16.10 systemd-resolved - want to disable IPv6?

**KillerKelvUK** · February 7th, 2017

Just want to stop a process listening for a connection that will never come is all. Here (http://manpages.ubuntu.com/manpages/...network.5.html) says to ensure that IPv6 is disabled on the interface which it is but still I see the process is listening on a tcp6 port...

Code:

netstat -tulpn gives...

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
...         
tcp6       0      0 :::5355                 :::*                    LISTEN      1166/systemd-resolv 
...     
udp6       0      0 :::5355                 :::*                                1166/systemd-resolv

/etc/sysctrl.conf as the following lines included...

Code:

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1
net.ipv6.conf.wlp2s0.disable_ipv6 = 1

Any recommendations/ideas welcome?

**geeksmith** · February 7th, 2017

Did you reboot or run a sysctl command after editing /etc/sysctl.conf? Did you edit /etc/sysctl.conf or /etc/sysctrl.conf (seems like you may have mistyped the name in your post, but maybe you didn't)?

After modifying /etc/sysctl.conf, you run this to apply the changes:

Code:

sudo sysctl -p /etc/sysctl.conf

**KillerKelvUK** · February 8th, 2017

Hey sorry, yes its a typo I meant /etc/sysctl.conf. Also ran the commend and manually verified the conf had taken...

Code:

kelvin@blackbookpro:~$ cat /proc/sys/net/ipv6/conf/all/disable_ipv6 
1
kelvin@blackbookpro:~$ cat /proc/sys/net/ipv6/conf/default/disable_ipv6 
1
kelvin@blackbookpro:~$ cat /proc/sys/net/ipv6/conf/lo/disable_ipv6 
1
kelvin@blackbookpro:~$ cat /proc/sys/net/ipv6/conf/wlp2s0/disable_ipv6 
1

but systemd-resolved still shows its poky lil IPv6 head :-/

**geeksmith** · February 8th, 2017

Have you also restarted systemd-resolved? I imagine a reboot at this point may allow all open IPv6 sockets to be released, then prevented at the next boot.

**bearlake** · February 8th, 2017

You can disable it from the Grub as well on boot.

Code:

sudo nano /etc/default/grub

Look for

GRUB_CMDLINE_LINUX="xxxxx" and add the following line to the end <ipv6.disable=1> so it looks like below.

Code:

GRUB_CMDLINE_LINUX="xxxxx ipv6.disable=1"

Code:

sudo update-grub

**KillerKelvUK** · February 8th, 2017

@geeksmith, yup have manually restarted the process with systemctl and also rebooted.

@bearlake, haven't tried it as a boot time parameter so will give that a try and see if it produces different results.

Thanks both.

**KillerKelvUK** · February 10th, 2017

So adding ipv6.disable=1 to the grub cmdline resolved this, albeit it was on-top of the /etc/sysctl.conf conf so will try removing that and re-test but thanks for the help

EDIT:

So no config needed in /etc/sysctl.conf if disabling IPv6 as a kernel boot time parameter.

**bearlake** · February 10th, 2017

Originally Posted by KillerKelvUK

So adding ipv6.disable=1 to the grub cmdline resolved this, albeit it was on-top of the /etc/sysctl.conf conf so will try removing that and re-test but thanks for the help

EDIT:

So no config needed in /etc/sysctl.conf if disabling IPv6 as a kernel boot time parameter.

Glad I was able to help, ran into the same problem 6 months a go.