Ubuntu – How to start named in IPv4 mode using systemd

bindnamed-confsystemdUbuntu

How can I configure my Ubuntu 15.04 bind9 to stop resolving queries with IPv6?

TL;DR

I'm using bind9 on my Ubuntu 15.04 machine. It seems like my named server is trying to resolve alot of queries using IPv6.

29-Jul-2015 01:03:28.926 lame-servers: error (network unreachable) resolving 'vassg.omniroot.com.edgesuite.net/A/IN': 2600:1401:2::2#53
29-Jul-2015 01:03:30.073 lame-servers: error (network unreachable) resolving 'askubuntu.com/A/IN': 2001:503:231d::2:30#53
29-Jul-2015 01:03:30.516 lame-servers: error (network unreachable) resolving 'stackapps.com/A/IN': 2001:503:a83e::2:30#53
29-Jul-2015 01:03:30.533 lame-servers: error (network unreachable) resolving 'stackapps.com/AAAA/IN': 2400:cb00:2049:1::adf5:3b69#53

When googling I ended up with the solution to start the named service in IPv4 mode only by adding a -4 switch. I tried modifying my /etc/default/bind9 into this:

/etc/default/bind9

# run resolvconf?
RESOLVCONF=yes

# startup options for the server
OPTIONS="-4 -u bind"

But I still ended up having alot of failed resolvs using IPv6.

So I checked the switches used to start named with systemd

mippy@heimdal:~/src/servermon$ sudo service bind9 status
● bind9.service - BIND Domain Name Server
   Loaded: loaded (/lib/systemd/system/bind9.service; enabled; vendor preset: enabled)
  Drop-In: /run/systemd/generator/bind9.service.d
           └─50-insserv.conf-$named.conf
   Active: active (running) since ons 2015-07-29 01:11:44 CEST; 25min ago
     Docs: man:named(8)
  Process: 6879 ExecStop=/usr/sbin/rndc stop (code=exited, status=0/SUCCESS)
 Main PID: 6884 (named)
   CGroup: /system.slice/bind9.service
           └─6884 /usr/sbin/named -f -u bind

So it seems like named is started with /usr/sbin/named -f -u bind. Not what I expected from my /etc/default/bind9.

How can I configure named with -4 switch?

Best Answer

This is the procedure to update named options after Ubuntus switch to systemd:

cp /lib/systemd/system/bind9.service /etc/systemd/system/bind9.service

edit

/etc/systemd/system/bind9.service

change

ExecStart=/usr/sbin/named -f -u bind

into

ExecStart=/usr/sbin/named -4 -f -u bind

then

systemctl daemon-reload
service bind9 restart

double check that the change has taken effect:

mippy@heimdal:~/src/servermon$ sudo service bind9 status
● bind9.service - BIND Domain Name Server
   Loaded: loaded (/etc/systemd/system/bind9.service; enabled; vendor preset: enabled)
  Drop-In: /run/systemd/generator/bind9.service.d
           └─50-insserv.conf-$named.conf
   Active: active (running) since ons 2015-07-29 11:09:26 CEST; 5min ago
     Docs: man:named(8)
  Process: 20737 ExecStop=/usr/sbin/rndc stop (code=exited, status=0/SUCCESS)
 Main PID: 20742 (named)
   CGroup: /system.slice/bind9.service
           └─20742 /usr/sbin/named -4 -f -u bind

For more information, check out this suse doc page. It should be applicable for us Ubuntu users as well. https://www.suse.com/documentation/sled-12/book_sle_admin/data/sec_boot_systemd_custom.html

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