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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2k 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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202 views

NGINX not responding during DDoS attacks

I'm going to get straight to the point, NGINX doesn't seem to handle any HTTP requests during a DDoS attack using XML-RPC. The server only uses about 1% of the CPU during an XML-RPC DDoS attack. The ...
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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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Redis and Postgresql on same machine: vm.overcommit_memory=?

In the Redis documentation it clearly states that vm.overcommit_memory should be set to 1 to ensure background saving newer fails: http://redis.io/topics/faq HOWVER In postgresql documentation it ...
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nginx monitoring failed to load status page under load

Nginx monitoring script so-called ztc failing to load nginx test page (mostly under highest load to nginx about 2000 rps, which used as proxy), causing errors like "nginx is down" on zabbix, and, in a ...
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Unusually high dentry cache usage leads to PHP performance degradation

We have lots of servers serving lots of requests with apache and php accessing remote memcacheds. But we are experiencing degradation from php side accessing memcached and obtaining lots of memcached ...
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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 ...
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UFW - Set correct kernel params

As every system administrator does, one of the first things i did right after booting up my web server was install ufw and tune/set kernel parameters in /etc/sysctl.conf. By the way, this is my ...
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systemd difference between start and restart

In /etc/sysctl.d folder we have config files are going to be applied at boot time. I use debian 8 with systemd. And now procps is managed by systemd. Please, help me understand, why service procps ...
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sysctl: cannot stat /proc/sys/kernel/exec-shield: No such file or directory

Enable ExecShield protection - ExecShield is security Linux kernel patch to avoid worms and other problems. After Adding to /etc/sysctl kernel.exec-shield = 1 Getting this error sysctl: cannot ...
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Fast Ethernet UDP optimize receive buffers

I have a Linux computer which must receive streaming data from several devices (up to 30 or so) during long terms. This computer is connected to a Fast Ethernet local area network (100 Mbps) where ...