The kernel of operating systems popularly known as Linux, or sometimes GNU/Linux.

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CentOS - acts abnormal every week and causes my whole setup to be down, how can I rollback / restore back to one week?

I have CentOS and Red hat enterprise Linux running, where I have now working Google Apps Engine and related other Python web applications. Every week or depending on any Google Apps Engine latest ...
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boot updated kernel image on beagleboard

Boot updated kernel image on beagleboard. I had installed a kernel on Beagle-board to update image of kernel to it. I've used this command: $ sudo apt-get install linux-image-3.2.0.49-omap It ...
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1answer
614 views

What are PCI quirks?

I hear a lot about PCI quirks when reading about the Linux kernel, but no website explains or defines PCI quirks. What are PCI quirks?
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How can I know if the current kernel was compiled with a certain option enabled?

Is there a way to know if the kernel was compiled with a certain option activated (i.e. CONFIG_PROC_EVENTS=y) without having to pull out the kernel sources package and looking in the config file?
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Will there be any security problem to permit non-root user set up a loopback devices?

if the user has full access to the image file (iso or disk image), will there be any security problem to permit him set up a loopback device backed by this file ? % ls -al /dev/loop* ...
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How to 'strace' a unix domain socket?

Kind of hard to explain but I noticed when straceing the PID that has the socket open I cannot see any of the communication. How can I sit in the middle of a socket file to watch communication?
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Allocated Memory difference in xen guests after using Linux 3+ kernel [closed]

Can someone explain to me why there is a memory difference in Guests with the same configuration? Hypervisor: xen 4.2 64 bit VM1: Centos 5.7 with 2.6.18-274.el5xen Assigned memory from xen is ...
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64 views

Significance of certain folders in linux kernel tree

While going through Linux Kernel Source tree, found certain folders, explanation of which was not seen in the popular sites. Could someone tell why these folders are there like: block - This is not ...
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configure allowed_tcp_congestion_control via config files in linux kernel

I am trying to come up with a custom set of TCP congestion control variants as part of the tcp_allowed_congestion_control. I do have multiple variants on my tcp_available_congestion_control list but ...
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2k views

Is “sync” before drop_caches necessary?

I have read a lot of docs saying, it is good idea to do a sync before doing echo [1,2,3] > /proc/sys/vm/drop_caches. I am not able to understand why it is needed, since drop_cache is a ...
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what is the linux boot param “memmap” equivalent in freebsd

In linux kernel, there is an option to reserve a portion of system ram i.e memmap=512M$2G (boot param) Here 512M starting from 2G would be reserved and not available to OS What is the equivalent in ...
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Resuming the Linux Kernel Configuration

I am configuring a Linux kernel before I compile the code. However, after I was thirty minutes into answering the many questions concerning various kernel settings, I accidentally pressed Ctrl+C. I do ...
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1answer
643 views

How to log iptables as of kernel 3.9.0?

What is the right way to log iptables as of kernel 3.9.0? I can no longer append a logging rule such as: # iptables --new-chain droplog # iptables --append droplog --jump LOG --log-level info ...
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223 views

After upgrading to linux kernel 3.9, kde does not start correctly

I recently upgrade my debian from kernel 3.2 to 3.9. This leads to a strange problem. After booting to kernel 3.9, it directly goes to tty7 instead of kde login. I can identify that kdm is up and ...
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What changed between kernels 3.7 and 3.9 that affects LVM/RAID root file systems?

I'm trying to fix a (very messy) system that the user hosed by running a kernel upgrade from 3.7.10 to 3.9.6. the root file system is on an LVM volume on top of a software RAID array. The boot manager ...
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Understanding the Buddy Allocator [closed]

I have a conceptual doubt in understanding the way Linux Kernel manages Free blocks. Here is what I interpreted through reading so far. The Buddy Allocator implementation is allocation scheme that ...
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1answer
91 views

How can I find the Secure Attention Key (SAK) on my system and can I disable it?

In answer to My process was killed but I cannot understand the kernel notice, I was pointed to some documentation on the Secure Attention Key (SAK) on Linux. I have a embedded system generated using ...
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get Various types of address used [closed]

How to get various address ranges of a running machine or a crash dump? User virtual address Physical address Bus address Kernel logical address Kernel virtual address I don't need the bus ...
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89 views

Download the Complete Linux Kernel Collection

I am wanting to download EVERY version of the Linux kernel as source code, Debian files, and RPM files. Where can I find a single site where I can download them all at once? If that is not possible, I ...
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How do I get a linux kernel patch set from the mailing list?

I don't subscribe to the linux-kernel mailing list, but I want to get a set of patches that were posted a few weeks ago and apply them to my kernel for testing. I'm very familiar with patching, ...
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1answer
142 views

What do the fields in the libata device probe line in dmesg mean?

When the kernel boots, it prints out lines like this for each SATA device: [ 0.919450] ata2.00: ATA-8: ST2000DM001-1CH164, CC24, max UDMA/133 [ 0.919487] ata2.00: 3907029168 sectors, multi 16: ...
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469 views

Enabling UTS Namespaces in the Linux Kernel

When configuring the Linux kernel, what are the advantages and disadvantages of enabling UTS namespaces? Would the new system be harmed if UTS namespaces were disabled?
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Understanding RCU when Configuring the Linux Kernel

I am configuring the Linux kernel version 3.9.4. I am being asked questions about RCU (seen below). Specifically, what are each of these and what are the advantages and disadvantages of enabling or ...
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How to set CONFIG_PREEMPT_NONE in RHEL 6.4 (linux)

I am trying to tune the RHEL6.4 Kernel to handle server style load for of my application. With RHEL 6 scheduler has been changed to CFS and with RHEL 5 my application works fine. I would like change ...
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mount options shown in /proc/mounts

IIRC then the mount options shown in /proc/mounts have changed. Some time ago acl and user_xattr were shown, now it seems that only noacl and nouser_xattr are shown if these features are turned off. ...
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Determine if reboot is required to update kernel?

I am running a server which runs on CentOS with cPanel (latest version) and I have it set to automatically update using yum. Since it needs to be rebooted in order to update the kernel (and possibly ...
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1answer
2k views

net.ipv4.conf.all.mc_forwarding: why is my access denied?

On Debian 12.04 LTS I am trying to access the key net.ipv4.conf.all.mc_forwarding by doing : sudo sysctl -w net.ipv4.conf.all.mc_forwarding=1 But every time I am doing this, I get the message ...
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how to get network QoS statistics in linux kernel?

Is there a way to get the bandwidth, delay, jitter collision, error rate and loss rate of a certain link through the interface on a local machine? let's say my machine is connected to a network via ...
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1answer
82 views

What are some of these directories in the Linux kernel src?

When I uncompress the Linux kernel source code from Kernel.org, there are many folders. I know what most of them contain and their purpose. However, I cannot figure out or find on the Internet the ...
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Can ps display only non kernel processes on Linux?

How can I ask ps to display only user processes and not kernel threads? See this question to see what I mean...
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53 views

Theoretical possibilities for cpu emulation built into boot-loader or kernel?

Is it a crazy idea to somehow make a blend of grub and qemu in order to boot linux kernels or any kernel of any cpu type supported by qemu or the built-in cpu? I know it might be impossible to detach ...
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Kernelpanic Fedora 18 with kernel 3.9.2-200

Since upgrading to kernel 3.9 I now get this error every time at start up: BUG: unable to handle kernel NULL pointer dereferences at (null) IP[<ffff8800ca93bfcd>] 0xffff8800ca93bfcc PGD 0 ...
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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 ...
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1answer
463 views

I'm failing to set up a wireless Access Point (AP)

I'm trying to get this card to be an access point, and am failing. I tried various Ubuntu releases, and checked on both ARM and i386. The kernel version I used is 2.6.35, and there is no Network ...
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obtaining kernel build tree

Could anyone explain me what the kernel build tree is? What files does it include? How can I obtain it from a cross-compiled kernel source (e.g. 3.4.0)?
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Can't install Linux Headers on Debian 6

I don't understand why this isn't working (I'm stumped!); root@box:/home/user# apt-get install linux-headers-2.6.32-5-686 Reading package lists... Done Building dependency tree Reading state ...
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File system CRC check

I know that before running the kernel, u-boot (the boot loader) will check the kernel image CRC. Only if it is correct it will go further, else it will give a "Bad CRC" error. I want to do same thing ...
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Linux snapshotting issues [duplicate]

Is there any way to deal with incoming writes while a backup is in progress in linux. Example, you are writing to your sql database and lvm snapshotting at the same time. This will result in corrupted ...
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1answer
187 views

compressed and uncompressed kernel on an embedded device

I have been using several different embedded boards that store kernel, init files, filesystem, etc. on partitions of a (micro)SD card. I notice in the example usage or instructions that compressed ...
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Why does Linux 3.2 kernel (Debian backport) hang during boot?

I wanted to upgrade the Linux kernel on my Debian wheezy (stable) on Thinkpad T60. I installed linux-image-3.2.0-0.bpo.4-686-pae, version 3.2.41-2~bpo60+1. The problem is it hangs during boot, just ...
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What does “INFO: task XXX blocked for more than 120 seconds” exactly mean on Linux?

I had this message in my kernel log : INFO: task XXX blocked for more than 120 seconds. I would like to know what it means technically: under what conditions does the kernel display this message about ...
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building/compiling kernel headers

I am compiling kernel 3.4 and 3.8 for different target devices. I would like to install compat wireless driver which requires kernel header. Could anyone tell me how I can compile/build the kernel ...
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Are FIFO, pipe & Unix domain socket the same thing in Linux kernel?

I heard that FIFOs are named pipes. And they have exactly the same semantics. On the other hand, I think Unix domain socket is quite similar to pipe (although I've never made use of it). So I wonder ...
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337 views

Real mode and loading linux kernel confusing

As far as know, protected mode will activated in kernel and in grub stage it still real mode. My misunderstanding is: In real mode, total memory available for use is less than 1MB but how grub can ...
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3answers
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files in /proc/$PID (e.g. ssh-agent, Chrome) are not owned by user but by root

I am just answering another question here :-) and thus had a look – wanted to have a look at /proc/$PID/fd of ssh-agent in order to find out which socket it uses. But I can't. I am quite surprised to ...
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What considerations need to be made when choosing the version of kernel for an embedded device?

I have used buildroot to successfully create a kernel, root file system and cross-compilers to enable me to write application code to run on an embedded device. Currently I have no need to write ...
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What is the relation between the Linux device drivers “domains”?

As I'm reading about the Linux device drivers and power management API I keep encountering terms like "system level", "subsystem", "platform", "class", and so on. What is the relation between them? ...
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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 ...
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865 views

How do you compile your own kernel on a RHEL6 system?

In RHEL6, the kernel is 2.6.32. What is the procedure to compile your own kernel?
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Does alsa depend on the kernel version?

Lately I had nothing but trouble with my sound setup. The full chain looks like this: alsa (pulse plugin)-> pulseaudio (jack plugin) -> jackd -> firewire soundcard This works fine, except ...