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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8 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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21 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 ...
2
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0answers
24 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
20 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
52 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
18 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
24 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
votes
0answers
41 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
52 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
votes
1answer
485 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
23 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
39 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
23 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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vote
1answer
27 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
108 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
27 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
1answer
90 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 ...
1
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0answers
53 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
25 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 ...
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0answers
136 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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votes
0answers
279 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
votes
3answers
167 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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votes
1answer
132 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 ...
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1answer
64 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 ...
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1answer
86 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 ...
2
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0answers
1k 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
142 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
37 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 ...
0
votes
0answers
277 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
36 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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1answer
255 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
votes
1answer
48 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
votes
0answers
265 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
vote
1answer
137 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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votes
1answer
52 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 ...
2
votes
1answer
287 views

CentOS, kernel: out of memory

Hope you can help me with the following problem. We are running a CrushFTP service on a CentOS release 6.6 (Final) system. But nearly every week the service crashes. So I take a look at the logs and ...
1
vote
0answers
54 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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votes
0answers
44 views

How to hot add a new disk with virsh attach-disk?

I'm trying to add a new LVM disk to my guest machine (Ubuntu 14.04.1) by doing the following on the host: lvcreate -L 14G -n vm_vm005_data3 vg00 virsh attach-disk vm005 /dev/vg00/vm_vm005_data3 ...
0
votes
1answer
288 views

snmpd does not update date due to filesystem access error in new ubuntu versions

My Cacti stopped graphing network data for servers that I monitor using snmp. I am able to manually query the corresponding counter using snmpget $ snmpget -v 2c -c XXX XXX .1.3.6.1.2.1.31.1.1.1.6.4 ...
1
vote
1answer
39 views

How to disable ip_forward for Ubuntu server

This is the state of my server right after booting: root@vzu01-ubuntu:~# cat /proc/sys/net/ipv4/ip_forward 1 There is no other enabled ip_forward configuration: root@vzu01-ubuntu:~# grep -r ...
1
vote
2answers
501 views

Wchan section in ps output not showing anything

I know that if a process go into D state then it means that it is in uninterruptable state. The process can not be killed by any signal. It will only come out of that state on reboot or if I/O wait is ...
0
votes
1answer
245 views

Diskless node. Unable to mount root fs via NFS

Server: CentOS 7 NFS root filesystem for client and Kernel: Slackware 14.1 I enabled "Root file system on NFS" and "IP: kernel level autoconfiguration" with "DHCP,BOOTP,RARP" support, recompiled the ...
0
votes
1answer
231 views

Building CentOS 6 kernel with KVM support fails due to MMU

When building the latest Linux kernel for CentOS it turns up the following error CC [M] arch/x86/kernel/iosf_mbi.o CC arch/x86/kvm/../../../virt/kvm/kvm_main.o CC ...
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0answers
267 views

Add nmi=ignore to default xen boot option

I updated my Xenserver from 6.2 to 6.5 and the server won't boot unless I deactivate Hyper Threading via BIOS (INtel Server Board). I can fix that using a special kernel parameter (nmi=ignore) but I ...
0
votes
1answer
756 views

Debian 8 Jessie with older Kernel - Do I have to expect problems?

I have a virtual server that I tried to upgrade from Debian 7 to Debian 8. Unfortunately, I cannot use the new kernel: it still uses version 3.2.41-042stab108.2. Everything else seems to have been ...
0
votes
1answer
387 views

How can I modify kernel command line in CoreOS

I am trying to set 'net.ifnames=0' on the kernel command line for CoreOS. In older loads (including the current stable 647.0.0), you could mount /dev/sda1 and edit the grub.cfg file under ...
0
votes
1answer
182 views

Debian/Installer Preseed Remove Post Install Kernel Options + Multi NIC Preseed Tip

In light of recent automation trends, I would like to be able to fully automate an install of Ubuntu. My my first problem was auto selection of the bootif with multiple NICs break Ubuntu/Debians ...
0
votes
2answers
27 views

Posix map fs path to syspath

Is there a safe way to map a filesystem path to a /sys/block/ node. For instance on my system (Ubuntu) my / path is mounted from /dev/disk/by-uuid/7f6a93a7-1e63-48a3-a7e3-b336a2f9dbf7 which is a ...
0
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0answers
113 views

Kernel upgrade issue

I am trying to upgrade kernel on OnApp VM. Currently installed kernel is 2.6.32-279.22.1.el6.x86_64. The new version available is 2.6.32-504.16.2.el6.x86_64. I installed new kernel ...