About
The file /etc/resolv.conf is used by the resolver.
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:
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.
Check the DNS nameserver used
How to check the DNS nameserver used
Resolvectl
resolvectl status
Global
Protocols: LLMNR=resolve -mDNS -DNSOverTLS DNSSEC=no/unsupported
resolv.conf mode: stub
Link 2 (eth0)
Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6
Protocols: +DefaultRoute LLMNR=resolve -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 213.186.33.99
DNS Servers: 213.186.33.99
DNS Domain: openstacklocal
Link 3 (wg0)
Current Scopes: DNS
Protocols: +DefaultRoute LLMNR=resolve -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 1.1.1.1
DNS Servers: 1.1.1.1
DNS Domain: ~.
systemd-resolve
systemd-resolve --status
Global
Protocols: LLMNR=resolve -mDNS -DNSOverTLS DNSSEC=no/unsupported
resolv.conf mode: stub
Link 2 (eth0)
Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6
Protocols: +DefaultRoute LLMNR=resolve -mDNS -DNSOverTLS
DNSSEC=no/unsupported
Current DNS Server: 213.186.33.99
DNS Servers: 213.186.33.99
DNS Domain: openstacklocal
Link 6 (wg0)
Current Scopes: none
Protocols: -DefaultRoute LLMNR=resolve -mDNS -DNSOverTLS
DNSSEC=no/unsupported
In the case of an Oracle database installation
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
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.