in /etc/init.d/snmpd, snmpd.conf gets written to /var/run/snmpd.conf:

RUN_D=/var/run
RUN_C=$RUN_D/snmpd.conf

but snmpd searches for its config file in /etc/snmp:/usr/share/snmp:/usr/lib/snmp:/root/.snmp
Solution: Either set RUN_C correct or add "-c /var/run/snmpd.conf" to /etc/default/snmpd

BARRIER BREAKER (14.07, r42625), snmpd - 5.4.4-1