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

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6
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2answers
234 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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3answers
2k 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 ...
5
votes
3answers
3k 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
7k 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 ...
8
votes
1answer
3k 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 ...
6
votes
1answer
174 views

Can you explain the entropy estimate used in random.c

/dev/random uses the timings of kernel interupts to add to the entropy pool. The amount of entropy in the pool is tracked in a variable named entropy_count. Here is the relevant snippet of code from ...
6
votes
1answer
842 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 ...
6
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2answers
6k 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 ...
5
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1answer
6k views

disable transparent hugepages

We are installing SAP HANA in a RAID machine. As part of the installation step, it is mentioned that, To disable the usage of transparent hugepages set the kernel settings at runtime with echo ...
5
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2answers
450 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
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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
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2answers
1k 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 ...
3
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3answers
121 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
3answers
366 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? ...
3
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 ...
3
votes
1answer
8k 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 ...
2
votes
1answer
772 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 ...
2
votes
1answer
106 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 ...
13
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3answers
2k 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
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2answers
6k 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
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
3answers
327 views

What defines the maximum size for a command single argument?

I was under the impression that the maximum length of a single argument was not the problem here so much as the total size of the overall argument array plus the size of the environment, which is ...
6
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2answers
1k 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 ...
6
votes
1answer
727 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 ...
5
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2answers
87 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
2k 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
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2answers
9k 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.
4
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1answer
109 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 ...
4
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2answers
1k views

Installing OpenVPN to replace Cisco VPN because Cisco will not work with the kernel I am on or downgrade instead?

I had difficulties installing Cisco5.0 VPN on my Ubuntu 10.04 LTS. I asked for assistance in this question: link to previous question. The answer is that this Cisco program will run on only older ...
4
votes
1answer
299 views

NetBSD 5.1 NDIS Kernel Compile Error

I have an old Toshiba Satellite 4015CDT, with Pentium II MMX, 32MB RAM, 4GB HDD. It also has one USB 1.0 port, parallel and serial ports, a 3.5" floppy drive and a CD-ROM drive (almost dead). I've ...
4
votes
3answers
1k views

Recompile Kernel to Change Stack Size

I need to recompile my kernel on RHEL WS5 with only two changes. Change stack size from 4k to 8k Limit usable memory to 4096. How do I recompile the kernel without changing anything else but ...
3
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3answers
134 views

Is it mandatory to have a file system and MMU in Linux? [closed]

Suppose I do not need a filesystem and I have only applications where data reloading may not be required - so MMU may be redundant. Can I remove these two items from Linux, and boot the OS ...
3
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2answers
209 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.
3
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2answers
6k 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)?
3
votes
4answers
1k views

Stripped down Kernel for a Laptop

I am a Linux noob, but I am willing to learn. My immediate objective is to compile a small kernel for my laptop without sacrificing usability. I am familiar with the kernel compilation steps (don't ...
2
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3answers
90 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 ...
2
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1answer
578 views

LinuxMint15: Suspend to RAM not working

I just installed LinuxMint15 on an Acer Aspire V3-771G-73638G500Maii. Hibernation works. But suspend to RAM does not. When clicking suspend: After a few seconds the screen goes grey and then off. ...
2
votes
1answer
552 views

Build kernel in one machine, install in another

I want to build my Linux kernel on my host and use it in my VWware virtual machine. They both use the same Ubuntu kernel now. On my Host, I do make and make configure. Then, what files should I copy ...
2
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1answer
6k views

/lib/modules/2.6.37.6/build missing in linux puppy? what should I do?

I am new to linux as of yesterday. I'm using linux puppy to try to get the most out of a 10 year old, slow laptop. I installed it fine, no problems there, but as soon as I try to use my usb dongle's ...
2
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2answers
4k views

Kernel Panic - not syncing: VFS: Unable to mount root fs after new kernel compile

So I've been at this for a while and have been poking around for an answer for a few days, and figure it's about time to ask for help. I am running Ubuntu 10.10 in VMWare Fusion, and have downloaded ...
2
votes
1answer
782 views

Where can I find information on Linux device driver parameters?

I want to work on Linux module programming (Device Drivers). And as a my college project I have to do profiling or benchmarking of a kernel modules based on various parameters. Everywhere I looked, I ...
1
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2answers
122 views

FATAL: Module hello.ko not found

I'm using CentOS-6.5 and default kernel is 2.6.32-431.11.2.el6.x86_64. I downloaded 2.6.32 and built that kernel (under /lib/modules/2.6.32). I wrote a module for simple hello world program. This ...
1
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3answers
97 views

Enabling IP forwarding at kernel compile time

I am compiling a kernel for a router. I know a way to enable IP forwarding in an existing Linux system. At compile time, CONFIG_IP_FORWARD is said to do the same task. I am configuring version ...
1
vote
1answer
94 views

Kernel pppd task hung after running over serial port

I am trying to run the ppp daemon on the console port of my board which has p2020 processor with Linux kernel 2.6.32. After running ppp interface ppp0 is not coming up and I get an error pppd blocked ...
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3answers
891 views

Why kernel 3.6.2 is so much less energy efficient than 3.6.1 on Mint 13?

I noticed, that the power consumption in my ASUS P53E notebook is doubled (from 10W to 20W) when I change from kernel 3.6.1 to 3.6.2 (or later). I use Ubuntu Quantal mainline kernel from ...
1
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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 ...
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2answers
2k 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?
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2answers
1k views

Who wrote the “Linux kernel” (Linus Torvalds and his team)?

Who are the authors of the pure Linux kernel from scratch, which was integrated with GNU tools and formed the full GNU/Linux Operating system in the 1990s? I have read some wiki articles but I haven't ...
0
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1answer
237 views

modpost.h:12:23: fatal error: elfconfig.h: No such file or directory

I am running Ubuntu: #lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 12.04.4 LTS Release: 12.04 Codename: precise Kernel info: 3.8.0-38-generic ...
0
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1answer
129 views

Does an in-kernel firewall sit between the network access layer and Internet layer?

This question is a follow-up to my previous question. Logic for me to says that an in-kernel firewall sits between the network access layer and the Internet layer, because it needs to have access to ...