"No NSS support for mDNS detected" in system log(/var/log/messages)

刘泽宇

现象：
There is a warning message  in /var/log/messages:

<date> <hostname> avahi-daemon[####]: WARNING: No NSS support for mDNS detected, consider installing nss-mdns!


修改：
Installed avahi package and run /etc/init.d/avahi-daemon script.

原因：
This is caused by the lack of libnss_mdns library, which is referred by avahi to support mDNS(Multicast DNS) via NSS(Network Security Service). The avahi-daemon tries to open the shared library named "libnss_mdns*.so.2", In this case there is no such library installed onto the system, therefore avahi-daemon complains about no support for mDNS and logs the warning message in the system log.

nss-mdns is a plugin for the GNU Name Service Switch (NSS) functionality of the GNU C Library (glibc) providing host name resolution via Multicast DNS (using Zeroconf, aka Apple Bonjour / Apple Rendezvous ), effectively allowing name resolution by common Unix/Linux programs in the ad-hoc mDNS domain ".local". mDNS is basically used only by Apple PC to find out the server/client name each other automatically. But if the network is configured without Apple PCs, or with static hostnames or static ipadresses(in most cases), mDNS is not necessary.


处理方法：
Since there is no libnss_mdns library provided for Oracle Linux by Oracle, and mDNS is not necessary for most systems, the warning message can safely be ignored.