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

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19
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3answers
291 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 ...
11
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2answers
1k 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 ...
4
votes
2answers
3k views

How to know if a network interface is tap, tun, bridge or physical?

As far as i know, there are 4 main types of network interfaces in linux: tun, tap, bridge and physical. When i'm doing sys admin on machines running KVM, i usually come accross tap, bridge and ...
12
votes
1answer
2k 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 ...
12
votes
1answer
7k views

Buffer size for capturing packets in kernel space?

Going through the man page of tcpdump, it seems kernel can drop the packets if the buffer is full. I was wondering if: that size is configurable and/or where can I see the size for my distro? From ...
9
votes
1answer
2k 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 ...
9
votes
3answers
9k 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 ...
7
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2answers
3k 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 ...
3
votes
3answers
13k 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)?
19
votes
5answers
3k views

Where does uname get its information from?

Where does uname really get its information from? I figure this is something that should be straightforward. Unfortunately, I can't find any header containing just that information. Say someone ...
10
votes
1answer
14k 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 ...
9
votes
2answers
10k 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= ...
7
votes
2answers
14k views

yum installs kernel-devel different from my kernel version

I am attempting to install the VMWare player in Fedora 19. I am running into the problem that multiple users have had where VMware player cannot find the kernel headers. I have installed the ...
7
votes
3answers
4k 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 ...
7
votes
1answer
5k 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?
6
votes
2answers
471 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
votes
4answers
3k 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.
5
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3answers
4k 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 ...
4
votes
1answer
2k views

Debian 6.0 system with 2.6.39 kernel dropping packets, sandy bridge hardware

I recently migrated an existing Debian system to new hardware, a core i3 chip running on an intel sandy bridge motherboard. I’m experiencing a very strange problem; when I ping my router, about 50% of ...
9
votes
1answer
4k views

Isolating cause of higher CPU usage on RHEL 6 vs RHEL 5

I'm currently looking to move our system from RHEL 5 to RHEL 6, but I've run into a snag with unexpectedly high CPU usage on the RHEL 6 machines. It appears that this may be due at least in some part ...
8
votes
3answers
5k views

Can vmlinux be used instead of uImage?

I want to use an uncompressed kernel image and boot the BeagleBoard. Generally I use uImage to boot the kernel which is in compressed format. How do I use an uncompressed kernel image?
6
votes
2answers
673 views

My process was killed but I cannot understand the kernel notice

I have a custom application running on an embedded x86 setup (built using buildroot and uClibc). The application has been running fine but this morning when I returned to work I discovered my process ...
5
votes
3answers
1k views

How can I tweak the kernel for total swap out?

I would like to deploy the following swapping policy: By default all pages in memory should also be in swap space. When a page in memory is changed (i.e. dirty), the page should be written out as ...
4
votes
1answer
985 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 ...
4
votes
1answer
2k views

usb kernel module does not load on demand but works fine with insmod and modprobe from the shell

I have a USB Linux Kernel module that compiles and builds. Running insmod loads my module and dmseg and tail -f /var/log/debug shows me it works as expected. Running depmod -a then modprobe from the ...
4
votes
3answers
1k 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? ...
4
votes
2answers
2k 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
votes
2answers
531 views

Is it normal that a restart is required to mount USB after a kernel upgrade?

Sometimes I see the Linux kernel being mentioned in the list of upgrades, when running pacman -Syu (updating my packages in Arch Linux). Whenever this happens, after installation of the packages, I ...
4
votes
2answers
14k views

Command to install linux headers fails

I need to install my linux headers for an Nvidia driver install. But I get an error when doing so: peter@peter-deb:~$ sudo apt-get install linux-headers-$(uname -r) Reading package lists... Done ...
3
votes
3answers
170 views

API with no system calls

The book 'Understanding Linux Kernel' says that 'for something abstract such as math functions, there may be no reason to make system calls'. Can any one please explain how is a system call not ...
3
votes
1answer
9k views

/proc/sys/kernel/hung_task_timeout_secs error

I am building a CentOS 6.2 webserver on a Hyper-V Cluster and have hit a major issue. The current setup is this: Operating System: CentOS 6.2. Minimal Server Install Installed software includes: ...
2
votes
2answers
3k views

How do I cause a watchdog reset of my embedded Linux device

Is there a command like vi > out vi | out That I could use to cause a watchdog reset of my embedded linux device?
2
votes
1answer
113 views

Is there any method to mount a block of memory as a filesystem in linux?

I have a question,in linux, is there any method to mount a block of memory as a filesystem? For example, in X86 architecture, when power on, I reserve a block of memory about 8 Mbytes, and then when ...
1
vote
1answer
201 views

what is a Kernel? [closed]

I'm learning Unix from the Unix Architecture book by Maurice J Bach. So if my question seems too stupid, please do bear with it. I read a few related questions but I would like a more simple ...
1
vote
1answer
4k views

Problem compiling a driver : “No rule to make target”

First of all I am running a CentOS 6.4 installation. My computer is a laptop and I am trying to install the drivers for my ethernet card, because this week end I lost my ability to connect to the ...
1
vote
0answers
75 views

Decreasing mouse sensitivity at kernel level

I have developed a custom-GUI Server, which runs on virtual console of Linux.For mouse-handling purpose, it reads the mouse device file /dev/input/mice and retrieves the event data and updates ...
1
vote
1answer
2k views

__modver_version_show undefined error during make

Platform: Ubuntu 11.10 64bit Kernel to be compiled: 3.2.1 Error after make: ERROR: "__modver_version_show" [drivers/staging/rts5139/rts5139.ko] undefined! To solve this I copied the .config file of ...
0
votes
2answers
492 views

Error Installinig Kernel on Centos (from Source)

I am running GNU/Linux (Centos 6) on kernel 2.6.32-431.17.1.el6.x86_64. I am trying to update the kernel to 3.2.61. I performed the following steps inside the 3.2.61 folder structure: make ...
15
votes
3answers
3k views

Why don't you need to update drivers? (Or do you?)

In my life I've not once updated drivers on any of my Linux systems, though they have all been desktops. A friend was asking me why one does not need to update Linux drivers and I found myself unable ...
8
votes
6answers
2k views

How to find information about the system/machine in Unix?

I have always found it difficult to find information about the system itself in Unix, whether it be Which OS I am using (version number and all, to compare it with the latest available builds)? ...
7
votes
2answers
2k views

An oom killer thats baffling me

I am not able to understand why would kernel issue this oom killer when I see enough memory is available: Also why are there so many kernel cache pages allocated? I say enough memory is available ...
7
votes
1answer
1k views

User Kernel split in 64bit Linux

What is the default user/kernel split in the 64bit linux ? I read Documentation/x86_64/mm.txt (which someone pointed out), but I could not make out. Can somebody provide a direct answer (something ...
6
votes
3answers
3k views

how is page size determined in virtual address space?

Linux uses a virtual memory system where all of the addresses are virtual addresses and not physical addresses. These virtual addresses are converted into physical addresses by the processor. To ...
6
votes
2answers
12k views

What is the difference between Non-preemptive, Preemptive and Selective Preemptive Kernel?

What is the difference between a "Non-preemptive", "Preemptive" and "Selective Preemptive" Kernel? Hope someone can shed some light into this.
5
votes
2answers
99 views

Making a process read a different file for the same filename

I have an application that reads a file. Let's call it processname and the file ~/.configuration. When processname runs it always reads ~/.configuration and can't be configured differently. There are ...
5
votes
3answers
3k views

ACPI problem with recent kernels

In recent versions of popular Linux distributions (Ubuntu, Fedora, Mint, Debian) I always have to put acpi=off into the kernel parameter list before I want to boot the computer. This happens to both ...
5
votes
2answers
1k views

ZONE_NORMAL and it's association with Kernel/User-pages?

Above is presented a case where I have only 512 MB of physical memory. What I have read up so far, is that ZONE_NORMAL is mapped to the kernel virtual address space as shown. Essentially I have a ...
4
votes
1answer
41 views

git: show which files have changed between kernel 3.18.6 and 3.18.7

I have checked out linux kernel git repository git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git I know how to use git log, git show and similar commands to see ...
4
votes
1answer
163 views

why would there be a load of 5 if there are zero processes in the runq?

This doesn't make sense to me, why would there be a load of 5 if there are zero processes in the runq? 12:00:01 AM runq-sz plist-sz ldavg-1 ldavg-5 ldavg-15 12:05:01 AM 0 708 ...