Questions tagged [kernel]
In computing, the kernel is the main component of most computer operating systems; it is a bridge between applications and the actual data processing done at the hardware level. The kernel's responsibilities include managing the system's resources (the communication between hardware and software components).
862 questions
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How to debug ISO image loading via iPXE&HTTP?
In general, I'm trying to load the Ultimate Boot CD via HTTP (iPXE). The structure is as follows: CD ---\boot -------\grub -------\isolinux ---\pmagic -------\boot ------------\syslinux -------\...
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1 vote
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Building Kubernetes cluster lab on Incus system containers [closed]
I am trying to build a lab Kubernetes cluster in a Linux host, using Incus system containers as nodes. I want to do it in an automated way using Terraform and Ansible. The current status of the work ...
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1 vote
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57 views
High TCP retransmissions from RHEL 8.6 client (BBR) to RHEL 7.9 server (Cubic) during iperf3 test [closed]
We're testing TCP performance between a client and server using iperf3 in a controlled environment. Client: RHEL 8.6 with BBR congestion control enabled Server: RHEL 7.9 using default Cubic congestion ...
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0 votes
1 answer
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redhat + how to revert TCP BBR congestion changes
We have configured the BBR settings on all our RHEL 8.6 machines as follows: (according to Red Hat's documentation [https://access.redhat.com/solutions/3713681]). The goal is to assess whether the BBR ...
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Linux kernel cgroup v2 CFS - cpu throttled_usec accounting?
In Linux kernel cgroup v2’s CFS scheduler, how is cpu.stat throttled_usec accounted when a cgroup with multiple threads gets throttled during a single quota period? Specifically, is throttled_usec ...
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1 answer
182 views
Why is htop showing a lot of "kernel" activity?
Is it normal to see this much "kernel" activity on a server that is not currently running anything (at least at the user/application layer)? According to this link the red portion of the ...
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66 views
redhat + DELL + Controller reset is requested due to IO timeout
We have a DELL server with iDRAC (Integrated Dell Remote Access Controller). Usually, hardware problems related to controllers, storage, or disks are viewed through iDRAC. However, in our case, we see ...
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3 votes
2 answers
4k views
block nvme0n1: no uuid available providing old nguid - after disk cloning
On Rocky Linux 9.2 I made a copy of my full SSD with a software in order to replace the SSD, then I put just the new SSD in and booted from it, I seen a startup delay saying: A start job is running ...
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1 vote
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291 views
100% CPU on 4 of 8 cores on Oracle Linux [closed]
I have a desktop computer (Intel i4770) running Oracle Linux 7.9 with kernel 4.1.12-61. I usually keep it off and only turn it on on the rare occasions when I need to test something. A month or so ...
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319 views
Kernel crashing with `BUG: kernel NULL pointer dereference, address: 0000000000000020` after changing the GPU
After changing GPUs (both PCI-e NVidia) I started to experience frequent kernel crashes. Interestingly they happen in an USB module. The system runs Ubuntu 24.04.1 LTS. $ uname -a Linux pluto 6.8.0-48-...
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Linux kernel prroblem with RAID: megaraid_sas 0000:43:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x000e address=0xa518d000 flags=0x0020]
After upgrating Proxmox from 7.2 to 8.2 and Linux kernel from 5.x to 6.8.4-2-pve (Proxmox) I have problems with kernel module megaraid_sas for AVAGO MegaRAID SAS 9440-8i controller. Server starts but ...
0 votes
1 answer
780 views
Update of kernel on Ubuntu never succeeds
A couple of our servers do not upgrade the kernel when prompted. The following message prompt occurs: Kernel Upgrade Kernel Upgrade Restart After closing and restarting the services, nothing has been ...
0 votes
1 answer
86 views
ALIX with OpenWRT keeps restarting
I've got problem with ALIX 2D3 (or 2D13) which keeps restarting. It reboots in different period of time - from 2 to every 20 minutes. What we did is changed DC adapter but it's still looks the same. ...
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2 votes
0 answers
449 views
How useful is ionice tool with modern linux kernel
Ionice tool is supposed to offer relieve on high I/O load by executing commands only when system is in specified state. https://www.linux.org/docs/man1/ionice.html states Linux supports I/O ...
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0 votes
1 answer
1k views
Debian: revert kernel installation from backports
I was running Bullseye (Debian 11?), tried to install kernel 6.x from the bullseye-backports. I am really not sure how to undo it. The new kernel does not work with the graphics driver and a few more. ...
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1 vote
0 answers
824 views
Linux Driver CH341 USB Adapter Serial Port issue
On a x86_64 miniPC, a led strip can be controlled sending some bytes on a serial port. This control works on Windows but fails on Linux. On Windows, these lines in PowerShell switch the led strip off: ...
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0 votes
1 answer
43 views
RateLimit is doing weird maths and wrong numbers on kernel
I'm trying to apply a set of rate limit within iptables, and it's doing some weird maths that i'm not able to see on the kernel why this is happen. I tried to execute same code on my local machine, ...
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19 votes
2 answers
3k views
What could explain unknown I/O on new 16TB HDD on a Debian server?
I recently obtained a new 16TB HDD for my Debian server. I first created a partition (gpt) on it via my Ubuntu-like desktop, formatted it (ext4), and rsync'ed old data on it. The disk is now usable, ...
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0 votes
0 answers
79 views
Kernel TLS Socket Redirect
Suppose both the client as well as the server are on the same machine and they want to do mTLS. They both choose to offload the TLS to Kernel (kTLS). Now when the key exchange happens, given the ...
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1 vote
0 answers
131 views
IMSM (Intel Matrix Storage Manager) device is not detected by Linux kernels 6.6.x/6.7.x but works in 5.19.17
In kernels 6.x.x /dev/md/imsm0 does not appear at boot. The only difference I see in dmesg which seems to be relevant: block device autoloading is deprecated and will be removed. Printed in 5.x.x, ...
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2 votes
1 answer
3k views
RHEL + how to prevent OS disk - sda to change after reboot
We installed RHEL 7.9 version on physical machine., when sda device was the OS. The machine has the following disks. sda - OS disk sdb - data disk sdc - data disk After reboot OS disk device changed ...
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4 votes
0 answers
259 views
Write speed to NVME disk degrade after some time of active work
I have a fairly general question, but maybe someone already had similar behavior. I have few servers with 20 nvme micron 7450 pro 15 TB disks on each. On all servers I created raid 0 using mdadm ...
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0 votes
1 answer
278 views
Amazon linux 2 - two kernels enabled
I recently upgraded kernel on one of the servers and I have two kernels enabled after reboot: # amazon-linux-extras |grep kernel _ kernel-5.4 available [ =stable ] 55 kernel-5.10=...
1 vote
1 answer
397 views
servers unusable after boot...piix4_smbus SMBus Host Controller has stopped loading during boot, Debian Testing, various kernels
We have multiple old (14+ years) Tyan S3950 mobo servers running debian Unstable with various recent kernels like 6.1.0-3-amd64. Despite being on the bleeding edge with the unstable distro, this has ...
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63 views
Cannot configure VirtualBox because correct kernel RPMs cannot be found
I'm trying to configure VirtualBox on my CentOS 7.9 server. However, my kernel version is 3.10.0-1160.99.1.el7.x86_64, and I cannot find kernel-devel-3.10.0-1160.99.1.el7.x86_64.rpm or kernel-headers-...
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3 votes
0 answers
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Cannot "apt upgrade" due initramfs error - "update-initramfs: failed for /boot/initrd.img-5.15.0-86-generic with 1."
I have a Ubuntu 22.04 VM with CloudInit on a Proxmox Host which worked well, but recently I got often the issue after some time (some days, even after reinstalling) that I can't upgrade packages due ...
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1 vote
1 answer
3k views
Enable BTRFS in kernel (running Rocky Linux 9.2)
I am trying to read an encrypted filesystem pulled from a Fedora 38 installation on Rocky Linux 9.2. When I plug the SSD in, it shows the following error: I suppose that this means (1) the default ...
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0 votes
1 answer
1k views
I want to make Linux Kernel Source an RPM file
I am currently using Rocky Linux 8.7. The current kernel version is "4.18.0-425.13.1.el8_7.x86_64". I want to upgrade kernel through RPM, not source compile. In the kernel compile step, use ...
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1 vote
0 answers
369 views
Automatic TCP SYN - cookie activation
I am simulating a SYN flood attack on a Raspberry Pi 1 with KALI Linux (ARM) installed. A similar message as mentioned in this post was printed after performing the attack: How to avoid syn cookies. ...
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808 views
EXT4-fs error (device md0) in ext4_free_inode:357: Filesystem failed CRC
After setting up Raid1 Mirror on DNS server, now I am planning to go for a Debian upgrade from 10 to 11. I was able to update the source.list file and perform apt update but when i do apt full-upgrade ...
0 votes
1 answer
578 views
Why MACsec can not reach more than 2Gbits/s?
i am configuring macsec and i have discovered that, when using this protocol to send/received data, the bitrate is so low. I am using it over a 10Gb network adaptor, using iperf3 it almost reach that ...
5 votes
3 answers
6k views
What are the options to monitoring page cache usage?
In essence the Page Cache is a part of Virtual File System (VFS) which main purpose, as you can guess, is improving IO latency of read and write operations. In computing, a page cache, sometimes also ...
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1 vote
1 answer
570 views
ZFS I/O Error, Kernel Panic during import
I'm running a raidz1-0 (RAID5) setup with 4 data 2TB SSDs. During midnight, somehow 2 of my data disks experience some I/O error (from /var/log/messages). When I investigated in the morning, the zpool ...
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0 answers
221 views
Number of receiving queues is double the number of cores of my server?
I'm using Mellanox ConnectX-5 100 GB NIC, Linux kernel 5.15 and my server has 32 cores (SMT disabled). But in the /sys/net//queues, the number of rx queues is 64, which is double the number of cores ...
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2 votes
1 answer
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Can we use fdisk to partition a disk bigger than 2 TB without recompiling the kernel?
Here is my problem. Our operating system is Debian 11. The main hard disk is doing fine. I have a 6TB external volume. If I choose to use parted to format this disk it will entail recompiling the ...
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1 vote
0 answers
106 views
Saving contents of /proc/net
I'm trying to archive files from /proc/net when a process crashes. This is to aid in debugging, to get understanding about the machine status when crash happened. The contents are not regular files, ...
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0 votes
1 answer
550 views
kernel messages are complained about memory.inspite all DIMM cards was replaced
we have few DELL machines ( with RHEL 7.6) , and as we replaced the DIMM cards on machines because the Erros that we seen from kernel messages after some time we checked again the kernel messages and ...
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1 vote
2 answers
376 views
iSCSI shared disks with custom device name on clients
I'm using RHEL 7.9 (Maipo) and need to setup for all iSCSI clients the same device name, like /dev/sdb or /dev/thiscustomname. I could do that by sharing the source disk using multipath, but for Db2 ...
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1 vote
1 answer
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RHEL + how to capture fresh kernel message without machine reboot
here is example from dmesg output from important production server ( RHEL 7.2 - DELL machine HW ) as we can see the sde disk in server is dying [Wed Jun 30 11:24:58 2021] sd 0:2:4:0: [sde] tag#0 ...
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0 votes
0 answers
315 views
SLURM / NFS based computing cluster with disk uniterruptible sleep issues (state : D)
Context : We have a computing cluster based on 7 servers, running Debian 11: a storage (HDD NAS, ~500TB, RAID5, LVM) a frontal server, running SLURM, nfs-common 5 nodes on which the storage is ...
1 vote
0 answers
738 views
cat /proc/pid/cmdline hangs (no cgroups, no nfs or network fs, no memory issues)
We are a bit stumped. Once in a while ps/w hang forever (at least an hour) on our server, and it is on reading /proc/pid/cmdline for a process (happend twice today, verified with strace cat directly ...
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1 vote
0 answers
353 views
RHEL server + what is the meaning of the kernel messages about Hung TX queue XX
We have 524 RHEL machines. in our Hadoop cluster ( all machines are DELL HW ) all machines are RHEL 7.2 version (old kernel version) uname -r 3.10.0-327.el7.x86_64 last week we seen the following ...
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0 votes
1 answer
874 views
Why do some servers have /etc/sysconfig/kernel and others do not?
I spent some time looking into this and couldn't figure out why there are servers with and without /etc/sysconfig/kernel. What's particularly interesting is that we have some servers with the same ...
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0 votes
1 answer
849 views
Clear RAM Memory Cache and buffer on production Hadoop cluster with HDFS filesystem
we have Hadoop cluster with 265 Linux RHEL machines. from total 265 machines, we have 230 data nodes machines with HDFS filesystem. total memory on each data-node is 128G and we run many spark ...
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1 vote
1 answer
2k views
Linux server loses network connectivity after an OOM event
We have a server runnnig Linux 5.15 and we've had multiple verified situations where a process is killed by OOM and that leaves the whole system inaccessible on the network, both for inbound and ...
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0 votes
1 answer
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kernel message + how to know if we need to replace the DIMM based on kernel messages
we have RHEL 7.6 server , and we noticed about the following kernel messages. [1065085.048872] EDAC sbridge MC0: PROCESSOR 0:406f1 TIME 1676989040 SOCKET 0 APIC 0 [1065086.052107] EDAC MC1: 0 CE ...
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3 votes
0 answers
6k views
Explain of OOM killer logs
I have a question about the OOM killer logs. We are expecting a lot of OOM kills. The ecosystem My ecosystem looks like below: I have a server with 4 cores and 8 GB of RAM. I am running there the ...
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0 votes
1 answer
460 views
Is the outgoing connection from a OpenVPN client to a LAN behind an OpenVPN server forwarded by the server kernel?
I've observed a somewhat strange behavior that I can't quite understand. So I set up an OpenVPN connection as shown in the graphic below. (It's a TUN and client-to-client setup). My thoughts are ...
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2 votes
1 answer
1k views
Fix kernel issues in rescue mode
I have updated the kernel in a VPS Centos 7, and after rebooting, the machine is not responding anymore, including with SSH. I connected to the VPS via a temporary rescue linux machine from where I ...
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3 votes
0 answers
301 views
How to tell whether a linux tcp socket had recent activity?
Most of the time, when changing or upgrading a network service, I would do this during maintenance hours but some services are rarely used so it is tempting to just check whether it is currently in ...
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