Monitor a remote computer securely using SNMP (OpenBSD)

The Simple Network Management Protocol (SNMP) lets you query a computer for system monitoring info, like uptime and hard drive capacity

OpenBSD has an SNMP server built in (snmpd), as well as an SNMP client (snmpctl)

OpenBSD includes SNMP info ("mibs") for CARP, relayd, and pf as well as the standard ones

The OpenBSD client is limited to version 2 of SNMP, so we'll use net-snmp, which supports version 3 and therefore authentication and encryption. There's a package for that.

Server (10.0.2.35)

# cat /etc/snmpd.conf

listen on 10.0.2.35
seclevel enc
user "snmp" authkey "s3cr3t00" enckey "s3cr3t00" enc aes auth hmac-sha1

# chown root:_snmpd /etc/snmpd.conf `# root is owner, _snmpd is group`
# chmod u=w,g=r,o= /etc/snmpd.conf `# root write, _snmpd read, other nothing`
# rcctl enable snmpd
# rcctl start snmpd

Need to check your config?

# snmpd -n

Need to debug snmpd?

# snmpd -dvv

Client

# pkg_add net-snmp
# cat /etc/snmp/snmp.conf

defSecurityName snmp
defSecurityLevel authPriv
defPassphrase "s3cr3t00"
defAuthType SHA
defPrivType AES

# chown root:wheel `# root is owner, wheel is group`
# chmod u=w,g=r,o= /etc/snmp/snmp.conf `# root write, wheel read, other nothing`
# snmpwalk 10.0.2.35 | less `# shows much info from remote system`