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

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2
votes
2answers
33 views

Why is userspace slower than the kernel?

I've heard that FUSE-based filesystems are notoriously slow because they are implemented in a userspace program. What is it about userspace that is slower than the kernel?
1
vote
2answers
1k views

running kernel on QEMU

I face this message: Failed to execute /initKernel panic - not syncing: no init found. Try passing init=option to kernel. I am using this command line: qemu-system-x86_64 -hda disk.img -kernel ...
10
votes
3answers
10k views

How to disable USB autosuspend on kernel 3.7.10 or above?

I've updated my HTPC from kernel 3.7.10 to 3.10.7 and it seems CONFIG_USB_SUSPEND is now gone from the kernel options and included in PM. The main problem I'm facing is that I have an external HDD ...
4
votes
1answer
35 views

what's the difference between page cache and buffer cache?

In linux OS, you can type command "echo 3 > /proc/sys/vm/drop_cache" to release memory, and you can type command "sync" to release the memory. And in linux kernel there are two kind of cache, one is ...
1
vote
1answer
438 views

Why system call hooking produces different result everytime in Linux/Android 2.6.29?

I have implemented system call hooking for Android 2.6.29 kernel through a LKM module. I am tracing down one Android app for system calls. But interestingly, it returns different results every time I ...
0
votes
1answer
18 views

Custom Kernel to Disable SATA and USB Devices

I am setting up diskless clients that will run on an internal network. I have disabled SATA and USB ports using a BIOS locked with a password, but this is easy to get around by using the jumper to ...
3
votes
1answer
1k views

Kernel booting stops right after “Uncompressing Linux…”

I'm trying to bring up an ARM-based board. I've got U-Boot working but can't seem to get the kernel to load. Most of the time it only goes as far as: Starting kernel ... Uncompressing Linux... A ...
38
votes
1answer
45k views

How do you empty the buffers and cache on a Linux system?

Prior to doing some benchmarking work how would one free up the memory (RAM) that the Linux Kernel is consuming for its buffers and cache?
1
vote
2answers
47 views

Is system call the only way that a user program can intentionally affect the state of a Linux kernel?

I think there are several ways that a user program can intentionally affect the state of a Linux kernel. By invoking a system call; By invoking mmap() and writing the memory that has been mapped to ...
-2
votes
0answers
27 views

Unable to boot into kernel 3.18 [on hold]

I'm using VMware and Ubuntu 14.10. The kernel is successfully build and entered into the grub list but when trying to boot into it, it takes me to initramfs console.. I'm stuck...
2
votes
0answers
39 views

Can the hard drive timeout be disabled in Linux (attempting task abort)

Unfortunately, when a hard drive (usually a virtual drive) is slow, Linux aborts requests to that drive after a timeout, possibly causing data corruption. Last time this happened to me, I had 2 vms ...
0
votes
2answers
32 views

When building a new kernel in OpenBSD 5.6, can the name of `config` be something else?

I am using the release version of OpenBSD 5.6 and have to apply a patch called 004_kernexec.patch.sig (URL: http://ftp.openbsd.org/pub/OpenBSD/patches/5.6/common/004_kernexec.patch.sig ) An excerpt ...
0
votes
0answers
10 views

Looking for c-state syscalls (Kernel 3.10 [migrated]

Where can I find Linux Kernel 3.10 syscalls to manage C-State CPU Power Management?
-2
votes
0answers
28 views

Compile Kernel with Own Device Driver [closed]

Please tell how to compile kernel so as to add my own device drivers into a Kernel such that whenever one person installs/ Compiles this Kernel in their System, My Device drivers should be loaded ...
6
votes
1answer
147 views

Some basic questions about Linux kernel's security [closed]

I don't know much about Linux kernel, and I have some questions. What is the main purpose of separating kernel memory from user-space memory? To make sure that a user application cannot do anything ...
1
vote
1answer
91 views

iwlwifi: timeout delays firmware to be loaded

I'm using OpenSuSE 13.2 beta (which runs by the way very nicely). When starting up, my wireless adapter (Intel Centrino Ultimate-N 6300 AGN/Thinkpad T420) delays about one minute... But then it works ...
0
votes
0answers
21 views

different ways how Linux TCP/IP stack terminates connection

I have a Linux machine which connects to SSH server with SSH client(OpenSSH_4.1p1). SSH client machine has IP address 10.10.11.1 and SSH server has IP address 10.10.10.1. SSH client has kernel version ...
7
votes
2answers
6k 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 ...
1
vote
1answer
27 views

take the DRAM performance of the processes into consideration when scheduling

The CFS scheduler in Linux schedules the processes based on the virtual runtime of CPU. But, the DRAM memory is the bottleneck in most of the emerging domains. Why not take the DRAM performance of ...
0
votes
3answers
683 views

swap partition and its laws

I remember for choice of swap partition, we should use (swap > 2xRAM) at least.Of course it deprecated , because max of computer's ram is very high. kernel support it. My question: i remember each ...
0
votes
1answer
214 views

psmouse sync issues!

I have Compaq CQ61-420US (64-bit AMD) laptop with Synaptics touchpad checked using $ egrep -i 'synap' /proc/bus/input/devices N: Name="SynPS/2 Synaptics TouchPad" But recently after Arch Linux ...
0
votes
1answer
25 views

Disallow change of init kernel parameter

is there any way to disallow changing init parameter on boot time? I want to prevent situation when someone reboot my server, edit grub entry and get access without password. Maybe some kernel ...
5
votes
1answer
781 views

get kernel source code

I need a specific kernel version to compile it with some additional modules. When I typing: uname -r I get 3.8.0-29-generic I need this one. uname -a Linux "..." 3.8.0-29-generic ...
1
vote
0answers
4 views

Is inode_readahead_blks independent of read_ahead_kb?

I've been reading through the kernel documentation for block device sysfs tunables and I ran across the description for read_ahead_kb: Maximum number of kilobytes to read-ahead for filesystems on ...
2
votes
1answer
15 views

does the second kernel need kexec enabled

It's clear that you need the kexec syscalls in the 'first' kernel. But does the kernel that should get loaded (with kexec_load and reboot) need to be compiled with kexec? If yes, what extra code ...
35
votes
4answers
47k views

What is the difference between reboot , init 6 and shutdown -r now?

I just want to know difference between in reboot init 6 shutdown -r now and which is the safest and the best?
0
votes
0answers
12 views

linux vlan bridge feature backport to 2.6 kernels

The VLAN-aware bridge was introduced to the Linux mainline on the 3.x kernels, according to this article on lwn: VLAN filtering/VLAN aware bridge Has this feature been backported to the 2.x kernels ...
0
votes
1answer
2k views

bnx2: Can't load firmware file “bnx2/bnx2-mips-09-6.2.1b.fw”

I just compile the kernel 3.10.19 from kernel.org Support for bnx2 is enable. On my server when I try to start the eth0 interface I got the following error : bnx2: Can't load firmware file ...
6
votes
2answers
735 views

Asus X101H - Touchpad not recognized (want to disable while typing)

I have been struggling with this issue for a while and have done an exhaustive search for answers here and elsewhere before posting this question. On my Asus X101H, the touchpad is not recognized as ...
2
votes
2answers
955 views

busybox initramfs loop mount

I'm trying to loop mount my root filesystem (a loop file) within a busybox initramfs. I try to run the command: mount /rootfs.raw /root ... which works on my Ubuntu laptop, however, I simply get ...
0
votes
0answers
8 views

3.10.17 Kernel i2c buses missing on embeded system

On my ARM embeded system I have 4 i2c buses and only one shows up in /dev and in /sys/device/... folders. Other 3 i2c buses are not loaded. There is also no warning message inside dmesg, but there is ...
2
votes
1answer
337 views

Kernel headers for VMware tools

I tried to compile VMware tools on my server. I compiled the kernel myself, I didn't use RPM. As VMware tools needs the kernel header files, I executed the following command in my kernel folder ...
0
votes
1answer
24 views

BUG: scheduling while atomic

I have just installed Linux (OpenSUSE), and when start the OS, I get an error BUG: scheduling while atomic: systemd_udevd plymounthd... what does it mean?
2
votes
1answer
26 views

ifup wlan0 causes kernel Oops

on my laptop, when I do ifup wlan0, sometimes I get following call trace in dmesg. Other times, the log looks perfectly normal, and there are no kernel Oops messages. In both cases (with errors and ...
2
votes
1answer
1k views

SCTP support for Linux kernel 3.3.4-5.fc17.x86_64

I'm using Fedora 17 64-bit version, with Linux kernel version 3.3.4-5.fc17.x86_64. I installed lksctp using yum. sudo yum install lksctp-tools.x86_64 When I try to run sctp_status -H 127.0.0.1 ...
0
votes
0answers
13 views

Suspend Crash in android 4.4

During suspend clocks are not turning off, meanwhile when we resume clocks are not getting turning on. I am getting crash like <4>[ 216.945252] WARNING: at ...
3
votes
2answers
399 views

What does LTR kernel mean?

I was reading some sites and came across (LTR) by the number of kernel. Can somebody explain what is means?
0
votes
1answer
72 views

Cannot boot latest kernel update after installing on new system

I recently built my own computer, and I was excited to finally get to the installation of the operating system. I chose Fedora 20 to use as my primary operating system, and I was able to successfully ...
23
votes
5answers
8k 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 ...
2
votes
1answer
964 views

Scaling issues of i7 3520M with intel_pstate module on Kernel 3.10.0

Few days ago I updated my openSUSE 12.3 system from Kernel 3.9.8-1.gf3348a8-desktop to 3.10.0-1.g3dcd746-desktop and since then, turbo mode of my i7 3520M is enabled by default and it does not ...
0
votes
1answer
42 views

Is hardware helping reducing crashes of OS X? [closed]

I am taking an OS course this semester, and we mentioned that device drivers can cause about 85% of crashes(for Windows). My understanding is that: since many personal computers are configured with a ...
0
votes
1answer
1k views

Ping IP works, nslookup fails. New Kernel

I am compiling my own 3.14 kernel. I fear I may have left out some important networking feature to get DNS working. I can't resolve domain names. I can ping my DNS server. I can resolve using that ...
0
votes
1answer
22 views

cc1: warnings being treated as errors when compile FreeBSD 8.2 Release

I am trying to compile FreeBsd 8.2 RELEASE kernel # uname -a FreeBSD 8.2-RELEASE FreeBSD 8.2-RELEASE #2: Sun May 18 00:07:10 PDT 2014 Build the kernel # pwd /usr/src # make buildkernel ... it ...
23
votes
1answer
12k views

Kernel inotify watch limit reached

I'm currently facing a problem on a linux box where as root I have commands returning error because inotify watch limit has been reached. # tail -f /var/log/messages [...] tail: cannot watch ...
1
vote
1answer
26 views

Error compiling buildroot

I updated my buildroot for the version "2014.08" (stable version) and I updated the Kernel version (3.12.26) of my project, when the buildroot try to build the linux-headers-3.12.26 package, occurs ...
2
votes
1answer
373 views

Wireless constantly reconnecting on Ideapad running Arch

I just bought a new laptop, a Lenovo IdeaPad U330 touch, and after some struggle (with the Secure Boot stupidity) I have managed to install Arch Linux. I have configured my system, installed all the ...
4
votes
1answer
279 views

How to enable VESA framebuffer as default in NetBSD 6.1

When booting NetBSD, the old Tecra 720CDT that I have, works quite nicely in 1024x768x15 mode with vesa fb. I always have to activate VESA when booting the system: > vesa on > vesa 0x116 > ...
0
votes
0answers
43 views

CPU load and power management (frequency)

question background In my understanding the load value (shown e.g. by top) allows (together with the knowledge how many CPU cores the system has) a very quick assessment which share of the ...
0
votes
0answers
34 views

loading ath9k_htc kernel driver fails

could someone please point me in the right direction to get my external wireless stick (TL-WN722N) working on my Xperia Neo (haida) smartphone? So far I've done the following: I downloaded ...
18
votes
3answers
186 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 ...