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Questions tagged [sysctl]

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.

Linux:
The sysctl command and configuration file use the /proc filesystem's sys directory to read information and apply changes.

The Linux Journal has an article about using sysctl, but most for the most complete information look to this description of /proc/sys's contents.

BSD-derived:
The sysctl command is used to read and configure certain system settings. The Handbook describes its general use in more detail, and the FreeBSD Performance Tuning Community Wiki has some ideas.

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Cannot find default value in sysctl - Ubuntu

Im running Ubuntu 14.0.4 LTS and im trying to change some default values to optimize. I run sysctl -a to see all values. I have /etc/sysctl.conf and /etc/sysctl.d/ which has a few 10-*.conf files in it. I want to change…
Kevin
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running or building docker results in net.ipv4.ip_forward being reset

this is on a rhel6 system (docker 1.7.1 from epel). basically, everytime i do a build or a run, i can see that the net.ipv4.ip_forward sysctl gets reset to 0 - which results in the container loosing all network connectivity. i think this is related…
yee379
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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 /etc/security/limits.conf: * hard core unlimited * soft …
Kabb5
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How do you change tcp_congestion_control on OpenVZ?

I have a network of OpenVZ machines that I am testing various congestion control methods on. I need to know how to change the congestion control. Currently I get nothing but permission denied. Is it even possible to change this on this sort of…
Tyler Scott
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Linux webhost security settings in /etc/sysctl.conf

While searching for more ways to secure Linux servers, I found the following /etc/sysctl.conf configuration. It came as is, without much explanation. Before using it on production environment (using Ubuntu 12.04 LTS), I'd like to know the…
Mehdi
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error: "net.ipv4.netfilter.ip_conntrack_max" is an unknown key

I have a problem on Ubuntu 10.04.3 LTS x64 with sysctl net.ipv4.netfilter.ip_conntrack_max . If I run this command on shell, I get back an error: error: net.ipv4.netfilter.ip_conntrack_max" is an unknown key. It occurred on 2 of our machines after…
Arny80Hexa
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Optimize linux for serving http static content

What would be the system tunables to enhance serving static content? Like increase/decrease swappines, how to max out disk caching and so on...
Calin Don
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Is there a location of the sysctl kernel parameters for osX?

I would like to read up on os X kernel parameters. I can find them listed, but where can I find the meaning of them? For example this parameter net.alf.loglevel: 55 which are not in the man pages , for either BSD or osX. How do people know…
chiggsy
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Set sysfs network option before interface is up

I want to set /sys/class/net/wwan0/qmi/raw_ip, and I don't want to do it by writing a shell script to take wwan0 down set it, then put wwan0 back up as a systemd unit. I'm trying this on Raspbian Stretch, but I doubt the distribution matters much…
Joshua D. Boyd
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Is there an ipv6 equivalent for net.ipv4.conf.all.route_localnet

Is there an ipv6 equivalent for net.ipv4.conf.all.route_localnet ? (According to nftables ip6 route to localhost/ ipv6 nat to loopback, there isn't). If not, how the use case described in Port forward with iptables can be solved for ipv6?
AlonaK
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In IPv6 router gets the Router solicitation message, but not respond with Router advertisement

We setup a IPv6 network with two ubuntu systems and we make one PC as HOST and other as ROUTER(based on the concept of SLAAC). The host sent the "Router solicitation" message, but the router not respond with any "Router advertisement". The…
Adersh Ps
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sysctl -p /etc/sysctl.conf reverts to original settings after 1 minute

I need to tweak the kernel params as the Ubuntu minimal install is created for a machine with 256 MB of ram and our server has 32 GB. The issue I am having is that when I execute the command sysctl -p /etc/sysctl.conf, the server reverts back to…
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How does non-namespace specific sysctl variables work in the context of network namespaces?

Let's assume the systctl variables net.ipv4.tcp_wmem and net.ipv4.tcp_rmem. To my understanding, these variables can not be set per-namespace (but very soon apparently). My understanding is that these variables apply to the init net namespace…
sbrattla
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How can I reliably set net.core.ipv4.conf.rp_filter = 0 on CentOS 7?

I would like to disable reverse-path filtering on a CentOS 7 machine. I have a file in /etc/sysctl.d/ that contains the following in an attempt to disable it for all of my network interfaces: net.ipv4.conf.all.rp_filter =…
Jason R
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Debian sysctl config not persisting on reboot

I am running ubuntu 14.04: Linux WEBLB3 3.13.0-79-generic #123-Ubuntu SMP Fri Feb 19 14:27:58 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux I have modified the /etc/sysctl.conf file to set sysctl settings on reboot, it contains this…
John Foley
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