The ntpd (Network Time Protocol daemon) is a service that runs in the background on Linux systems to keep the system clock synchronized with a remote time server. In some cases, you may see an error message similar to the following when running ntpd:
ntpd[PID]: sendto(IP_ADDRESS): Bad file descriptor
This error typically indicates that ntpd is unable to establish a network connection to the remote time server. This can happen for a number of reasons, including a misconfigured ntp.conf file, network connectivity issues, or firewall rules that block the required ports.
To fix this error, you can try the following steps:
Check the ntp.conf file to ensure that the correct time server IP addresses or hostnames are specified. This file is typically located in /etc/ntp.conf.
Test network connectivity to the time servers using the ping command. For example, if your time servers are time1.example.com and time2.example.com, you can use the following commands:
ping time1.example.com ping time2.example.com
If the ping command is unable to reach the time servers, there may be a network connectivity issue that needs to be resolved.
Check the firewall rules to ensure that the required ports are open. The ntpd service uses UDP port 123 by default, so you will need to ensure that this port is open on both the local and remote systems.
If all of the above steps fail, you can try restarting the ntpd service using the following command:
service ntpd restart
This will stop and start the ntpd service, which may help to resolve any issues with the network connection.
If you continue to experience problems with ntpd, you may need to seek further assistance from your system administrator or a technical support forum.