Questions tagged [linux-kernel]

The Linux kernel is the operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software.

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Windows equivalent of the linux kernel AnyIP feature

I have been leveraging the linux kernel's AnyIP feature to provide me with tens of thousands of addresses without the need to actually alias/assign those IPs and I was hoping the same feature has an ...
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Debugging kmalloc-64 slab allocations / memory leak

I have two virtual servers that are configured very similarly: Debian bullseye (testing), 5.6.0 kernel, 512 MB RAM. They're both running a similar workload: MySQL, PowerDNS, WireGuard, dnstools.ws ...
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Maxing Linux networking performance on multiqueue NIC

According to https://lwn.net/Articles/629155/ the Linux kernel, "can only forward something between 1M and 2M packets per core every second" - but how good Linux is at scaling across dozens of cores ...
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Systemwide File Access and System Call Monitoring on Linux?

In Windows land, you can run Procmon (Process Monitor) from Sysinternals, which will show you every File access, Registry Query etc Systemwide (screenshot attached). You can then backtrack to find ...
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which is the popular and linux distros for begginers [closed]

I want to install Linux but i know that it is not compatible with a lot of software and it is hard to use but it is good at security issues. so i would like your help for choosing the best distro as ...
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How does the linux kernel identify storage devices or any devices in general? [closed]

1 Problem: Today I encountered a strange behavior when trying to benchmark SSD's with a Raspberry PI and having two SSD's with the same label. 2 Setup: My setup is like this: My Raspi runs Ubuntu ...
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Update Ububtu 16.04 kernel

I try to update Ubuntu kernel from 2.x to 4.x. I download new kernel and unpack it but when I want to upgrade it with this command sudo update-grub I get this error. root@server:~/4.11.2# sudo update-...
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CentOS 8 keeps booting an old kernel

A CentOS 8 metal-bare server from OVH with a "boot from a local-disk" option enabled keeps booting an old kernel ignoring changes. I want to boot 4.18.0-147.8.1.el8_1.x86_64 kernel, and here is what I'...
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Kernel networking offload— flow/flower/flowtable offload

I am learning network hardware acceleration in Linux kernel for quiet a long time, but there still are several problems that make me very very confused. I hope to get anyone's help. Thanks very much. ...
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How to enable ECN marking in IP header in Linux

Is the ECN marking in the IP header is performed by default in Ubuntu (4.15.x kernel) or should the kernel be recompiled with a special option? I configured a RED ingress queue at an Ubuntu machine, ...
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Docker running on a amazonlinux:2 with an apache webserver returns 503 service unavailable

Setting up a docker container containing a apache webserver running on a linux OS. I am trying to setup a docker environment where i run an apache webserver at a amazonlinux:2 OS through docker. I am ...
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RTX 2070 + Fedora 31: nvidia_modeset error freezes computer just before login

I'm experimenting an error -which I'll describe next- with the following Linux system: Fedora 31 - kernel: 5.5.17-200.fc31.x86_64 GPU is ASUS RTX 2070 SUPER with drivers 440.82, also CUDA 10.1 and ...
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does RedHat EL6 uses systemd?

Does EL6 uses systemd? OS DETAILS here Linux version 2.6.32-642.11.1.el6.x86_64 (mockbuild@x86-027.build.eng.bos.redhat.com) (gcc version 4.4.7 20120313 (Red Hat 4.4.7-17) (GCC) ) SMP Wed Oct 26 10:...
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I have deleted /etc/rc.d/ dirs, how can I restore them?

I have accidentally deleted /etc/rc.d and /etc/rc0.d folders which resulted deletion of init.d and other related folders. 1.What is the use of /etc/rc.d, rc, rc.d, rc0.d, rc1.d, rc2.d.......rc6.d and ...
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grub/i386-pc/normal.mod not found centos 7

A CnetOS7 VM which is installed on top of ESXI is suddenly stopped booting and showing the screen as grub secure> I have tried the solution https://unix.stackexchange.com/questions/70538/grub-error-...
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Ping self IP address bypassing kernel

I wonder if there is a way to bypass kernel and redirect the ping packet to my network gateway when I ping my self IP address. For example, my private IP address is 172.31.42.99 and the gateway IP is ...
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Running kdump from kexec'd kernel

I am able to get kernel core dump using kdump with a normally booted kernel. I have a scenario where I load another kernel using kexec and want to get core dump after crashing the kexeced kernel. ...
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Committed/Allocated memory in Linux is less than used memory. How is that possible?

So I have a system with linux kernel 4.14.73 in which I am using values from /proc/meminfo in an program that shows the system specs including memory used and memory reserved. All was well until I saw ...
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How to tell how much memory is available to a single process in Linux?

I have a Linux server dedicated to Redis. Redis is supposed to take up almost all RAM to itself. I am worried that Linux may impose a limit on memory consumption for Redis. The question is this: how ...
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Ubuntu under Hyper-V: Which kernel to keep and how to get rid of the rest?

Recently I needed to quickly set up fresh new VM with Ubuntu 18.04 TLS under Hyper-V (this is not my ordinarily toolbox but I can not use anything that Hyper-V this time). Ok, I did the install (I ...
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How to disable Meltdown and Spectre patches in Centos 6?

I wondering how you can disable the Meltdown/Spectre patches in Centos 6? Various tutorials refers to Grub2 and recompiling, but in Centos 6, I do not have this. I can edit the grub.conf file in /...
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Linux - Netlink - is it possible to filter accepted commands/messages passing through netlink sockets?

Is there a way to apply a filter (some kind of firewall rules) to commands that can be passed through netlink ? I'd like to restrain the allowed commands to a very small subset of what netlink allows,...
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Linux pvmove gone awry after turning on mq_deadline, any way to recover?

So we had a migration in the office using pvmove. Then this happened Mar 8 12:26:51 v1 kernel: [ 5798.100321] BUG: kernel NULL pointer dereference, address: 0000000000000140 Mar 8 12:26:51 v1 ...
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Mount cgroup v1 instead of v2

Some context: I'm trying to get docker containers running under Linux Deploy under Android TV on an Odroid N2 arm64 SBC (kernel 4.9.113). I've got the kernel setup with the necessary bits for docker, ...
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Why is oom-killer truncating the name of a presumed offending file?

Here's an example log Jan 31 11:46:15 [kernel] [753684.206218] /usr/local/Calc cpuset=/ mems_allowed=0 Jan 31 11:46:15 [kernel] [753684.206244] CPU: 0 PID: 7577 Comm: /usr/local/Calc Tainted: P Now ...
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How can I tell which version of CIFs is in the kernel if CIFs module isn't loaded?

I need to determine the CIFs version that exists in my kernel, but the CIFs module isn't loaded. my-user@ip-XX-XX-XX-XX:~$ modinfo kernel/fs/cifs.ko modinfo: ERROR: Module kernel/fs/cifs.ko not found....
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How to disable IPv4 and enable only IPv6 on arm Linux target?

I am testing bind9 dns server for AAAA records. I would like to disable IPv4 to stop dns requests going to my default ipv4 dns server. In the resolv.conf i have added domain mydomain.com nameserver ...
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How to enable and disable IPv4 in linux system programmatically?

I am new to linux programming and based on some configuration parameter I want to disable and enable IPv4 on linux system programatically. The Pseudo-code of the solution would be like: if(...
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ClamAV for the host running docker containers - inotify/fanotify limits

I'm implementing anti-virus solution for Linux with ClamAV daemon running in On-Access mode, watching the created/opened files for malicious content at the host system AND in docker containers, ...
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Is there a way to have two versions of the same Adaptec RAID driver installed on RHEL 5 / CentOS 5?

We have an older Adaptec 5805 RAID controller on our CentOS 5 server. (I added RHEL 5 to the question because of the similarity in these Linux distributions.) An Adaptec 8805 controller was recently ...
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Commands to Upgrade Kernel on CentOS 7

My current kernel is 3.10.0-957.1.3.el7.x86_64. I got to know about this by using the command uname -r. Now I want to upgrade my kernel version to 3.10.0-1062.12.1.el7.x86_64. I used the below blog ...
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Debain 10 - Installing kernel 5 from backports

I tried to install kernel 5.x from backports in a frsh installed debian 10 and I failed because I have a 10G NIC: echo deb http://deb.debian.org/debian buster-backports main contrib non-free > /...
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Linux - ARM - page allocation failure:

I received the following error: ip: page allocation failure: order:10, mode:0x140c0c0(GFP_KERNEL|__GFP_COMP|__GFP_ZERO), nodemask=(null) . . . lowmem_reserve[]: 0 0 0 Normal: 1509*4kB (UEH) ...
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Nearly 100% disk utilization after upgrading to debian 10 without any reason

We recently upgraded our servers to debian 10. The setup is completely the same as with debian9 beside of course some new software packages. We are running the default kernel: $ uname -a Linux ...
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df -kh command in linux is showing 100% storage but df -i showing 18% storage why it is happening?

Output of df -kh [root@mavdu ~]# df -kh Filesystem Size Used Avail Use% Mounted on /dev/sda1 2.9G 2.9G 0 100% / devtmpfs 5.7G 0 5.7G 0% /dev tmpfs 7.7G 0 ...
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cgroup rt support in Debian Buster (Kernel 4.19.0)

Is it possible to enable the cgroup rt support in Debian Buster (kernel 4.19.0) without recompiling the kernel? Perhaps with a grub configuration parameter? Thanks. Background: Docker logs this ...
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Finding a system vulnerable to dirtycow

I'm not sure where to turn, so I turned to this forum. Please don't downvote me for nothing, I'm just trying to ask a question. Hello! So, I've been trying to find a system vulnerable to dirtycow and ...
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Ubuntu kernel boot arg `ip=` not honored; can't determine why

I have a machine with two network interfaces. See below (context) for setup... My boot params look like: set i ${net0/ip} set ns 192.168.99.101 set t tftp://${ns}/pxelinux.cfg set h http://$...
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Installed KVM but not recognised during virtual machine installation

I have installed qemu kvm in physical server with CentOS 7. The version is QEMU KVM 1.5.3. When I try to install CentOS in the virtual machine with the CentOS 7 iso, I get the following error. host ...
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Anyway to redirect 'page allocation failure: order:N' spew away from the “messages” file?

On big Linux systems running Centos, we sometimes see messages like kernel: <program_name>: page allocation failure: order:<N>, mode:0xNNNN Reading articles like these: https://utcc....
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Troubleshooting “kernel: NMI watchdog: BUG: soft lockup” errors

I recently faced issue with one of our AWS instances - which became sluggish for a while & later went to completely unresponsive state. Upon investigation I found following messages in the syslog....
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How to selectively disable IP reassembly?

The diagram below depicts a scenario that involves aggregation of three slow channel throughputs over a WAN. A fast host on a WAN (@ 54.239.98.8) is communicating with a host on a LAN (@ 192.168.0.100)...
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Fluctuating Throughput on Single Thread HTTP Connections (Nginx/Linux)

We are having some issues with fluctuating (unstable) throughput with a single stream HTTP download from an Nginx server on Linux. We find that a single HTTP thread produces unstable throughput with ...
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Sum of /proc/[pid]/status:VmSwap does not match /proc/meminfo (SwapTotal - SwapFree)

Issue: The sum of all the VmSwap entries inside of /proc/[pid]/status does not match the difference between SwapTotal and SwapFree. More details: I am noticing instances in which /proc/meminfo ...
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Can RHEL6 based kernel be upgraded with RHEL7 kernel version

To fix an issue with the kernel I need to upgrade it from 2.6.32.xxx.el6 to a 3.10.0.xxx.el7 but I am little skeptical because the version of Operating system is 6.10. Is it possible to upgrade new ...
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How to build kernel-debuginfo from available kernel

Problem: I have kernel(with iso) however that iso is not having kernel-debuginfo, I want to build build kernel-debuginfo to debug kernel issues. Any references will be appreciated.
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(105: No buffer space available) while connecting to upstream,

The server is returning 500 error. And in the logs I see many records like (105: No buffer space available) while connecting to upstream Tried to restart server : didn't help. Increased the number ...
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fatal error openssl/opensslv.h : No such file or directory

I'm trying to compile latest stable kernel version 5.2.13 on centos 7(kernel 3.10.0). In make bzImage step, I got following error. How can I sort it out?
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Unable to build initscripts package

I have some patches that I added in spec files and after adding those patches I am unable to build the rpm package. Obsoletes: hotplug <= 3:2004_09_23-10.1 Processing files: debugmode-9.03.61-1.0....
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How to configure auditd to collect logs from /proc kernel file directory

I've been looking for this for about 3 days now and have come up empty-handed. I am looking for a way to build a threat alert for Linux-based credential dumping in Splunk. To do this I need to be ...

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