users

Open sessions on a Linux host, by SNMP

Returns the number of open sessions. One watch is offered, with no default threshold.

How it works

The collector reads hrSystemNumUsers (HOST-RESOURCES-MIB): net-snmp counts the sessions the system records in utmp, on the console as well as remote ones (SSH, a graphical session).

Prerequisites

• snmpd (net-snmp) running on the host, listening on an address the poller reaches (UDP 161), with the firewall open to the poller only.
• The view granted to the poller includes hrSystem (.1.3.6.1.2.1.25.1), which most default configurations already allow.
• Read-only access, SNMPv2c or SNMPv3, set on the host or one of its folders (protocol:snmp:* variables).

# /etc/snmp/snmpd.conf
agentaddress udp:161
view   banshee included .1.3.6.1.2.1.25.1
rocommunity <community> 192.0.2.10 -V banshee
# or: rouser <user> priv -V banshee

Outputs

Watches

Limits

• What is normal depends on the server, a jump host or a server nobody logs into: the watch has no default threshold.
• A session that does not write to utmp (a command run over SSH without a terminal, an automation tool) is not counted.