Where is right place for sysctl redefined values?

I have:

> uname -a
Linux note 3.1.0-1-amd64 #1 SMP Tue Jan 10 05:01:58 UTC 2012 x86_64 GNU/Linux

> cat /etc/debian_version 

> tail -n 2 /etc/sysctl.conf   

But after each reboot net.ipv6.bindv6only still 1

4 Answers 4


Check if there is a file in /etc/sysctl.d with your parameter. These files override the /etc/sysctl.conf file...

  • yep. i found /etc/sysctl.d/bindv6only.conf thanks Feb 1, 2012 at 11:18
  • /etc/sysctl.d/README states the precedence order and specifically "use /etc/sysctl.conf directly, which overrides anything in this directory." Is the README wrong?
    – lkanab
    Jan 3, 2017 at 7:59
  • If you have a recent Debian, it load the /etc/sysctl.conf at the last one (see 99-sysctl.conf file). This topic is for old Debian (before 2014). In the new versions, the files must have a number to know the order to use.
    – Dom
    Jan 3, 2017 at 8:35
  • @Dom i am using ubuntu 16.04 LTS . Still it not taking /etc/sysctl.conf neighter 99-sysctl.conf as precedence file. anything still missing?
    – jit
    Dec 27, 2017 at 13:26
  • Check the syntax of the files. They should be used. In 16.04, the files must have a XX- and .conf at the end. Try to restart procps service and look at logs, it can be an error
    – Dom
    Dec 27, 2017 at 22:27


/etc/init.d/procps.sh comes too early in the boot process to apply a lot of sysctl's. As it runs before networking modules are loaded and filesystems are mounted, there are quite a lot of commonly-used sysctl's which are simply ignored on boot and produce errors to the console.

All documentation on the net referring to changing certain settings in /etc/sysctl.conf such as net.ipv4.netfilter.ip_conntrack_max is wrong for Ubuntu & Debian.

Finally, "It seems to me it is a Debian Squeeze bug, see here for an example and workaround: http://wiki.debian.org/BridgeNetworkConnections

In the latter case, the procps init script should take care of loading them during boot. However, on Squeeze it does not, and you need to restart it from /etc/rc.local (or similar):

# /etc/rc.local

# Load kernel variables from /etc/sysctl.d
/etc/init.d/procps restart

exit 0

If you use ufw (uncomplicated firewall) you really need to change the values in /etc/ufw/sysctl.conf as the configuration here overrides /etc/sysctl.conf one.

  • Thank you. But no, i did not use ufw. Problem was solved, data was redefined in /etc/sysctl.d Aug 17, 2012 at 3:34
  • 1
    Damn I was pulling my hair on this for hours. I thought it was issue 50093, but this was it. Thank you, thank you, thank you!
    – Sentient
    Oct 9, 2019 at 23:24
  • 8 years later this is still relevant. Confirmed to be the case on Ubuntu server 20.04 running UFW Nov 8, 2020 at 4:24

This is set by the procps init script. make sure this init script is enabled with update-rc.d procps enable. If it is enabled you should expect a link from a file in /etc/rcS.d to /etc/init.d/procps. If this init script is working correctly manually running /etc/init.d/procps restart should make the setting.

  • You mean Debian doesn't read sysctl.conf by default? wow. Jan 31, 2012 at 18:59
  • it reads sysctl by default. the /etc/init.d/procps mecahnism is the default mechanism. If my answer works, it is because this init script was disabled for some reason, which might be a bug. A bug causing this would not be surprising since he is running either the testing or unstable release of debian (or some combination thereof)
    – stew
    Jan 31, 2012 at 19:06
  • > sysctl net.ipv6.bindv6only net.ipv6.bindv6only = 1 doesnt works Feb 1, 2012 at 11:17

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