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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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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0answers
15 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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2answers
69 views

how to tell if NIC has multiqueue enabled?

Can anyone tell me what command i run to determine if my 10G NIC is running in single RX-TX queue mode or multiqueue? It looks like it only has 1 RX/TX queue according to cat /proc/interrupts ...
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0answers
10 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 ...
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1answer
47 views

nvme device dropouts - I/O 0 QID 0 timeout, controller disabled

We have 6 Supermicro servers all of the same (or very similar spec), Over the last two weeks one of them has been dropped an NVMe disk at random times due to: [ 66.856719] nvme 0000:03:00.0: I/O 0 ...
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16 views

Kernel errors with 3.13.0-71-generic

After upgrading several hosts to Ubuntu 12.04.5 LTS with the LTS enablement stack (linux-generic-lts-trusty 3.13.0.40.35), we are seeing a sudden spike in kernel errors. These only begin to occur ...
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0answers
35 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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1answer
52 views

How to know if the reboot cause is a linux kernel crash? [closed]

When my system reboot. I want to know the cause of the reboot especially when the reboot cause is a kernel crash. Are there a way to know if the reboot cause is linux kernel crash? like read ...
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0answers
9 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 ...
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0answers
23 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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3answers
241 views

How to fine tune TCP performance on Linux with a 10Gb fiber connection

We have 2 Red Hat servers that are dedicated for customer speedtest. They both use 10Gb fiber connections and sit on 10Gb links. All network gear in between these servers fully support 10Gb/s. Using ...
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2answers
31 views

Why takes CLEARING swap soo long?

Why is moving from RAM to swap fast and from swap to RAM very slow? When I run program that needs more memory that is available, I see that the RAM is prety quickly "cleaned" by moving unsused (=the ...
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1answer
156 views

High load average, but low CPU/IO figures - how to diagnose? (dmesg output included)

We have a Hadoop cluster where arbitrary data nodes will lock up. This is usually pre-ceded by ever-increasing load averages, with CPU and IOwait remaining practically non-existant. The use case for ...
3
votes
1answer
242 views

systemd Using 4GB RAM After 18 Days of Uptime

I have a web server running CentOS 7, on which the systemd process is using nearly 4 GB of RAM after a couple weeks of uptime. RAM usage is increasing steadily at about 200MB per day. This and related ...
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1answer
20 views

What happens when I press Ctrl+C when e2fsck running?

What happens when I press Ctrl+C when e2fsck running ? will it go to command prompt ? or it will reboot & then the server again goes to fsck ? Reason Why I want ? I want the server to up ...
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0answers
104 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 ...
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0answers
30 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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0answers
44 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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2answers
70 views

Mysql locks up linux server during high load

Every day during the generation of some reports the mysql process takes up 1 or 2 cores (100%). The problem is that the whole server becomes unresponsive during that time. I can't ssh, postfix doesn't ...
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0answers
25 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
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 ...
4
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0answers
45 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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1answer
81 views

How to edit /proc/partitions file in linux

I know /proc is a VFS and cannot be updated by user from shell prompt. this is my understanding from the beginning. Now , I am writing one code and where I am taking care of corrupted /proc/partitions ...
4
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1answer
1k views

Why are connections in FIN_WAIT2 state not closed by the Linux kernel?

I have an issue in a long-lived process called kube-proxy being part of Kubernetes. The problem is that from time to time a connection is left in FIN_WAIT2 state. $ sudo netstat -tpn | grep ...
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2answers
29 views

How to unlist partitions from fdisk command in linux

While working on one of my server I noticed that there are no partitions listed under "fdisk -l" command. However the machine is working just fine. Wanted to know following things if anyone can help. ...
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1answer
47 views

How to get notified when a server started with gcloud is completely up

Is there a way to detect when a server is completely up (i.e. finished all the kernel startup tasks)? This is a Google Compute Engine Instance. Nov 18 10:58:51 image-name google: No startup script ...
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0answers
27 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 ...
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1answer
34 views

Postgresql calculate kernel share memory?

We are running PGSQL 9.2 and following are hardware specs OS: CentOS7 64bit CPU: 24 Memory: 32GB Disk: SSD I want to calculate shmmax/shmall values then what would be the good way? I google it and ...
2
votes
1answer
156 views

NVMe speed degradation after kernel upgrade

We are testing the speed of two Intel DC P3600 NVMe drives on a CentOS 7.1 system. They are configured in a software RAID1 using mdadm. After upgrading the kernel from the (very old) 3.10 to the ...
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0answers
30 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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1answer
153 views

PXE boot kernel panic

I am having trouble setting up a PXE boot server. I've got isc-dhcp-server running, tftp-hpa serves the files over tftp (verified works), and apache2 hosts the rootfs image. The PXE client seems to ...
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0answers
59 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 ...
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0answers
31 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 ...
1
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0answers
181 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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0answers
411 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 ...
4
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3answers
182 views

How to prevent Alice to kill a process, but allow Bob to uninstall it?

I know Bob who is a system admin. Bob needs to deploy software Foo to Alice's work device based on Windows NT (XP onwards). Foo is security software. It is not malicious. Alice has local admin ...
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1answer
181 views

Linux Server: Too Many Open Files

I have an application running on Linux Server. But server suddenly stopped responding but when I ping from other machine to server it allowed to ping but was not allowing to login into the server. Not ...
0
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1answer
65 views

IBM - Kernel problems [closed]

I bought an IBM x3850 and wanted to install Ubuntu on it. Then it said, that it can not find hard drives... After some time i figured out that I need to type in the kernel parameter iommu=soft. The ...
0
votes
1answer
118 views

Simpler way to add eth0 support in initrd.img (Centos)

I am trying to deploy clone image via pxeboot on hard disk. For this I want to use dd tool. I am aware that there are few tools like fog and clonezilla which does similar thing but this is university ...
5
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0answers
2k views

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 ...
2
votes
1answer
150 views

Linux ext3 Directory index full - internals

Encountered a situation today on a server that has me wondering. Here's the scenario: Syslog shows: kernel: EXT3-fs warning (device sdb2): ext3_dx_add_entry: Directory index full! Found the ...
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0answers
49 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 ...
5
votes
2answers
3k views

CentOS 6.6 (Final) - yum kernel upgrade troubles

Well-being everybody, I'm a SysAdmin Junior managing 3 CentOS Virtual (Web)Servers, this morning I'm facing some troubles with package manager yum. As usual operation, this morning I've run the ...
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0answers
342 views

Debian Jessie 8 idle on fresh install always a little too high, shows rcu_sched ksoftirqd kworker causing cpu load

Are the days of 0.0 cpu load on an "idle" server gone? I have another server (centos/redhat) 32GB ram that actually runs apache/MySQL/Lamp, mono, redmine/ruby, and other junk and its still shows me ...
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0answers
42 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 ...
1
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1answer
407 views

cpufrequency scaling with debian 8.1 and Intel XEON E5-1650 v3

I want my server with debian 8.1 not to use cpu scaling but always run at the highest possible frequency. I have installed cpufrequtils $ dpkg -l | grep cpufreq ii cpufrequtils ...
0
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1answer
51 views

Rebooting a production CentOS 6 server that's been up for 365 days

I noticed today when running uptime that my server has been up for exactly 365 days. Which led me to google "should I periodically reboot my server". Which led me to the knowledge that YES, I should ...
0
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0answers
289 views

task nginx:4164 blocked for more than 120 seconds

My server was working fine for 173 days then it started to happen. Upgrading CentOS 6.6 kernel to latest one didn't helped. Rebooting helps for about 10 minutes then it starts all over again. I'm ...
1
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1answer
184 views

centos doesn't reply to icmp request

I have the following situation: Centos7, 2 NIC with following setup: em2(NIC2) : 82.79.24.74/29 82.79.24.75/29 em3(NIC3) : 192.168.0.240/24 192.168.133.240/24 ...
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1answer
67 views

AWS Instance Kernal-id

I am running a Windows Server instance in AWS Cloud.I have created a snapshot for the same. When i'm trying to create a AMI from my snapshot it is asking Kernel-ID and RAM Disk ID. I don't know what ...