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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Can a Linux Kernel be shared between two operating systems?

Quite simple question. I am working on a project to have multiple operating systems (all linux) on the same machine using btrfs subvolumes so that the user can boot to the environment they are ...
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16 views

Centos 7 cpu frequency below the minimum value

Hyeverybody,I have 2 similar Dell PowerEdge r720 server wih the following configuration: CPU: Intel(R) Xeon(R) CPU E5-2630 v2 @ 2.60GHz RAM: 64GB OS: Centos 7 I have noticed, that the in recent 2 ...
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15 views

Analyse kernel crash file on Ubuntu server 11.10

I am experiencing random crashes on a Ubuntu 11.10 server, and for the time being the system can not be upgraded, even tho this distro is very old. uname -r 3.0.0-12-server I've set it up to get a ...
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20 views

Must kernel-version of Ubuntu linux-cloud-tools match the kernel version of linux vm on hyper-v?

Microsoft's recommendations for installing Ubuntu VM's on Hyper-V (note 5) include installing kernel-specific versions of the linux-tools and linux-cloud-tools packages. However, there are also two ...
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2answers
167 views

linux sever interfaces automation

I am using a CentOS server which has about 6 active interfaces with different IPs, I'd want to automatically bring down all the interfaces when any one of the 6 interfaces is down. Is there a way this ...
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21 views

“error: ‘PATH_MAX’ undeclared” when trying to make menuconfig

I have an OVH cloud VPS with Ubuntu 14.04 64 bit server. I needed linux headers which OVH does not provide by default, so I found some tutorials on how to compile the linux kernel from source using ...
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22 views

PCIe card memory regions ignored on linux kernel 3.13

On my system, with kernel 3.13.0-32-generic (Ubuntu Server 14.04.1 LTS) installed, one of the PCIe boards in the system (06:00.0) is having it's memory regions ignored: Interrupt: pin A routed to IRQ ...
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24 views

What are the pros and cons of large receive offload (LRO) vs generic receive offload (GRO)

I have been debugging a scenario where an ESX vmware host is communicating with a virtual linux machine via a virtual switch using TCP/IP. After a congestion event the vmware host is waiting for an ...
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1answer
34 views

Nginx uses both writev() and sendfile()

I noticed that when serving images Nginx is sending images using both writev() when called from a browser such as Firefox, but uses sendfile() to send the image when wgetting the image. Any idea why ...
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29 views

Apache hanging - FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME

We are running Apache 2.2.15 on a CentOS 6.6 server [2.6.32-504.3.3.el6.x86_64] (with FastCGI PHP, mod_pagespeed, mod_spdy, etc) all the most recent versions. Today we had a case where on one of our ...
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2answers
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Effects of configuring vm.overcommit_memory

My VPS web server running on CentOS 5.4 (Linux kernel 2.6.16.33-xenU) irregularly (like once a month give or take a few weeks) becomes unresponsive due to oom-killer kicking in. Monitoring of the ...
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1answer
68 views

Running multiple ubuntu (or other distro) inside Docker containers on CoreOS, is this efficient?

From what I have read I believe CoreOS to be a bare-bones Linux distribution which essentially facilitates running Docker containers that contain any applications or services that you require. From ...
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16 views

What are the advantages NAPI before the IRQ Coalesce?

As known there are two approach to avoid some overheads of hardware interrupts in highload networks, when there are too many hardware interrupts, that switching to them takes too much time. It is very ...
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1answer
273 views

Scientific Linux: soft lockup on quad opteron system

After an impressive uptime of 550 days without trouble our quad opteron system turned into a corrupted system a few days after I mounted an nfs-share from a FreeNAS-box. Ongoing sessions remained ...
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1answer
23 views

IPSEC stack low speed

I am working on Openswan IPSEC Implementation for Linux-kernel 2.6.35.9 My concern is when i do speed test using IPSEC kernel Images and without running IPSEC service i get speed of 40Mbps and ...
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1answer
39 views

My server boots a kernel I don't recognize

On my dedicated server I'm running Debian 7.5 as an OS. I have installed OpenVZ for amd64 architecture to use the benefits of virtualization but after successfully installing it (following these ...
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1answer
56 views

Warning :mounting fs with errors, running e2fsck is recommended

Linux server will hang and when I restart it will take around 2 hours to come up and resume normal operations. I checked the system log files and found mounting fs with errors, running e2fsck is ...
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1answer
69 views

How to disable ipv6 support in Linux entirely?

We are currently setting up a some local network servers to run in a full ipv4 network. I can be sure, that this network don't have ipv6 support, and never will. Next to that, partially because of ...
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2k views

tc u32 — how to match L2 protocols in recent kernels?

I have a nice shaper, with hashed filtering, built at a linux bridge. In short, br0 connects external and internal physical interfaces, VLAN tagged packets are bridged "transparently" (I mean, no VLAN ...
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1answer
49 views

Windows multicast NLB with Linux clients

I'm (on behalf of a client, anyway) having some troubles with Linux accessing a multicast NLB cluster hosted on Hyper-V (waiting for more information on what version, but I don't think the version is ...
3
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1answer
77 views

Unidentifiable processes under Redhat Linux

Upon issuing a ps ax command on a server I see the following processes that I can't identify. Googling them yields nothing useful. Does anybody know what these are or how I would track them down? The ...
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1answer
137 views

enable fanotify on oracle redhat linux kernel 2.6.39-400

As a newbie in linux environment, I am trying to install clamav daemon, which is clamd, on oracle redhat linux 6 kernel EUK 2.6.39-400. It needs to have fanotify enabled in the kernel. As I see there ...
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2answers
3k views

Server won't boot, kernel panic - not syncing

After a reboot of a CentOS 6.2 server we are getting a kernel panic with the following error: Kernel panic - not syncing: Attempted to kill init! Panic occurred, switching back to text console ...
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67 views

INFO : task events/2:69 blocked for more than 120 seconds

I'm using RHEL 6.3 running on VMWare vsphere and aproximatively every month there is this error message and application running above hang until I restart the server: "echo 0 > ...
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65 views

linux not replying to an arp request

I am running linux 3.14 on a system with 2 interfaces. on the first interface, i can access our local network. on the second interface, arp packets come in but linux doesn't send out reply. is it ...
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51 views

The default value for vm.dirty_background_ratio

Wondering why the default value for "vm.dirty_background_ratio" from Linux Server (CentOS and Ubuntu) is set to 40. Is this just a recommendation for safety? Or is there any particular reason why? ...
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68 views

Utility to list and modify kernel modules loaded during system startup

How do I list all kernel modules loaded while system startup? Is there a user space utility to list and modify the modules loaded during system startup? I am working on RHEL6 Desktop and RHEL6 ...
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1answer
47 views

View full program command line arguments in OOM killer logs

Is it possible to view full program command line arguments in OOM killler logs ? What I see now in /var/log/syslog is Memory cgroup out of memory: Kill process 29187 (beam.smp) score 998 or sacrifice ...
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1answer
1k views

web server “task blocked for more than 120 seconds”

my web server is down every 2 days. it became unresponsive and I can only see the message below on the console. task **** blocked for more than 120 seconds. The only way to bring it up is resetting ...
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1answer
59 views

Apply patch to custom kernel manually [closed]

I compiled a RHEL based kernel with a script. I've come to know that our version of kernel is vulnerable to attack and we need to apply security patches. ...
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2answers
11k views

How do I set the default kernel parameters in CentOS for all existing and future kernels?

I'd like to remove the rhgb and quiet kernel parameters which are used by default when the kernel is booted in CentOS 6, but I want this to apply to all currently installed kernels as well as any ...
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1answer
462 views

Cause of page fragmentation on “large” server with xfs, 20 disks and Ceph

Any insight from someone with a bit of experience in the linux IO system would be helpful. Here is my story: Recently brought up a cluster of six Dell PowerEdge rx720xds to serve files via Ceph. ...
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460 views

Linux (non-transparent) per-process hugepage accounting

I've recently converted some java apps to run with linux manually-configured hugepages, as desribed here. I point out "manually-configured" because they are not transparent hugepages, which gave us ...
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5answers
990 views

MySQL 5.5 degraded performance in linux kernel 3.2 compared to 2.6

Our database servers (mainly based on the Debian stable packages (=currently Wheezy) seem to have about 4 times more load for the same workload in kernel 3.2.0-4-amd64 then in it's previous ...
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1answer
59 views

how to determine who is using the slabs?

Is there any way to figure out who or what is allocating size-256 slabs, like in the slabtop output below? I had to reboot a server yesterday that had 5G out of 8G RAM in size-256 slabs and was ...
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systemrescuecd 4.3.1: parted cannot inform kernel of change

I am trying to use parted (3.2) on systemrescuecd (4.3.1), but keep getting the error message similar to below. Error: Partition(s) 2, 3, 4 on /dev/sdd have been written, but we have been unable to ...
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0answers
84 views

task fstrim blocked for more than 120 seconds

I'm experiencing random crashes on my system. I've narrowed the problem to the fstrim program that's launched weekly by cron. In the console, I've got a set of blocked tasks among whigetch I find ...
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1answer
155 views

WANem doesn't boot after install

I'm using WANem live cd (based on knoppix) to perform network bandwidth tests. In order to keep the current configuration, I've installed it on hard disk (using the gui installation tool provided ...
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1answer
429 views

Kernel panic - not syncing: VFS: Unable to mount root

I uploaded a centos 6.2 VMDK to s3 and then converted it to volume using ec2 import volume. Then i took the snapshot of the volume and deleted it.Now I am trying to create a instance from the snapshot ...
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1answer
980 views

RHEL 6.0 upgrading kernel from 2.6.32-71.el6.x86_64 to 2.6.32-358.2.1.el6.x86_64

[root@localhost ~]# rpm -ivh kernel-2.6.32-358.2.1.el6.x86_64.rpm error: Failed dependencies: bfa-firmware < 3.0.3.1 conflicts with kernel-2.6.32-358.2.1.el6.x86_64 [root@localhost ~]# rpm ...
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139 views

shorewall can'T start: UNTRACKED state requires Raw Table in your kernel and iptables

I'm trying setting up my firewall and installed and configured shorewall. Unfortunately I tried to directly configure iptables first, but this didn't work. When I start shorewall, I get this messages ...
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1answer
506 views

dummy network interface in Linux

When i create a dummy network interface and then bring it up it show up being in UNKNOWN state: root@5b8dd2855a9c:# ip l a boom type dummy root@5b8dd2855a9c:# ip l show boom 58: boom: ...
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0answers
55 views

“Nosy Neighbor” and the CFQ scheduler

I'm trying to understand how does using CFQ affects the "Nosy Neighbor" problem. I'll ask it a bit naively, can a "Nosy Neighbor" even exist when using CFQ? Isn't that CFQ should make sure all ...
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2answers
287 views

order 4 allocation failure disaster

Some environment details first: Hardware: Intel Server Board S2600GZ 2 x Intel Xeon CPU E5-2620 64GB DDR3 RAM Intel RAID Controller RS2BL (LSI SAS2108) with 4TB LVM Volume made of SAS disks ...
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1answer
3k views

CentOS 6.3 task blocked for more than 120 seconds

Recently have been getting Zabbix alerts about our mail system being unavailable, the uptime on the machine is 30+ days. I've been tracing the Zabbix logs and it looks like the communication between ...
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1answer
44 views

CentOS 5.10 TCP Sequence Number

We have done a security check on a server and its come back with Linux Kernel TCP Sequence Number Generation Security Weakness. We are looking to correct this being flagged up on the check We are ...
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2answers
512 views

Linux NFS hangs after about 15 minutes

I'm somewhat new when it comes to administering Linux and NFS, so please bear with me. We are trying to setup a small cluster at work. Currently the system is just 2 DELL high-end workstations, ...
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1answer
2k views

Linux Kernel complaining about TSC when selected clock source is Hyper V

We are running RHEL 6 boxes on HyperV with Windows Server 2012. On a few on our RHEL boxes, I am seeing this error in /var/log/messages kernel: Clocksource tsc unstable (delta = -62519781 ns). ...
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2answers
681 views

Linux: echo 3 > /proc/sys/vm/drop_caches takes hours to complete

I have a Thecus N8900 NAS, which is a Linux based file server, providing files via NFS to six clients. For some reason that Thecus support has yet to explain, it runs a script that checks ...
4
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1answer
762 views

linux initcwnd and initrwnd via /etc/sysctl.conf

Folks, As we know, the 3.x kernels have higher TCP default connection values, such as initcwnd and initrwnd. For 2.x friends, is there a way to set these in /etc/sysctl.conf instead of the ip route ...