What information does the 'ibnodes' command display?

The ibnodes utility is a specialized script within the infiniband-diags suite used for high-level topology mapping. When executed, it scans the InfiniBand subnet and provides a concise list of every active node connected to the fabric, categorized by their type. Specifically, it displays all Host Channel Adapters (HCAs/CA) found in the servers (the "hosts") and all InfiniBand switches. This command is an essential first step in fabric validation after a "bring-up" or expansion because it allows an engineer to quickly verify if the expected number of nodes and switches have successfully joined the fabric. Unlike ibnetdiscover, which provides a verbose and complex output of every port-to-port connection, ibnodes focuses on the identity and type of the devices. This distinction is critical for troubleshooting connectivity; if a server's HCA is missing from the ibnodes list, the engineer knows to investigate the physical link or the local HCA driver state rather than searching through thousands of lines of switch-to-switch cabling data.