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

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“sync” before drop_caches,is it 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, drop_cache is a non-destructive ...
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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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103 views

Dom0 Xen kernel doesn't work with isolinux bootloader

I build my Dom0 kernel for Xen, but during boot, returns me the error: elf_xen_note_check: ERROR: Will only load images built for generic loader or Linux images I'm using isolinux because I need ...
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549 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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202 views

Wireless not detected in Linux Mint

I have updated my Linux Mint kernel from 3.2.0-23-generic to 3.8.0-23-generic, because the old kernel version freezes quite often. Now, I have a problem that my wireless network is not detected. ...
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197 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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115 views

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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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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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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119 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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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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752 views

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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140 views

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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692 views

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
65 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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Theoretical 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
387 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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111 views

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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657 views

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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276 views

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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138 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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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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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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49 views

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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500 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 ...
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616 views

How do I extract the filesystem image from vmlinux.bin?

jor1k ships a vmlinux.bin. I think there is an initrd inside, cause I don't know where else it would be. I am trying to extract the filesystem image so I can change it, but I don't know how to. I ...
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5answers
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Why isn't Linux embraced as the official GNU kernel?

While I knew for quite some time the existence of Hurd, and its mission as the official GNU Operating System kernel, I was wondering how come Linux is not embraced as the official GNU kernel over the ...
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258 views

Determine whether kernel built-in driver supports a device

I'm trying to find a way to accurately determine whether all the hardware on some system has a valid driver installed either via a kernel module or built-in to the kernel. I'm working with RHEL 5.5 ...
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Does linux modules/drivers belong to kernal space or user space

Some articles say that modules/drivers belong to kernel space as it take part in forming the kernel; (reference: http://www.freesoftwaremagazine.com/articles/drivers_linux) While others say that ...
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“Acpi-State” in slabtop's output gets increased — what is it? Is it a bug?

Since boot it gets increased occupying even more RAM than anything else: Active / Total Objects (% used) : 680608 / 719176 (94.6%) Active / Total Slabs (% used) : 17390 / 17390 (100.0%) ...
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How to determine which module taints the kernel?

My kernel keeps panicking when connected to a certain wireless network. I'd like to send a bug report but my kernel is apparently tainted. From /var/log/messages: Apr 17 21:28:22 Eiger kernel: ...
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How should I solicit feedback from a tree maintainer for patches sent to the lkml?

I have submitted a patch to the linux kernel that has gotten several reviews and gone through a couple iterations on the mailing list. It has been ACKed and reviewed by two developers, but they say ...