In this blog, We will discuss how to setup DNS server on Linux for Oracle 11g R2 RAC setup.
With Oracle 11gR2 where we need to provide SCAN IP we need
to configure either DNS or GNS. Giving SCAN
ips on host file does not work.
Instead of any other domain, I will be using LOCALDOMAIN.
Following is our environment to demonstrate DNS server
setup.
Linux
rac1.localdomain 2.6.39-300.26.1.el5uek #1 SMP Thu Jan 3 18:33:10 PST 2013 i686
i686 i386 GNU/Linux
Install following packages on
bind-9.3.6-20.P1.el5_8.5.i386.rpm
bind97-utils-9.7.0-17.P2.el5.i386.rpm
bind-utils-9.3.6-20.P1.el5_8.5.i386.rpm
bind97-chroot-9.7.0-17.P2.el5.i386.rpm
These RPM’s install and create files related to
bind/DNS server that we use.
Go to /etc directory and run following command.
[root@rac1 etc]# ls -tlr named*
lrwxrwxrwx
1 root named 41 Jun 22 10:56 named.rfc1912.zones ->
/var/named/chroot/etc/named.rfc1912.zones
lrwxrwxrwx
1 root named 51 Jun 22 10:56 named.caching-nameserver.conf ->
/var/named/chroot/etc/named.caching-nameserver.conf
and now copy “Named.Caching-nameserver.conf” file
into as /etc/named.conf
[root@rac1 etc]# cp
/var/named/chroot/etc/named.caching-nameserver.conf named.conf
ls -ltr named*
lrwxrwxrwx
1 root named 41 Jun 22 10:56
named.rfc1912.zones -> /var/named/chroot/etc/named.rfc1912.zones
lrwxrwxrwx
1 root named 51 Jun 22 10:56
named.caching-nameserver.conf ->
/var/named/chroot/etc/named.caching-nameserver.conf
-rw-r-----
1 root root 1230 Jun 22 11:09 named.conf
Now! Edit the named.conf file. The final
named.conf file should look like following.
options {
listen-on port 53 { 127.0.0.1; ***.***.**.***; }; ßIP
of your DNS server
listen-on-v6 port 53 { ::1; };
directory "/var/named";
dump-file
"/var/named/data/cache_dump.db";
statistics-file "/var/named/data/named_stats.txt";
memstatistics-file "/var/named/data/named_mem_stats.txt";
//
Those options should be used carefully because they disable port
//
randomization
//
query-source port 53;
//
query-source-v6 port 53;
allow-query { localhost; };
allow-query-cache { localhost; };
};
logging {
channel default_debug {
file "data/named.run";
severity dynamic;
};
};
view localhost_resolver {
match-clients { localhost; };
match-destinations { localhost; };
recursion yes;
include "/etc/named.rfc1912.zones";
};
/*NOTE I
have added following two sections in named.conf file. One for localdomain and one for reverse lookup . You can provide
something like 0.168.192 or any other that matched your network*/
zone "localdomain" IN {
type master;
file "localdomain.zone";
allow-update { none; };
};
zone "***.***.***.in-addr.arpa." IN {
type master;
file "0.168.192.in-addr.arpa.";
allow-update { name; };
};
Now! Edit /var/named/localdomain.zone or if you
are creating it for your own domain zone than better is to copy and rename
localdomain.zone file. Eg zbc.com and make appropriate changes.
Final file should look like following:
[root@rac1 etc]# cat /var/named/localdomain.zone
$TTL
86400
@
IN SOA localdomain root (
42 ; serial (d. adams)
3H ; refresh
15M ; retry
1W ; expiry
1D
) ; minimum
IN NS localdomain
localdomain
IN A 127.0.0.1
rac1-vip IN A **.**.**.221
rac2-vip IN A **.**.**.222
rac-scan IN A **.**.**.11
rac-scan IN A **.**.**.12
rac-scan IN A **.**.**.13
Now create a file for reverse lookup. Change the
name of your file as per your requirement. In our case we will be creating
0.**.**.in-addr.arpa.
The content of file should look like following:
$ORIGIN 0.168.192.in-addr.arpa.
$TTL 1H
@ IN SOA localdomain. root.localdomain. ( 2
3H
1H
1W
1H )
0.168.192.in-addr.arpa. IN NS localdomain.
221 IN PTR rac1-vip.localdomain.
222 IN PTR rac2-vip.localdomain.
11 IN PTR rac-scan.localdomain.
12 IN PTR rac-scan.localdomain.
13 IN PTR rac-scan.localdomain.
Now! Stop and restart named service as follows
[root@rac1 etc]# service named stop
Stopping named:
[ OK ]
[root@rac1 etc]# service named start
Starting named: [
OK ]
[root@rac1 etc]# chkconfig named on
Now! Modify
/etc/resolv.conf file and final file should look like following:
[root@rac1 etc]# cat /etc/resolv.conf
# generated by /sbin/dhclient-script
nameserver 127.0.0.1
search localdomain
Further! Change /etc/nsswitch.conf and following
in file.
hosts: dns files nis
restart NSCD service
using following command.
/sbin/service nscd
restart
Now run following
command to check if DNS working or not. As you can see its working.
[root@rac1 etc]#
nslookup rac-scan.localdomain
Server: 127.0.0.1
Address: 127.0.0.1#53
Name: rac-scan.localdomain
Address: 192.168.0.13
Name: rac-scan.localdomain
Address: 192.168.0.11
Name: rac-scan.localdomain
Address: 192.168.0.12
[root@rac1 etc]#
nslookup rac1-vip.localdomain
Server: 127.0.0.1
Address: 127.0.0.1#53
Name: rac1-vip.localdomain
Address: 192.168.0.221
[root@rac1 etc]#
nslookup rac2-vip.localdomain
Server: 127.0.0.1
Address: 127.0.0.1#53
Name: rac2-vip.localdomain
Address: 192.168.0.222
