sysctl is a mechanism for controlling options and limits in the Unix-like operating system kernels. Sysctls can be used to tune performance or change behaviors of many subsystems.

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nginx or kernel queueing traffic

We have a setup that looks like this: nginx->haproxy->app servers We are terminating SSL with nginx and it sits in front of everything. During our peak load times, we are experiencing about a 2x ...
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143 views

TCP packet being retransmitted 7 times when sysctl tcp_retries1 is set to 3 - why?

Ubuntu 12.04 I am trying to better understand how many times TCP will attempt to retransmit a packet when it does not receive confirmation the destination received it. After reading the tcp man page ...
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124 views

Difference between ulimit, launchctl, sysctl?

When managing the limits of the operating system (specifically OSX), what is the difference and overlap between the functionality and history of these three tools: ulimit launchctl, launchd sysctl ...
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How to learn max/min value of a sysctl parameter can be in FreeBSD?

I have a simple question. I want to learn max/min value of a sysctl parameter can be. Where can I find bounds of these parameters? Thanks
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935 views

How to make sysctl network bridge settings persist after a reboot?

I am setting up a notebook for software demo purpose. The machine has 8GB RAM, a Core i7 Intel CPU, a 128GB SSD, and runs Ubuntu 12.04 LTS 64bit. The notebook is used as a KVM host and runs a few KVM ...
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How to enable core files on CentOS 6

I am trying to enable core files on a machine running CentOS 6; however, nothing I have tried has produced core files…here is what I have done: Added the following two lines to ...
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36 views

Keepalived process not listening to advertisement

I have a keeplived setup working on RHEL 5.5 working file. Below is strace of keepalived master, which is reading advertisements off the network and sends its advertisement to the network. ...
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48 views

Suspecting Wrong Configuration of Sysctl (Silent TCP Drops?)

I have a high load long TCP connections server and I had to tweak sysctl to make sure I get no errors, At the moment I get no errors, But I think i might get TCP drops without errors. Here is sysctl ...
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181 views

Too many TCP TIME_WAIT on PHP FCGI PORT

There are way too many TIME_WAIT on 127.0.0.1 This is causing PHP FCGI to work way too slow and hence my error log is full of "recv() failed (110: Connection timed out) while reading response header ...
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sysctl tcp_max_syn_backlog dont work

I change value tcp_max_syn_backlog in sysctl in my ubuntu server 10.04 for growing SYN_RECV queue. But isnt work (I flood this server by hping). But, when i change somaxconn (in documentation its ...