The Correct OID for System Uptime

February 11, 2010 · 1 min read

I use SNMP to track system uptime so I know when hosts have recently rebooted. But I keep making the same mistake: reaching for sysUpTime.0 when I should be using hrSystem.hrSystemUptime.0.

Here's the difference, so I stop tripping over this:

sysUpTime.0: Timeticks (in hundredths of a second) since snmpd started. If someone restarts the SNMP daemon, this resets — even though the machine hasn't rebooted.
hrSystem.hrSystemUptime.0: Timeticks since the hardware started. This is the one you want for actual system uptime.

In short: if you want to know how long the machine has been running, use hrSystem.hrSystemUptime.0. If you want to know how long the SNMP agent has been running, use sysUpTime.0.

These posts are LLM-aided. Backbone, research, original writing, and structure by Craig. Editing by Craig + LLM. Proof-reading by Craig.