Executing the command “ntpq -pn” returns with the error:
# ntpq -p Name or service not known
In some cases, you may also encounter an error shown below:
# ntpq -pn Servname not supported for ai_socktype
The “Name or service not known” error will be seen if the system cannot resolve “localhost” for the ntpq command. Make sure we have pointer to “127.0.0.1 localhost” in /etc/hosts file.
1. Fix the /etc/hosts file to map 127.0.0.1 to localhost, i.e., there must be a line in /etc/hosts that begins with “127.0.0.1” and contains “localhost”.
Note that it is perfectly fine if this line contains additional host aliases in addition to localhost. Example:
# vi /etc/hosts 127.0.0.1 localhost localhost.localdomain myserver myserver.mydomain
That said, in RHEL6, the name “localhost” maps to both 127.0.0.1 and the IPv6 loopback ::1, so while removing the 127.0.0.1 line in RHEL6 would be a bad idea, it would likely not cause ntpq to fail.
2. Also make sure we have pointer to ntp in /etc/services file.
# vi /etc/services ntp 123/tcp ntp 123/udp # Network Time Protocol