OpenWRT uses UCI (/etc/config/snmpd) to generate the /etc/snmp/snmpd.conf , so you cannot simply edit this file and restart snmpd.
翻译：
OpenWRT利用UCI（/etc/config/snmpd）去生成snmp的配置文件/etc/snmp/snmpd.conf，因此你不能简单的编辑此文件，需要重启snmpd进程。
重新启动snmpd进程（./etc/init.d/S50snmpd restart）后，会保存到配置文件/etc/snmp/snmpd.conf中去。