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't resolve issue: iptables: No chain/target/match by that name

So I am trying to setup shorewall firewall on my linux vps. The vps is running ubuntu 12.10. When I type $ shorewall check I get this error. iptables: No chain/target/match by that name. ERROR: ...
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9answers
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Maximum number of files in one ext3 directory while still getting acceptable performance?

I have an application writing to an ext3 directory which over time has grown to roughly three million files. Needless to say, reading the file listing of this directory is unbearably slow. I don't ...
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How can I tune the initial TCP retransmit timeout?

The initial TCP RTO value of 3s is too long for most LAN-based applications. How can I tune it lower? Is there a sysctl?
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1answer
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Flush processes consume too much of CPU

The Server is EC2 Instance, it stands for saving files to NAS (NFS) from HTTPD. The processes like flush-0:32 consume over %90 of CPU and load average: 65.50, 64.02, 66.59. According the graph, it's ...
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3answers
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kswapd often uses 100% CPU when swap is in use

Most of the time when my computer starts to need swap, I see a massive spike in CPU usage (kswapd0 is consistently using 99%-100% CPU). According to top, the time is spent in sy (system/kernel) not wa ...
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5answers
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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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4answers
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In CentOS 6.x, how can I upgrade to Kernel 3.4?

I have a server running CentOS 6.2 with kernel version 2.6.32, but I need to increase my application Performance. The Kernel Version 3.4 has x32abi which can improve the performance so i want to ...
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How can I see logs in a server after a kernel panic hang?

I am running a production gentoo Linux machine, and recently there was a situation where the server hung in my co-located premises and when I got there I noticed that the server was hung on what ...
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Linux: Why does the CPU frequency fluctuate when using the performance governor?

I'm using a Debian 8 amd64 machine for benchmarking. During experimentation, I would like the CPU to operate at a fixed frequency (preferably the maximum possible). This will rule out the CPU clock ...
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1answer
180 views

kswap using 100% of CPU even with 100GB+ of RAM available

I'm running a Centos 7 ESXi VM with almost 300GB of RAM and 24 vCPUs. The average load is 3 and apps almost never use more than 150GB of RAM. The rest of the available memory is used by Linux for ...
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1answer
542 views

Installed 2TB disk in ubuntu server, dmesg reports it as 9444732965540666 MB

I've have an ageing Linux server running on Dell PowerEdge hardware, with a SAS 5IR RAID controller. It has a pair of SAS 146Gb disks in a RAID 1 configuration that has the OS and other software. I ...
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1answer
145 views

Ubuntu 14.04 TCP established hash table entries

A bit of background I am running two servers under high traffic one with ubuntu 12.04 (linux 3.2.0-69-generic) and one with ubuntu 14.04 (linux 3.13.0-52-generic). I am now trying to secure both. ...
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2answers
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Log - Server kernel: INFO: task httpd:000000 blocked for more than 120 seconds

Almost everyday my server is crashing due to hight server load, and even restarting apache or mysql can't solve the problem. I need to reboot the server to solve, or it crash again due to the high ...
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1answer
2k views

Debian squeeze kernel backports upgrade - moving forward?

It was suggested to update my Debian Squeeze kernel to something more recent. We chose 2.6.38 and used Debian Backports to install linux-image-2.6.38-bpo.2-amd64 following these instructions ...
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5answers
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Very low performance of raid6

I noticed that writing to raid-6 is very low, but when I make tests with hdparm the speed is reasonable: dd if=/dev/zero of=/store/01/test.tmp bs=1M count=10000 Gives: 50Mb/s or even less. The ...