SNMP logging a lot to Syslog

SNMPd is a systemd, unit now.

So the file we have to modify is not /etc/default/snmpd but /etc/systemd/system/multi-user.target.wants/snmpd.service

We just need to change -Lsd to -LS4d to only log warning level messages and get rid of the millions of UDP connections.

[Unit]
Description=Simple Network Management Protocol (SNMP) Daemon.
After=network.target
ConditionPathExists=/etc/snmp/snmpd.conf

[Service]
Environment="MIBSDIR=/usr/share/snmp/mibs:/usr/share/snmp/mibs/iana:/usr/share/snmp/mibs/ietf:/usr/share/mibs/site:/usr/share/snmp/mibs:/usr/share/mibs/iana:/usr/share/mibs/ietf:/usr/share/mibs/netsnmp"
Environment="MIBS="
Type=simple
ExecStartPre=/bin/mkdir -p /var/run/agentx
ExecStart=/usr/sbin/snmpd -LS4d -Lf /dev/null -u Debian-snmp -g Debian-snmp -I -smux,mteTrigger,mteTriggerConf -f
ExecReload=/bin/kill -HUP $MAINPID

[Install]
WantedBy=multi-user.target

After that run:

systemctl daemon-reload
systemctl reload snmpd