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

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Installing kernel headers (prior to `make install_headers`)

I'm trying to accomplish this make ARCH=x86_64 INSTALL_HDR_PATH=/opt/cross/x86_64-linux headers_install But with the 2.6.9 kernel tarball. It does not support the make target headers_install and ...
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How to see kernel time variables without using adjtimex?

The man page for adjtimex says Anyone may print out the time variables, but only the superuser may change them. How do I see the value shown by adjtimex -p as the tick variable without using ...
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Debian boot freeze (hard lockup)

I'm using debian sid and during two years i watch the same problem. When I boot from grub my system on the screen appears follow text: Linux kernel in decompress level...Parsing elf and then freeze ...
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How do kernel inform OSPF daemon when a physical interface status is down?

When a physical interface status is changed from up to down, there are 3 things related to the computer's current routing table and OSPF. The (connected) network for that interface and remote ...
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Kernel config: Is undefined the same as disabled?

Reading the Debian Kernel Handbook I came across the config option CONFIG_DEBUG_INFO. That option isn't in the official debian 3.2 kernel config, so what I'd like to know: If a certain option is not ...
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Improve kernel boot time

I am using OMAPL138 and kernel version 2.6.37 and I would like to improve the boot time. By analyzing the kernel boot process I think it is taking a long time at MII PHY CONFIGURATION. The printscreen ...
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Debugging info in linux kernel - how does it work?

I have found that I can compile linux kernel with some flags adding debugging support like CONFIG_DEBUG_INFO. These options while useful in debugging are also required by some utilities like ...
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93 views

Why is Linux “Unix-like” if its kernel is monolithic?

As I understand it, part of the Unix identity is that it has a microkernel delegating work to highly modular file processes. So why is Linux still considered "Unix-Like" if it strays from this ...
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How to return 0 if a pattern is matched from a file? [duplicate]

I have a binary that repacks android kernel (not mkbootimg). I'm making a script to automate the process. I don't want any output on the screen. So I have redirected the output to a file named ...
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Can I masquerade a kernel uevent?

What I think happens From my understanding this is what happens when I connect a USB device to my computer: Kernel recognizes that I plugged in a USB device Kernel setups the very low-level things ...
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Boot process - Dev sdX name changes

I had a Slack 13.1 machine with 2.6.36 kernel. Then, I updated the kernel to 3.12.1. This machine has connected: a bootable disk with three partions (/dev/sda1 --> Linux OS files..., /dev/sda2 --> ...
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Install rtl8188etv/rtl8188eu driver on Orange-Pi

I'm trying to install the wifi driver on Orange-Pi board. The real chip is rtl8188etv but the driver is the same. I have compiled 3.4.105+ Kernel to have the headers: mkdir ...
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View syscalls/kernel activity for I/O from a running process

I'd like to be able to view syscalls or kernel activity for a process...I'm not actually sure of the terminology I need here! Specifically I'm looking for the difference between I/O going to local ...
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What is /proc/filesystems supposed to be and why is it different from /lib/modules/linux_ver/kernel/fs?

The very little documentation about /proc/filesystems says it is a "list of supported file systems". I see a lot of file system modules in /lib/modules/linux_ver/kernel/fs, most of which do not appear ...
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Missing kernel headers, but need them to install the Wifi driver

I am trying to install Kali on my Lenovo Yoga13, but after formatting the disk the setup failed to install grub because of no internet access (no Ethernet, need driver to get Wifi to work). So, I ...
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ubuntu Kernel panic while installing CentOS 7 in VirtualBox

I have a laptop with Xubuntu desktop 14.10 , and I installed VirtualBox and updated it to the latest version . I'm trying to install CentOS 7 (source downloaded from the official site) as a VM, ...
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What happens with functions using macro *__init* as prefix? [migrated]

From the info I've read about module initialization in a Linux OS, I came to know that the function calls that are having a prefix like __init will be placed in a single ELF location. For example we ...
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Cannot update new kernel for CentOS 7 although the server have space enough

I try to update kernel on my CentOS 7 but the yum say there is no space enough on /boot although /boot have 343 MB as show below: Filesystem Size Used Avail Use% Mounted on /dev/sda2 477M 105M 343M ...
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How to manually compile Fedora 20 kernel

I am trying to recreate an environment for debugging purposes. I require Fedora 20 specific kernel version (in this case its 3.17.7-200.fc20.x86_64). I have manually compiled vanilla kernel (3.17.7) ...
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Is it good to have multiple version of Linux Kernel?

Once, I was installing some kernel patches & something went wrong on a live server where we had hundreds of clients. Only one kernel was there in the system. So, the server was down for some time, ...
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57 views

bash runs out of memory

This question is a fork of this SO question. Here is the MCVE version: $ PS1='Parent-$ ' Parent-$ type seq seq is /usr/bin/seq Parent-$ bash $ PS1='Child-$ ' Child-$ for i in $(seq 1000000000); do ...
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Using DKMS, to automatically patch and install kernel on update

I have a system that needs patching a file in kernel to work properly. The system is running Ubuntu 14.04. The patch patches a file in drivers/hwmon. So after every kernel update I need to download ...
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Building a minimal linux

I have been following A Minimal Linux System from Scratch in order to build a Linux with a small footprint (10MB or less). I'm fairly certain that there were no errors up until the last point, where ...
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Avoid Booting Fedora in Failsafe Mode

I recently bought a Lenovo G50-45 and managed to setup a dual boot system with Windows 8.1 and Fedora 21 (UEFI booting). But when I boot Fedora, the following error message shows up: [1.079848] EFI: ...
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Linux Kernel Panic and Problem with boot

I have installed CentOS 6.4 on VmWare Workstation (Win 8 as Host OS). I worked with it for several days, but suddenly when I rebooted it, it did not boot properly and on stopped with this error : ...
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Doubt about kswapd reclaimation? [migrated]

In kswapd page reclamation flow what is difference between shrink_zone() and shrink_slab(), which pages are included in zone lruvec and shrinker_list. I want to know which pages are added in lurvec ...
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Investigating Active MemInfo

I am seeing high Active usage when I do a cat /proc/meminfo : MemTotal: 65965328 kB MemFree: 51640992 kB Buffers: 1050332 kB Cached: 8516112 kB SwapCached: 0 kB Active: 11512732 kB Inactive: 1878028 ...
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How to prevent kernel or any broadcast messages from flooding the TTYs?

Because of some hot-plugging issue, similar to what talked of here, the TTY displays show a continuous stream of messages (which are also logged in the /var/log directory). Every text I key in flows ...
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What is MCH_SSKPD warning in dmesg?

While i was reading dmesg log just to check that everything is fine, i met [ 18.956187] [drm] Wrong MCH_SSKPD value: 0x16040307 [ 18.956190] [drm] This can cause pipe underruns and display ...
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No brightness control for opensuse 13.2?

I have posted on brightness issue Here!! After upgrade to KDE 5 Now i cannot change brightness through controls !! AND ALL FUNCTION KEYS (wireless,brightness,touchpad,sound +/-) are not working ...
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Is it neccessary for me to update my kernel? And how? [closed]

I'm trying to install Kubuntu on a VM in order to do some deep learning following this guide: https://github.com/BVLC/caffe/wiki/Ubuntu-14.04-VirtualBox-VM I'm stuck in the step of the guide that ...
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nl80211 not found

Environment Linux 3.0.8 compiled for ARM FriendlyARM mini210s I cross-compiled iw for an ARM board (friendlyARM mini210s), when I installed the utility and ran it, I got this message: # iw --help ...
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How to properly build a minimal FreeBSD kernel?

Is there any proper way to build a minimal kernel for FreeBSD? The FreeBSD Handbook has the lack of information about this. By default /boot/kernel directory has the pretty big size - around 450MB. I ...
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Syslog message “rt_bind_peer(0) @ffffffffa0283f57”, twice in every second

My /var/log/syslog on a Debian server is flooded with lines similar to: Dec 23 16:05:40 server1 kernel: [ 686.957585] rt_bind_peer(0) @ffffffffa0283f57 These messages occur up to twice a second ...
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Does iptables protect from kernel vulnerabilities? [closed]

I read a lot of kernel vulnerabilities which are beyond my understanding. I would like to reduce the risk of an issue related to one. If I block everything other than SSH on a server, will this help ...
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Is the kernel version fixed within the life of a release/version of each Linux distribution?

I read the Table of versions of List of Ubuntu releases. I found that the kernel version for each release is fixed. E.g. the kernel is 2.6.24 for Ubuntu 8.04, 2.6.32 for 10.04, 3.2+ for 12.04, and ...
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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?
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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 ...
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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 ...
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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 ...
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116 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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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?