5k views

Blocking kernel updates with dpkg

I'd like to block all distribution-shipped kernel updates due to a nasty thing that recently happened to me. (I'm on a Ubuntu 12.04 amd64 derivative.) I'd like to block all updates to installed ...
10
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3answers
12k views

How does the Linux kernel handle shared IRQs?

According to what I've read so far, "when the kernel receives an interrupt, all the registered handlers are invoked." I understand that the registered handlers for each IRQ can be viewed via ...
25
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4answers
61k views

What's the difference of dmesg output and /var/log/messages?

AFAIK dmesg shows information about kernel and kernel modules, and /var/log/messages also shows information produced by kernel and modules. So what's the difference? Does /var/log/messages ⊂ output ...
15
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3answers
4k views

Is USB-to-USB data transfer between two Linux OSes possible?

I want to create a USB-to-USB data transfer system in Linux (preferably Ubuntu). For this I want to use no external hardware or switch (except this cable). It's going to be like mounting a USB drive ...
24
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3answers
819 views

How did the Linux Kernel project track bugs in the Early Days?

We all know that Linus Torvalds created Git because of issues with Bitkeeper. What is not known (at least to me) is, how were issues/tickets/bugs tracked up until then? I tried but didn't get anything ...
24
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1answer
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High CPU usage with CFS?

I asked a previous question to try and isolate the source of an increase in CPU usage when moving an application from RHEL 5 to RHEL 6. The analysis that I did for that seems to indicate that it is ...
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2answers
2k views

Heavy write activity on SSD nukes system performance

I've noticed that when I do heavy write applications, the whole system slows down. To test this further I ran this to do a (relatively) low-CPU, high disk activity: john -incremental > file_on_SSD ...
10
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3answers
7k views

How to read the in-memory (kernel) partition table of /dev/sda?

I accidentally overwrote my /dev/sda partition table with GParted (full story on AskUbuntu). Since I haven't rebooted yet and my filesystem is still perfectly usable, I was told I might be able to ...
14
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1answer
15k views

using devtmpfs for /dev

I have noticed the following option in the kernel: CONFIG_DEVTMPFS Device Drivers -> Generic Driver Options -> Maintain devtmpfs to mount at /dev And I see that it is enabled by default in ...
10
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1answer
7k views

Real time processes scheduling in Linux

I have been learning some scheduling concepts. Currently my understanding so far is as below. There are real time processes and non real time processes. Non real time processes can have nice values ...
10
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3answers
16k views

How can I know which IRQ is responsible of high CPU usage

I've moved a server from one mainboard to another due a disk controller failure. Since then I've noticed that constantly a 25% of one of the cores goes always to IRQ however I haven't managed myself ...
9
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2answers
4k views

Adding a new System call to Linux 3.2.x with a loadable kernel module [closed]

I want to add a particular new system call in the linux kernel 3.2.x but as a loadable kernel module (as I don't want to recompile the kernel again and again) I read through many posts on internet ...
14
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1answer
3k views

Why does Red Hat Linux use such an old kernel?

Why does RHEL (and its derivatives) use such an old kernel? It uses 2.6.32-xxx, which seems old to me. How do they support newer hardware with that kernel? As far as I know these kind of distributions ...
14
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2answers
17k views

How to include local header files in linux kernel module

Say I have a module mymod with source files as follows: src/mod/mymod.c src/inc/mymod.h I try to include mymod.h as follows #include <mymod.h> My makefile contains EXTRA_CFLAGS= ...
8
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3answers
25k views

what is pts/0 and (:0.0) in linux by type who am i

When I type the command: [root@degeneration Desktop]# who am i root pts/0 2013-04-12 15:08 (:0.0) What is pts/0 and what is meant by (:0.0)?
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2answers
5k views

How can you determine which process scheduler is being used? [duplicate]

I.e. is it the O(1) scheduler, the CFS scheduler, or an older one?
5
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1answer
2k views

Silent booting Linux from u-boot

For security reasons I have to boot Linux from u-boot with all output hidden (silently) until a password is entered. I've configured uBoot to do this correctly using the CONFIG_AUTOBOOT_KEYED macro ...
23
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3answers
25k views

Why would the kernel drop packets?

I interrupted tcpdump with Ctrl+C and got this total summary: 579204 packets captured 579346 packets received by filter 142 packets dropped by kernel What are the "packets dropped by kernel"? Why ...
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2answers
3k views

/proc/sys vs /sys/modules/mod/parameter

I've been wondering for last few days how exactly does it work. We can set kernel runtimes parameters using sysctl or echo boolen 1> /proc/sys/module/exactParameter but in ...
8
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1answer
6k views

What is the loopback interface

What is the loopback interface and how does it differ from the eth0 interface? And why do I need to use it when mounting an ISO or running a service on localhost?
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4answers
6k views

How many cores can Linux kernel handle?

I'm interested in theoretical limits, perhaps with examples of systems having huge numbers of CPU's.
6
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2answers
897 views

what's the format spec for `ss -D `?

Background of the question: I am trying to sum up the total bandwidth, but ss -i cleverly converted numbers to more readable format like Kbps/s or Mbps/s, which is not accurate. So does ss -o with ...
6
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4answers
6k views

Prevent claiming of novelty usb device by usbhid so I can control it with libusb?

I have a USB rocket launcher that I wish to experiment with through libusb. However, libusb cannot claim the interface; presumably because the output of usb-devices lists 'usbhid' as the driver for ...