Linux - The DNS resolver (/etc/resolv.conf)

The file /etc/resolv.conf is used by the resolver a library that determines the IP address from an host name. It defines the DNS.

Two Domain Name System (DNS) resolver parameters (timeout and attempts) are set by default to low values when the operating system is installed.

Typical resolve.conf file:

[[email protected] ~]# cat /etc/resolv.conf
; generated by /sbin/dhclient-script
search cornac.net
nameserver 192.168.2.1

where:

• search cornac.net: The search list is normally determined from the local domain name; by default, it contains only the local domain name.
• nameserver Name-server-IP-address: Point out to the DNS server. Up to 3 name servers may be listed.

3 - In the case of an Oracle database installation

3.1 - Options

These low values may cause attempted network connections to an Oracle database to fail. If this happens, add or update the following entries to these minimum settings in the /etc/resolv.conf file on each server node:

options attemps:5
options timeout:15

3.2 - nameserver

The nameserver is used by the listener. If the value is set with a bad DNS server, it may cause very slow connection. Suppress the parameter or set a good value.