Questions tagged [kernel]

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

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How do proprietary work for majority of kernel distributions?

A question has been bugging my mind recently. Since virtually all proprietary modules are out of tree (and therefore not compiled against any kernel versions), I'm wondering how exactly they are ...
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building glibc for old kernel

I configured build with this command and built it using make Now I'm trying to create deb package with this settings but i failed with this error FATAL : kernel too old how can i do it?
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gc_thresh kernel config issues

We were having problems with kernel logs in our datacenter: arp_cache: neighbor table overflow! It was related to all of our servers having consul on them using gossip protocol and "flooding" the ...
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Rebuild a Centos kernel from a Debian netboot

I have (had) a Centos 7 system running on a server at OVH, booting from hard disk. I did a kernel update, and being in too much of a hurry rebooted just after it looked like all went well. It didn't. ...
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get errors after installing the netdata tool

after installing the netdata tool ( https://docs.netdata.cloud/packaging/installer/) we notice about the following errors that related to netdata tool [79103.083011] netdata[8026]: segfault at 2f ip ...
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How do I turn off a usb device completely by terminal?

My ThinkPad T480 running Linux has a fingerprint scanner that shows up to lsusb as Bus 001 Device 004: ID 06cb:009a Synaptics, Inc. There are no drivers for this fingerprint scanner, and according ...
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SysRq doesn't display any result on terminal

I use Mint 19.2, and I try to see CPU backtrace by the following process. $ sudo -s # sysctl -w kernel.sysrq=1 # echo l > /proc/sysrq-trigger But, nothing happened. I researched more ...
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kernel crash: rcu_sched detected stalls on CPUs/tasks and NMI watchdog: BUG: soft lockup - CPU stuck

I have a server crashing almost everyday. It runs on Debian, kernel 4.9.0-8-amd64. Here are the logs written before the latest crash: Aug 14 02:21:24 server6 kernel: INFO: rcu_sched detected stalls ...
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Partition being mounted as read only after copy operations despite healthy disks

I have an ext3 partition that is made from a logical volume. The volume group (8 TB) is made of 3 PVs (1* 4TB, 2* 2TB). The ext3 partition is the only partition from this volume group. I mount this ...
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mmcblk mounted as 1 -> root=UUID fail finding rootfs

I just upgraded Linux kernel (from 3.10 to 4.14), and now mmcblk rootfs partition as mmcblk1 (while in the older kernel in mmcblk0). I would have assumed that things should yet boot correctly from ...
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How to find the changes done to a particular kernel module through all releases

I need to access source code of all past versions of read_write.c under /fs/ from 3.10 to 5.3. So far I had to go through https://elixir.bootlin.com/ repeatedly and look at every single version that ...
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externally supported module, setting X kernel taint flag

Does this mean a driver is not from the original OS-distributor, the kernel becomes a tainted kernel? What does 'X' mean? I didn't see an explanation for 'x' ref: https://www.kernel.org/doc/html/v4....
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Understanding Linux process management [closed]

I try to understand the internals around the Linux kernel, the process management and the context switch around the processes. As far as I understand the tutorials (from this community, IBM, and so on)...
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Linux Mint 19.1->19.2 upgrade broke Cinnamon - driver issue?

Updating broke Cinnamon for me. I was on 19.1 Tessa, Cinnamon edition, and updated to 19.2 through the Update Manager. Now when I boot I get the message “Cinnamon just crashed. You are currently ...
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Timeout for function in the kernel

I'm trying to add a timeout for a c function in the kernel. I'd like to do something like the function try_until_timeout of the following pseudocode: void myfunction() {/* [...] */} void ...
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How does IPVS-NAT interact with iptables?

I'm using IPVS-NAT to do some load-balancing in Kubernetes (kube-proxy), I would like to understand when do IPVS's hooks get executed, I tried to read about this here: http://www.austintek.com/LVS/LVS-...
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Can't use ioctl() to control a device owned by kernel module?

I failed to use C/C++ to access the image sensor OV5645's register on my system via I2C bus. Below are some information about my system: Hardware: Dragonboard 410c + 96Boards MIPI Adapter with ...
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Context switch between kernel threads vs user threads

Copy pasted from [this] (https://www.tutorialspoint.com/operating_system/os_multi_threading) link: Thread switching does not require Kernel mode privileges. User level threads are fast to ...
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Why the rules I create in the iptables OUTPUT chain are deleted after a while?

I have a robot on local server that has the task of creating rules a number of times per day on remote server.The purpose of the robot is to calculate the traffic consumed by each port. Access to the ...
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How can I send dmesg printout to ftrace subsystem?

How can I send dmesg printout to ftrace subsystem? I like correlate the dmesg msg with the functions call graph in ftrace. Thanks
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How to disable iptables from kernel

I'm famillar with iptables -F and other features of iptables. I need to disable iptables from kernel, of course I prefer to disable from sysctl instead of recompiling the kernel.
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Weird major page fault number when reading sequentially / randomly in mmap region

I'm following this answer, trying to generate some major page faults with mmap: #include <fcntl.h> #include <stdio.h> #include <sys/mman.h> #include <sys/stat.h> int main(...
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How programs are broken into pages [closed]

Process are programs under execution and Operating system breaks these process into fixed sized pages. I want to know how OS breaks down the process into pages (at which stage)
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How to know why oom-killer triggerd and decode the oom-killer logs?

Below are the logs :- [ 727.941258] kworker/u8:2 invoked oom-killer: gfp_mask=0x15080c0(GFP_KERNEL_ACCOUNT|__GFP_ZERO), nodemask=(null), order=1, oom_score_adj=0 [ 727.954355] CPU: 0 PID: 56 Comm: ...
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CONFIG_EXT4_ENCRYPTION change in .config not persisting after building the kernel

I'm trying to enable encryption config in the kernel for Nvidia Jetson Nano(Tegra), by using menuconfig and rebuilding the kernel. But the specific change is not persisting and is overridden each time ...
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Fedora causes Thinkpad X1 Carbon Gen 7 to hang on reboot after “Restart and Upgrade”

I recently installed Fedora 30 on my Thinkpad X1 Carbon Gen 7. The installation went fine. On the first boot I went to the software center to check for updates. There were quite a few software and OS ...
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How to specify in kernel so that kernel doesn't use a range of physical address?

I am building kernel and I see that that in the system map there are certain addresses where Text Code is available. I don't want a range of physical address to be used by kernel. I want to do this ...
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How to change Kernel Base address when compiling Linux?

I am working on RedPitaya FPGA board and want to use Asymmetric MultiProcessing on it. CPU0 will be running Linux and CPU1 will be running Baremetal or freeRTOS. For that I need to change the Kernel ...
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Is a single big read/write request to the operating system less expensive than multiple small read/write requests?

According to the official documentation, one of the reasons why Java implements Buffered Streams is Most of the examples we've seen so far use unbuffered I/O. This means each read or write request ...
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Alternative of /sys/class/net/<iface>/addr_assign_type in older Kernel version

I have a scenario where I need to find out only physical MAC addresses (excluding virtual MAC addresses of docker container, AWS virtual MAC addresses, or any other virtual MAC address). To do this, ...
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Auditd, syslog and journald

I have been investigating about these 3 logging solutions, but still there are thing that unclear to me. According to the things i read, auditd audits events in the kernel and it has very deep and ...
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Accidently deleted kernels in the /boot directory and the computer will not boot

I've deleted some of my kernels in the /boot directory and saw that I've deleted the kernel that I was booting from by using the command 'uname -a'. Is there a way to change kernel in my grub.cfg so ...
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Booting a flat binary from USB

Following along with online resources, I've created a multiboot ELF file, but used objcopy to create a "flat" binary or data file. The kernel image is simple, only printing "hello world" to the ...
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Identifying physical network devices using /sys/class/net/<iface>

I wanted to know if there is a way to differentiate physical and virtual network devices. ip a doesn't have an option. So I am trying /sys/class/net/<iface>. There are 2 attributes ...
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Unknown display + no sound on upgrading kernel to 4.18 (Ubuntu 18.04)

I am running a Dell Optiplex 7060 with Ubuntu 18.04 (dual-booted with Windows). The system only has Intel's iGPU (UHD Graphics 630) to which I have two monitors connected, and it uses the Realtek ...
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Problem with booting — “Failed to start Load Kernel Modules”

When I try to boot Raspbian (Debian-based), I get [FAILED] Failed to start Load Kernel Modules. Additionally, my keyboard doesn't work (one of the "Kernel Modules" not loaded listens to the keyboard?)....
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Unmet dependencies 'apt --fix-broken install' doesnt help due to Kernel Upgrade

I have a VPS where I run my test programs on it and I tried to install python3.6 which requires libc6 and due to "Kernel must be upgraded" error I can't install anything anymore. I talked with the ...
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How to unmount device from a path hidden by another mounted device?

I have olddevice mounted to /mnt with: $ mount olddevice /mnt I would like to change the device at /mnt mount point. For this purpose, I simply mount newdevice on top of it: $ mount newdevice /mnt ...
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Is there any relationship between BIOS and Linux's Device Drivers layer?

We know Linux Kernel have: SCI, Kernel, and Device drivers. the Device drivers can communicate with the hardware. we also know BIOS is between the OS and the physical hardware. What's the ...
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'cat /sys/kernel/debug/pinctrl/INT*/pins' show not available

I want to do control over these GPIOs, but it shows those GPIOs are not available. ex: pin 4 (GBE0_SDP2) not available What's the problem? The possible driver source: https://github.com/torvalds/...
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acpi_themal_init takes long time during Linux kernel boot

dmesg | perl scripts/bootgraph.pl > boot.svg shows acpi_thermal_init taking up majority (80%) of kernel boot time. Furthermore, dmesg reports an unusually long delay between [2.947435] ACPI: ...
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Wrong display output due to kernel 5.0.0 issue (?)

I have got 2 monitors, and everything worked fine with Lubuntu where i had 4.4.0-31 low latency as kernel, just installed ubuntu 19 with its new 5.0.0-generic kernel and now the second monitor gets ...
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How to set a large stty size?(default 80x24)

I'm really not sure where is the problem, so I'm putting all message i think helpful here. dmesg | grep drm [ 0.316388] fb0: switching to cirrusdrmfb from EFI VGA [ 0.316769] [drm] fb mappable ...
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Is cached/buffered memory always instantly freed when an application requests it?

I have an ongoing discussion with the support of one of the cloud services. The problem is that we get "Cannot allocate memory" errors (for allocating shared memory segments by PostgreSQL) despite ...
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Compile linux kernel error

As a novice in linux kernel compilation, it's my first time to compile a Linux kernel for myself (I'm trying to use other TCP congestion control algorithms). I followed the steps in How to Compile a ...
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Linux Local Tables

Could you help me understand the practical use of the "local tables" ( versus the "main routing table"), displayed with command : ip route show table rt_eno2 My understanding of basic routing is that ...
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How to reset the terminal cache in the same session properly?

Currently, I am benchmarking the running time of a package from the terminal. When I use a command with the same file repeatedly, running time was much less than the first one, and this made me think ...
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What mechanism is used by Linux (or hardware) to ensure that any interrupt capable device does not cause too many interrupts?

At the level of interrupts, one would think that there has to some way for a maximum rate to be defined. Otherwise, a malicious device might be able to slow down the system, by continuously giving off ...
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How to fix broken Debian?

These errors (see pic. 1 and 2) appear every time I boot in Debian. I tried to update from stretch to buster, but it didn't have any effect. I have dual boot with Windows 10, so that potentially might ...
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Yocto Boot2Qt Build for Colibri iMX6ULL no wifi interface

I have built the linux distro Boot2Qt from source with the yocto tools for the board Colibri iMX6ULL which has the integrated wifi chip Marvell W8997-M1216. I installed the whole linux firmware-stack ...