Template:FAQ:Agent 42

This device is normally restricted to just being accessible by root (or possibly by a special group such as 'kmem' or 'sys'). The agent must be able to read this device to obtain the necessary information about the running system.

Check that the agent was started by root, and is running with UID 0 (or suitable GID if appropriate). The agent will normally continue to run without this level of access permission, but won't be able to report values for many of the variables (particularly those relating to network statistics).