This error means that snmptranslate couldn’t find a needed MIB file (DISMAN-EXPRESSION-MIB.txt).
I assume if you added this MIB to the search path it would work, but I looked over the example configs and saw the example where we use DISMAN-EXPRESSION-MIB::sysUpTimeInstance. I don’t have this MIB on my system either but I do have the similar DISMAN-EVENT-MIB::sysUpTimeInstance. If you are trying to run this example then maybe just switch out the MIB name:
[[inputs.snmp.field]]
name = "uptime"
- oid = "DISMAN-EXPRESSION-MIB::sysUpTimeInstance"
+ oid = "DISMAN-EVENT-MIB::sysUpTimeInstance"