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 ...

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How to disable perf subsystem in Linux kernel?

I'm running some benchmarks. My benchmark runner monitors the dmesg buffer between experiments, looking for anything which could impact performance. Today it threw this up: [2015-08-17 10:20:14 ...
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47 views

What are sensible semaphore numbers?

What are semaphores and how are they caused? has a fairly good explanation of what semaphores are, but I'm not sure what my configuration should be. I recently ran into the same problem as that ...
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131 views

Upgrading kernel on Debian server hosting Xen 3.2.1

I have a physical server running Debian 6 and Xen Hypervisor 3.2.1, and kernal -a says "2.6.26-1-xen-amd64". I have not updated for a long time, because when I run apt-get upgrade, one of the updates ...
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423 views

detecting whether GPUs are accessible before running nvidia-smi during boot to create dev files

In the past, I've successfully configured Ubuntu systems containing NVIDIA GPUs to launch nvidia-smi in the background from within /etc/rc.local during the system boot to create the requisite /dev/...
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53 views

how to read the results about packet drops from crash tool

I have Linux machine red hat 7.2 because the dropping problem on eth1 interface we perform the test according to red hat link - https://access.redhat.com/solutions/206223 finally we get the ...
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37 views

How to reliably capture Linux kernel log messages in case of a system debilitating crash (BUG, panic)?

I'd like to have access to the lines/tracebacks/whatever whispered by the kernel right before dying. This has proven problematic, because all interfaces I have access to become disabled. Post-reboot, ...
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237 views

BUG message on xenserver 6.5 - bad memory?

Several times a day I receive the following error in /var/log/messages. The server hangs and requires a reboot to respond again: Feb 1 13:44:54 xenserver-abfuqvrs kernel: [35023.166776] BUG: unable ...
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1k views

OpenVPN ERROR: could not insert 'tun': Unknown symbol in module, or unknown parameter (see dmesg)

I'm trying to configure OpenVPN on my Debian 7 VPN but I'm getting the following error ERROR: could not insert 'tun': Unknown symbol in module, or unknown parameter (see dmesg) I tried the ...
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33 views

Process identifier mask in z/OS

I've noticed a curious pattern to process identifier numbers on the z/OS system I'm working on (uname reports it as OS/390), they're either 1-4 digits long or 8 digits long but never in between. The ...
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239 views

Redhat 6.4 configured to log Martian packets but is not logging ll header

I am trying to investigate the source of martian packets I have been seeing on several servers connected to the same subnet. The logging of martian packets has been enabled in /etc/sysctl.conf. ...
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418 views

CentOS 6 won't load default (new) kernel, loads (another) older one instead

I am having a weird issue with a CentOS 6 system. I have upgraded the kernel twice now and when I reboot the system it still loads the older kernel. I also had a dc tech watch the screen as it ...
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953 views

“sched: RT throttling activated” KVM host - what does this mean?

Ubuntu 12.04 64bit - under a KVM parent. 32 cores. So we seem to be having some load issues. We have noticed this line in kern.log: "kernel: sched: RT throttling activated" What does this mean? Is the ...
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70 views

Kernel fails to assign memory in any Linux Distro

I have a motherboard: X11SBA-LN4F/F. After install CentOS, i have error in log: May 2 21:47:48 ll-226 kernel: pci 0000:04:04.0: BAR 14: failed to assign [mem size 0x00200000] May 2 21:47:48 ll-226 ...
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18 views

BSOD BugCheck on Multi-core system - What thread caused the crash?

I am aware that a Windows' system will crash with a stop error and "blue screen" for a few common reasons, some of which may be: A device driver or OS function that runs in kernel-mode space ...
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25 views

How can I track security issues with running kernel under paravirtualisation?

I've got a bunch of client's virtual machines running by various providers who use Xen paravirtualisation. Almost all of these are Debian or Debian based systems. I rely on APT pretty heavily to ...
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0answers
28 views

Weird network interrupt issue

in ifconfig output i am seeing Interrupt 16 but when i check in /proc/irq/ i am not seeing number 16 there. following number i am seeing here. my driver is broadcom tg3 [root@centos7 ~]# ls /proc/...
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61 views

VIA south bridge puts CPU to sleep, disables timer and ethernet interrupts

I have two VIA NAB-7410 boards with 4x Intel 82541GI gigabit adapters. On both boards, Linux occasionally stops responding to Ethernet frames. The problem goes away when another interrupt is triggered,...
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204 views

Ubuntu server 14.04 postgres Tainted

I run an Ubuntu 14.04 server, on which Postgresql 9.3 is installed. I am seeing kernel messages flooding kern.log and syslog, hundreds of lines a minute, until the server is out of free space. I'm at ...
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50 views

/proc/stat btime value change after boot

In a Linux server with the kernel 3.16, not virtualized, but with the ntp daemon active, the variable "btime" wich gives the time at which the system booted, change a few seconds before booting. For ...
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0answers
81 views

slabtop command doesn't work

I've inherited Sys Admin duties on webserver and I'm a bit of out my element, but learning as I go. My newest issue is all the of the ram has been gobbled up and I'm not sure where it has gone. free -...
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30 views

DRBD device temporarily disappearing across different kernel versions?

After upgrading from an old kernel to a new kernel version and booting into the new kernel the DRBD logical device was gone. Think nothing under /proc/drbd. This is a major problem as I have DRBD ...
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0answers
113 views

Kernel panic under DDOS

I'm running a Debian 6 - 64bit system (Kernel 2.6.32-5-amd64) and often get flooded with DDOS. I have tuned the network parameters under /etc/sysctl.conf to not let any kernel parameter overflow. ...
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0answers
50 views

Broadcast ARP weirdness

we a running a router on a custom Linux box. Kernel is 3.14.14. What happens is that when you arping the router in broadcast only mode is the router has a verey slow response time: # arping -b -c ...
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181 views

Verify architecture of kernel file

Note: I am NOT interested in the currently running kernel, but on a kernel that I am going to boot and which is in a file in the filesystem. I am going to boot a new kernel. I have prepared grub.conf ...
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0answers
665 views

OpenVZ - updating kernel and all containers

Last night I upgraded to the latest kernel of openvz. I rebooted the host node. It came up with the latest kernel. However, the containers are still running the old kernel. What I did on the host ...
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365 views

collect previous kernel logs in linux after reboot

how to collect previous kernel logs in linux after reboot and how to search the old logs? Initially when system is rebooted the logs are not captured and found rest of the log's.But there is an error ...
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0answers
200 views

Linux kernel module “Unknown parameter” stops module from loading. How to load module anyway?

The following is happening on a Ubuntu 10.04 system I'm working on: The kernel is shipped with e1000 driver module version 7.3.21-k5-NAPI. This version of the module is causing problems. To fix, the ...
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372 views

demonstrate Automatic Hardware Clock Synchronization By the Kernel (11 minute mode) without ntpd

From the man page of hwclock: This mode (we'll call it "11 minute mode") is off until something turns it on. The ntp daemon xntpd is one thing that turns it on. You can Ok, I have a ...
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0answers
218 views

iptables xt_recent change in kernel without modules

is it possible to change xt_recent module parameters when it is compiled into kernel ? most of the info on internet suggest setting it by modprobe but that is not the case in my setup as I have ...
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0answers
289 views

FreeBSD XEN kernel not booting in XenServer 6.2

I have a XenServer 6.2 host, and I am trying to get a FreeBSD-9.1-i386 guest to run in PV mode. The installation of the guest is fine, but after a reboot with the new kernel the system does not boot. ...
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0answers
578 views

Xen hangs on boot when scrubbing RAM

I have a CentOS 5 server I can boot into the stock kernel just fine, but when I try kernel-xen, it gets stuck here: When I try adding no-bootscrub to the kernel command line, I get this and a ...
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406 views

UDP socket receive buffer size change on RHEL6.3

Our system used to work on RHEL5.3 And the socket receive buffer size is 64k. And that works fine. We can get message size up to 64k on UDP socket. But after system upgrade, it is running on RHEL6.3 ...
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0answers
234 views

what does setting kernel.shmall too high do?

I'd like to know what the kernel does when the value of kernel.shmall works out to being larger than the total amount of available memory (main memory + swap space). Is the value ignored and the ...
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0answers
304 views

Ubuntu - random reboot since 3.0 kernel

I have an Ubuntu Server that is now upgraded to 12.04 LTS server. Ever since I've upgraded from 10.10 to 11.04, when the kernel went from 2.6.38 to 3.0.anything, my machine would constantly randomly ...
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0answers
189 views

Find counts of ulimit quotas

So, we may have some sort of zainy leak in our software. We're using Mono and spawning many processes over the course of weeks/months. Eventually, we can't spawn anymore on our clients machines. It ...
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0answers
418 views

Does TIME_WAIT affect dynamic ports?

I've read a bit about TIME_WAIT connections, and know they should be harmless to my server (connection closed, so no resource connected with this socket). Recently, my server reached the magic ...
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0answers
159 views

Would OOM_Killer succeed if SIGKILL didn't?

Last week an user application turns out to hog one of my servers. It was exhausting the memory gradually and slowly. When I attempted to kill -9 PID the PID went in state D. While this was eating the ...
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27 views

Server hangs with the following messages and on reboot starts to check file system automatically?

these were the messages on the system when i took the drac die+8be/8x98 dOithp+8XC4/8X168 dOidiUidEiEPPOP+8X8f/8Xb8 findibusiestigroup+8xSC5/8Xb28 tcpiestablishediopti0n$+8X43/8Xd8 thiCUPPEDtimSS+...
0
votes
0answers
44 views

CentOS: / (root) partition reached 90%

We are facing an issue in our production system, running on Cent OS 7. The / (root) partition reached 90% of disk space but we don’t have any huge files / hidden files on that machine. Kindly help us ...
0
votes
0answers
44 views

Kernel panic on Dell R710 Kernel 4.4.1

We are running Debian 7.9 server with kernel 4.4.1 on Dell R710 (Intel(R) Xeon(R) CPU X5670 @ 2.93GHz) and after some time (maybe once a month) server stop working and I see on a screen the kernel ...
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votes
0answers
20 views

Having trouble figureing out how copy_from_user works

I'm currently trying to create a system call in C for a custom linux kernel. I'm using the copy_from_user to copy user level data to a local kernel variable, but I always seem to getting the EFAULT ...
0
votes
0answers
10 views

Is it possible to run CMAN without configfs?

I run a custom 3.18.x kernel that does not have configfs enabled. Is it possible to run CMAN cluster management without configfs? If necessary it would be much easier for me to rebuild CMAN than it ...
0
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0answers
35 views

Log file bloat due to nouveau

Both my kern.log and syslog files have grown to >50Gb and contain a few hundred million lines of: Feb 23 23:32:43 Yawning-Angel kernel: [396111.179453] nouveau E[ PFIFO][0000:05:00.0] PBDMA0: ch 2 [...
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146 views

Got kernel panic with 3w-sas driver after kernel update

I use CentOS 6.7 and I've got kernel panic related to LSI 3ware 9750-4i Controller after kernel update from 2.6.32-431.17.1.el6.x86_64 to 2.6.32-573.12.1.el6.x86_64. It is minor update, so I think it ...
0
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0answers
61 views

EFI shell boot vmlinuz : no filesystem could mount root, tried :

I am trying to boot an installed OS from UEFI shell. This machine doesn't have a legacy boot. Only option is to use EFI shell. I am using a custom compiled kernel-3.18.17. I could load vmlinuz, but ...
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0answers
36 views

X9SRL-F Crashing Ubuntu

We are running a KVM server node on Ubuntu 14.04.3 LTS with some VMs for a while now. About 3 months ago we noticed a random crash at night without any crashdata, the system seemed to be frozen back ...
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0answers
36 views

Kernel config options explained

Can anyone explain what the following options from my centos 5.9 box do CONFIG_HAS_IOPORT=y CONFIG_HAS_DMA=y CONFIG_GENERIC_HARDIRQS=y CONFIG_GENERIC_IRQ_PROBE=y CONFIG_GENERIC_PENDING_IRQ=y ...
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votes
0answers
32 views

Network issues or tcp stack load

I am running a NoSQL (aerospike) cluster on a set of identical hosts (ec2). Once in a while one of them would start timing out on queries and connections, and pings to it would go from < 1ms to 20-...
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0answers
452 views

centos 7: sysctl -p /etc/sysctl.d/50-default.conf returns error

I have rented container from OVH a while ago but last night all of a sudden my machine stopped responding on IP level... after reboot I have noticed the following systemd-sysctl.service - Apply ...
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53 views

OOM Killer when tcpdump is run in system with low memory

I am working on an embedded system with limited memory. Here is the dump from my vmstat: procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu----- r b swpd free buff ...