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

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What does this “general protection fault” in my console mean, and how do I interpret it?

I had a couple of consoles open for other work and when I came back to them they both contained the following: Message from syslogd@Stacey-Windows at Jun 19 09:43:28 ... kernel:[ 4375.127165] ...
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7answers
2k views

What's the difference of the Userland vs the Kernel?

I am trying to understand exactly what is userland? everyone that I ask says: "Anything that is not kernel". but it is not tangible for me. When I am reading that kernel can run that driver on the ...
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2answers
110 views

Debian: get package name for installed file

I'm connected via SSH to a PC running Linux kernel 3.11.1: root@alix:~# uname -r 3.11.1 how can I find out which package installed this specific file or kernel version respectively? I tried ...
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2answers
1k views

Linux freezing guess: keyboard & mouse (Archlinux and Ubuntu)

Linux on my PC is freezing a few seconds after startup. I am unable to use the mouse / keyboard. Neither Ubuntu nor Arch do anything after a few seconds. Windows has been running fine for years now. ...
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5answers
2k 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 ...
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0answers
73 views

Do kernel threads seem to interfere with full tickless mode?

I'm trying to disable local timer interrupts for low latency. I have full tickless mode enabled in the kernel config and I have the boot parameter nohz_full set for the cores in question. However ...
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1answer
80 views

Find out if CPU supports dynamic speed setting

I need to find out in my script if a (potentially legacy) CPU supports dynamic speed setting, and eventually get value of maximum and current speed. What makes it more complicated is that I need to ...
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1answer
610 views

Realtek RTS5209 PCI-E Card Reader only work if card is inserted before boot

Hardware Info Laptop Model: Sony Vaio Pro 13 Problematic Hardware: Bulti-in Realtek Semiconductor Co., Ltd. RTS5209 PCI Express Card Reader Problem description Here is the problem, if I boot with ...
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1answer
3k views

After installing a new Kernel in Ubuntu 14.04, rebooting takes me to busybox initramfs. How do I mount a filesystem after that?

I have a virtual machine with Ubuntu 14.04 in it. I recently built and installed linux-3.14.5 kernel on it, and tried to boot into it, but it drops me to BusyBox v1.21.1 built-in shell. Here's what I ...
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204 views

Updating kernel on a Chromebook to prep for Chrubuntu

Pretty simple question: I have read that by setting my Chromebook to the dev channel, it will install a later kernel. Currently it's 3.4.0, and it'd install 3.8.0 (64-bit, no less). However, after ...
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642 views

Kernel 3.14.1 compilation errors

I installed the kernel 3.14.1 and there seem to be no issues. uname -r 3.14.1-031401-generic However, when I try to go to the folder and try to do a make it fails. I see that multiple files are ...
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1answer
152 views

When is swap triggered or how to calculate swap_tendency?

I'm trying to use Redis for production services and trying to avoiding swapping, which is bad for performance. I had learn that swap is triggered by swap_tendency which is depending on ...
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1answer
82 views

kernel event listener

I wonder if there is something similar to an event listener in UNIX that a program can subscribe to? Specifically I want to know: Start and end times of a user session Start and end of the ...
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1answer
83 views

What causes /proc/<pid>/* resources to become owned by root, despite the procs being launched as a normal user?

I've noticed that some procs, such as bash, have their entire /proc/<pid>/ resources readable by the user who created that proc. However other procs, such as chrome or gnome-keyring-daemon, have ...
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0answers
91 views

Adding IPVS to the kernel

I am trying to setup keepalived on a pair of VPS load balancer servers. I have hit the road block of IPVS not being included with the kernal. IPVS: Can't initialize ipvs: Protocol not available I ...
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0answers
21 views

Intel Xeon stuck at 800mhz CPU Freq on RHEL 6.5 [duplicate]

Currently running into a headache trying to figure out why my CPU speed is stuck as such a low frequency. After doing some research, I found that cpuspeedutil does actually control the state of the ...
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2answers
102 views

How to find out the bad block table offset and how to change it in u-Boot

I am facing a similar problem as this: Kernel does not recognize nand bad blocks marked by u-boot I'm using a friendlyARM micro2440 board that contains the s3c2440 ARM processor. u-Boot has found ...
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2answers
253 views

Porting jvm into the kernel space?

Currently I am playing with the idea of a jvm running in the kernel space, as a (maybe linux) kernel module. I see a lot of advantage of the idea. Of course the biggest advantage of a such system ...
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0answers
42 views

Get log from kernel while loading

There is a arm/omap2-based device without ethernet, UART ports. It has usb connection with host, numeric keyaboard, LCD display. There is working U-Boot and kernel images for this. I'm trying to ...
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1answer
214 views

Library routines in linux kernel

In the linux kernel, there is a section "Library routines" with a snippet shown below: Library routines ---> <M> CRC-CCITT functions <M> CRC ITU-T V.41 functions <M> CRC7 ...
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1answer
137 views

How to check and set “rhash_entries” parameter?

I'm reading this article, and it says: rhash_entries is the size of the hash table. If you don't specify it on the kernel command line, it is computed dynamically based on the memory available on ...
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0answers
141 views

ftdi_sio not pre-installed

I have recently recompiled my Ubuntu's kernel to Linus' most recent one. After rebooting, I tried to connect my computer to a development board via an FTDI FT232 USB-to-Serial converter. It used to ...
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0answers
96 views

How to set sctp_nodelay to enable piggybacking while replying back

Problem: We are hosting a telecom application that receives traffic from the network at > 500 TPS. The packets are piggybacked so each sctp packet contains multiple application layer packets lets say ...
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1answer
301 views

custom kernel and firmware loading

After I have compiled my kernel, and when I type make modules_install, not only are the modules copied into /lib/modules/ but also firmware is copied into /lib/firmware/. The following is the end of ...
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2answers
2k views

Where does make defconfig get its configuration in OpenWrt?

I am compiling an image for wifi devices using OpenWrt. Following the instruction I copy a simple .config file to TOP-DIR. CONFIG_TARGET_ar71xx=y CONFIG_TARGET_ar71xx_generic=y ...
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0answers
53 views

Black screen when kernel boots with vga= parameter

Recently recompiled kernel refuses to do output on the screen if vga parameter was in the list. Without it kernel boots properly as usual, however, before that it changed resolution and RC log ...
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3answers
446 views

Compare two kernel config files from the menuconfig perspective?

I have a situation in which i have two kernel config files (for the same kernel source ). Both of them have a part of the functionality that i need (on one, USB works correctly, on other, the second ...
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1answer
163 views

What is the difference between all and default in kernel setting? [duplicate]

I want to enable reversed path filtering to prevent source ip spoofing on my server. I noticed that I have the following settings at current: net.ipv4.conf.all.rp_filter = 0 ...
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1answer
151 views

MIC not working due to USB bandwidth

Using debian and centos, i get the same error when plugging my USB mic in. In Windows (xp thru 8.1) it works fine. [ 304.237543] usb 2-1.6.2: USB disconnect, device number 6 [ 305.220785] usb ...
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1answer
72 views

How to undo kernel settings?

While trying to read some kernel parameters, I think I have mistakenly set some instead: # sysctl --system -r ^net.*tcp * Applying /usr/lib/sysctl.d/00-system.conf ... * Applying ...
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0answers
106 views

How does one clean up a stale CIFS mount

I have a recurring problem where I need to mount a drive of a Win32 machine on my LAN so I can read and write files to it. But I have no control of said machine, and as such, said machine frequently ...
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1answer
201 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 ...
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1answer
138 views

How are the different kernel naming schemes relate?

I am running Ubuntu 13.10 with the Kernel 3.8.0-030800-generic downloaded from http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.8-raring/ When I want to run for example turbostat or cpupower ...
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1answer
43 views

Is there any alternative to genext2fs in RHEL?

I am tryting to make initrd file system following [this tutorial][1] My host system is RHEL 6 64 bit. I am unable to get the required command: genext2fs No rpm is available for it, neither ...
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1answer
1k views

What would happen if the amount of free memory (vm.min_free_kbytes) was too low?

I came across the following parameter in kernel settings (in sysctl): vm.min_free_kbytes This is the amount of free memory (RAM) that's always free no matter what. In my case, I have only 1 GiB of ...
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1answer
77 views

Is there a way to permanently exclude the kernel from updates?

I'm using Fedora and wonder if there is some way I can exclude kernel updates when I run yum update, until I specifically want to update the kernel. The reason why I am concerned about this is ...
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1answer
293 views

Linux kernel: task vs thread

When I was reading a book(Linux kernel programming), I got interesting/confusing paragraph about mm_segment_t addr_limit(one of the member in struct_task) as below: mm_segment_t addr_limit; ...
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4answers
173 views

Why does *BSD uses driver specific names for network interfaces? Does it imply limitations?

I notice that depending on the brand of the network card, interface names differ (driver dependent I suppose). Why does *BSD uses driver specific names for network interfaces? Does it mean there is ...
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3answers
1k 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 ...
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1answer
76 views

OOM Killer value always one less than set

I am trying to set the oom_adj value for the out of memory killer, and each time I do (regardless of the process) I get back exactly one less than I set (at least for positive integers. I haven't ...
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4answers
443 views

Run command when temperature exceeds threshold, without daemon

I need to run a specific command if my laptop gets too hot (for example, send a STOP signal to Firefox or Virtualbox in order to prevent my laptop from shutting down violently and damaging my hard ...
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2answers
131 views

what is the difference between Device driver and kernel module

i know that driver is a software that can communicate with the hardware in order to control the device that attached to the computer.whereas kernel module is a small piece of code that can inserted ...
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1answer
72 views

filesystem that works under qemu and I can mount on my host

I'm using qemu for different kind of tasks, I would like to pick a filesystem that is both qemu-compatible and easy to mount under my host. I already discarded both qcow and qcow2 because apparently ...
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1answer
81 views

Getty instances in init process

Init typically will start multiple instances of "getty" which waits for console logins which spawn one's user shell process. Upon shutdown, init controls the sequence and processes for shutdown. The ...
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1answer
497 views

Kernel 3.12 or 3.10? which one has more features, newer and better?

Based on https://www.kernel.org/ kernel 3.12 is released in 2014-04-23 and kernel 3.10 is released in 2014-04-27. Based on release date, 3.12 is older and based on version number 3.10 is older. Which ...
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0answers
220 views

Some questions compiling linux kernel with make-kpkg

I'm doing my first steps compiling the linux kernel and adding a new system call. I've managed to do it, but I still have some questions. For this task, I has set up a Virtual Machine guesting debian ...
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1answer
62 views

Build kernel with multi_v7_defconfig setting

What is multi_v7_defconfig used for and how do I build the Linux kernel with this? I think I can write this into config file as: CONFIG_multi_v7_defconfig=y Please correct me if I'm wrong.
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1answer
285 views

set permission 0666 on /dev files at boot time

I have to load a few additionals modules. One of them generates /dev/knem file. I have to set the permission to 0666, so a basic chmod 0666 /dev/knem works, but I would like to assign it directly at ...
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1answer
895 views

kernel: disabling /dev/kmem and /dev/mem

I understand that /dev/kmem and /dev/mem provide access to the memory (i.e. raw RAM) of the system. I am also aware, that /dev/kmem can be completely disabled in kernel and that access can be ...
0
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1answer
232 views

How can I boot with a compressed rootfs?

My problem is: I cannot use compressed rootfs (the kernel crashes during boot) but uncompressed ones work fine. What I did: I'm using Buildroot 2013.11 to generate Images for my embedded Linux ...