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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Is it possible to upgrade from centos 6 kernel 2.6.32-754.25.1.el6.x86_64 to 5.12.1 version?

You are currently using centos6 kernel 2.6.32-754.25.1.el6.x86_64. I'd like to upgrade to 5.12.1 to take action against the vulnerability in this version, and I'm asking if it's possible. If it is ...
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Influence source address selection to same destination with multiple interfaces

I have a system with two network interfaces, both connecting to same default gateway. I want to load balance the connections to the same destination IP made from the system across both interfaces and ...
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How does linux know to mount / without /etc/fstab [migrated]

When /etc/fstab gets deleted/name is changed booting into the machine still works, in addition the root file system (/) is still mounted and on the correct storage device, how does it know to mount / ...
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What is the state of AppArmor network rules in the latest kernel?

I decided to give AppArmor a try and while it works great at restricting file access, signals handling etc., it completely ignores any network rules. It doesn't complain about anything, but it also ...
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What method can be used to resolve NMI backtrace for CPU 15?

An Xen Server virtual machine could not be pinging. View the interface of the machine from the Xen Server Console panel, as shown below: NMI backtrace for cpu 15 CPU: 15 PID: 114 Comm: kworker/15:1 ...
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What triggers a “*** Guest State ***” register dump from the linux kernel?

Prefix: There is no kernel crash. Something, rarely, is triggering Guest State, Host State, Control State register and other debug variable dump to kernel log. The system in question is running many ...
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Linux mountpoint can not be unmounted no matter what?

I have a mount point in Linux that does not show any open files in lsof or fuser. The mount point was exported in NFS, but is no longer exported, and there are no more files or directories in the ...
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kernel BUG at ./include/linux/skbuff.h:4470 leads Server to Hang

Server with linux version 5.5.0-050500-generic and OS version Ubuntu 20.04 LTS I have two interface which are connected to ovs bridge. As per normal flow packets are redirected to one interfcae to ...
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Linux header 4.9.0-11-amd64 is missing in debian

I am a software developer and have only a basic understanding about Linux systems. We are in a migration phase from GCP to AWS and found that the Linux headers are missing while installing Cloud ...
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Is “CPU MHz” from /proc/cpuinfo correct in Xen Dom0?

xenpm get-cpufreq-para indicates that I'm using the ondemand governor (set by cpufreq=xen:ondemand). The output also suggests that the CPU is running at 1.2GHz: scaling_avail_freq : 2000000 1600000 *...
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Erroneous inode values when disabling 64bit

Recently the NAS we use has been switched from 32bit to 64bit inodes on a nfs mount. Unfortunately we have legacy code which does not play nice with this. After some panicked googling I came across ...
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Scaleway's Arch Linux instance won't boot after system upgrade

Yesterday (February 22 2021), I started a new DEV-L instance on Scaleway with the Arch Linux image, after a full system update and a reboot, the machine is marked as "running" on the ...
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Linux no_console_suspend kernel parameter causes delay on resume from sleep

I'm facing no_console_suspend kernel parameter issue on my computer with Debian Bullseye (recent kernel 5.10.13-1). Normally, the computer wakes up from sleep immediatelly on the key press. But if I ...
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Does Cached includes Mapped pages in /proc/meminfo?

The Linux kernel definition for Cached memory does not mention it includes Shmem and Mapped pages (https://www.kernel.org/doc/Documentation/filesystems/proc.txt), but I've found some references where ...
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How to build kernel with OpenVZ support

Is it possible to compile 5.x kernel with OpenVZ? There is a full-blown custom OS built on top of RHEL6 called Virtuozzo 7.0, but it uses only 3.10 kernel. I would like to build any newer kernel, ...
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Network interface not working on CentOS: e1000 reset adapter

I have a physical computer running CentOS 7 kernel 3.10.0 with an Intel e1000 PCIe network card and a weird problem. 3 times out of 4, when i boot the machine the network interface isn't available and ...
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75% CPU wait and apt upgrade hanging

Recently I observed a relatively constant 7/8 (core) load on one of my servers. Looking with top, seems that CPU is constantly 75% waiting: Tasks: 401 total, 1 running, 400 sleeping, 0 stopped, ...
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How can I override IRQ affinity for NVME devices

I am trying to move all interrupts over to cores 0-3 to keep the rest of my cores free for high speed, low latency virtualization. I wrote a quick script to set IRQ affinity to 0-3: #!/bin/bash while ...
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how to triage linux disk IO system-wide “hang”

I have a box that is periodically "going out to lunch". Symptoms are anything requiring actual disk IO hang for 30+ seconds, and it appears anything already paged in is unaffected. The ...
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Multicast not received when socket is bind to bridge interface on linux

I have bridged eth0 and eth1 to br0 on a linux system. No other interface on the system, only one default route. I want to receive mutlicast traffic with a gstreamer udpsrc. When setting the interface ...
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watchdog: BUG: soft lockup - CPU#53 stuck for 22s! [kswapd4:543]

My Ubuntu 20.04 server has started complaining: [138070.784987] watchdog: BUG: soft lockup - CPU#53 stuck for 22s! [kswapd4:543] [138070.784999] Modules linked in: ufs qnx4 hfsplus hfs minix ntfs ...
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What is the purpose of /sys/block/sd?/device/rescan?

I need to "rescan" the SATA bus of our Linux server in search of a hotplug device that doesn't show up. I've seen an old question on the topic (How do I make Linux recognize a new SATA /dev/...
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How to get the latest kernel package on AWS EC2

I manage some EC2 instances running Amazon Linux (not sure what version), which need security patches. A lot of software was patched well, but we have stuck on the kernel upgrade. We are unable to use ...
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What is the difference between “Kernel messages” and “Messages from the init system and the system logger”

In this blog, it gives a Recommended serial kernel parameters, PCs with video card. console=tty0 console=ttyS0,9600n8 It says Kernel messages will appear on both the first virtual terminal and the ...
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confused about buff/cache and available memory metrics

I'm totally confused about the memory metrics provided by free command in linux. currently I receive the following metrics: total used free shared buff/cache ...
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Missing swap usage in OOM killer logs

From the following log, I understand that the swap is full and probably this is why the oom killer is invoked. But when I add the swapents column I can't even remotely explain how the swap is full. ...
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What is using (kernel) memory?

I know this kind of questions about memory usage have been asked several times, but unfortunately none seem to answer our current problem. We are currently running an AWS EC2 instance with the ...
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How to investigate TCP memory leak

We are running a medium size AWS EKS cluster (~120 kubelet nodes) running mostly Go services. The services deployed in the cluster are quite busy, handling millions of calls per hour. Each kubelet ...
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How do I get the Current time in milliSeconds in a Shell script in buildroot environment?

MYENV=$(date +"%s%N") printf "Time:: %s\n" "$MYENV" or MYENV1=$(date +"%T%N") printf "Time:: %s\n" "$MYENV1" I tried above methods, they ...
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Is BBR congestion control available on my host or not

I have been looking into enabling bbr congestion control on some of our servers to test if they make any difference for our workloads. We are on Amazon Linux 2: # uname -a Linux ip-10-1-66-180.us-east-...
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What contributes to memory “usage” in the OOM killer output in kernel 5.4

This is one of recent OOMs I've captured Nov 3 03:00:24 node kernel: [ 457.525768] memory: usage 98304kB, limit 98304kB, failcnt 0 Nov 3 03:00:24 node kernel: [ 457.525769] memory+swap: usage ...
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How to build kernel-debuginfo from upstream kernel

box: centos7.5 x86_64 from upstream: tar xvfz linux-4.xx.xx make menuconfig ( set CONFIG_DEBUG_INFO=y) save .config make rpm-pkg output 3 rpm:kernel-xxx, kernel-devel-xxx, src.rpm but where is ...
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pacemaker.log file is flooding with “Too many open files (24)”

My system is currently at Centos 8 and my /var/log/pacemaker/pacemaker.log file is flooding with GB of data and most of the error messages shows the below message. These messages are more than 1000 in ...
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Ubuntu Server 20.04 freeze/unresponsive, kernel BUG: Bad page state in process

Server Information: Distributor ID: Ubuntu Description: Ubuntu 20.04.1 LTS Release: 20.04 Codename: focal today I noticed my new Server crashed/froze. It did not accept any ssh ...
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Why is IPv6 disabled upon reboot even after configuring sysctl.conf?

First of all it cracks me up how many articles are out there to force IPv6 OFF on linux servers. Come on folks, get with the new! :D root@hodor:~# lsb_release -a No LSB modules are available. ...
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Why 224.0.0.1 traffic is filtered by Linux hosts?

When sending an ICMPv4 echo request to a destination address like 224.0.0.1, it is ignored by Linux hosts receiving the request. The destination MAC address used is 01:00:5e:00:00:01. The only way to ...
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Linux kernel version with (uname -r) does not show distribution version, where can I get the kernel source for this kernel?

I'm trying to compile a specific kernel module for my linux machine running on a hosted dedicated VPS. The VPS instance is running Ubuntu 20.04 64bit. In order to get the source code for the kernel I ...
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How to configure linux routing to enable load balance between two interfaces?

I have these interfaces on my linux machine : eth0, vti1 and vti2. vti1 and vti2 were added after I configured libreswan IPSec. Now I want to distribute traffic through both these interfaces equally. ...
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Enabling NUMA node in VM player custom Linux guest OS

I am trying to run DPDK helloworld example in a custom Linux distribution. I have installed custom Linux in a VMware player. The program is failed due to the fact the NUMA node is not supported. When ...
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How to list the capabilities associated with a process in *nix systems?

From - man capabilities UNIX implementations distinguish two categories of processes: privileged processes (whose effective user ID is 0, referred to as superuser or root), and unprivileged processes ...
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Why rules are not applied to the incoming traffic to limit bandwidth?

I have 3 PC2, two are clients and one server, which are connected through Ethernet. I'm trying to apply rules and filters to limit the bandwidth of the clients (ingress traffic) using the following ...
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Why is the size of read requests limited to 32 pages?

The FUSE man page says about max_read: With this option the maximum size of read operations can be set. The default is infinite. Note that the size of read requests is limited anyway to 32 pages (...
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How to load one physical CPU in a system with virtual cores?

I have an AMD processor with 4 physical cores and SMT enabled. Because of the latter, I see 8 virtual cores in a Linux box. For example, stress command can spawn a number of workers spinning on sqrt()....
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Need ubuntu 18.04.4 with 5.3 kernel, not 5.4

I had an 18.04.4 version of ubuntu that I recently upgraded, and lo and behold the kernel upgraded to 5.4, which is not what I wanted, as I have hardware that doesn't work on 5.4. I tried re-...
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What is Synology's RAID Technology based on?

I am curious about Synology's RAID Technology is based on which linux kernel modules. It seems MD+LVM according to its service center but I am not quite sure. Or the RAID function on filesystem is ...
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Why is the Linux kernel such an important/popular thing? Are there must-know things about it for day-to-day work? [closed]

DISCLAIMER: I have been a Windows guy for as long as I can remember, but I now slowly moving to Linux, Docker and Kubernetes (oh, boy!). On Windows I developed and administered commercial applications ...
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IPVS transmitting packets to incorrect backends

We are using ipvs for L4 loadbalancing which transmits packets to L7 backends on ipip tunnel mode. There are three ipvs systems configured with source hashing for persistence. Sometimes, ipvs is ...
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rsyslog: How to get imuxsock to read kernel messages?

Does anyone have any idea how to get imuxsock to read kernel messages? We have been having trouble getting any rule in an imuxsock ruleset to read kernel messages, in particular those from iptables. ...
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vmalloc allocation failure when scaling LXC containers past 1350 on Proxmox 6.2

I have a server of the following spec: Dual AMD EPYC 7742, 1TB RAM, 8TB SWAP (Round-robin 8xNVME array), 144TB SSD Storage (72 drives over 10 zpools) uname -a Linux host 5.4.44-1-pve #1 SMP PVE 5.4.44-...
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pcie SR-IOV driver howto

I am trying to know how linux PCIE NIC SR-IOV work. I am using a Unbuntu with Intel 82599 NIC as a host. Under NIC driver directory(ixgbe) in linux Kernel, there is a file named "ixgbe_sriov.c&...

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