The HOST-RESOURCES MIB omits Linux tmpfs volumes as part of a long list of "not real" filesystems. Unlike usbfs, sysfs, procs and the rest, however, tmpfs is a "real" filesystem even if only RAM-backed. Many people use tmpfs for /tmp, and some embedded setups have / on a tmpfs. As a result I think there is a valid need to have HOST-RESOURCES report on tmpfs volumes.
I'm attaching a one line patch which will allow this.
Patch for net-snmp-5.4.2.1 HR MIB to report on tmpfs
I also ran into the fact that tmpfs filesystems are not exposed via SNMP. Is that on purpose and if so, why?
This should have been fixed by commit 327079a4ae20e2d4766fe549a6e4e57fbe947bcd ("HOST-MIB, hr_filesys: Also monitor tmpfs").