rdmacmid

rdmacmid is a user-space daemon associated with the RDMA Connection Manager (rdmacm) stack in Linux-based systems. It provides support for remote direct memory access (RDMA) connection management by coordinating between applications that use the librdmacm API and the kernel RDMA subsystem. The daemon helps establish and manage RDMA connections, handling tasks such as address resolution, route resolution, and the orchestration of connection lifecycle events.

In operation, rdmacmid acts as an intermediary that receives requests from user applications via the librdmacm interface and communicates with the kernel’s RDMA core to perform the necessary steps to create or accept RDMA connections. It forwards asynchronous events and state changes to the appropriate applications and may manage multiple concurrent connection endpoints. By consolidating these duties in a daemon, it enables shared access to RDMA resources across several processes and simplifies event handling for complex communication patterns.

Deployment and usage vary by system. rdmacmid typically runs as a background service on machines with InfiniBand or RoCE hardware and is commonly included with the OpenFabrics Enterprise Distribution (OFED) or other packages that provide librdmacm and related RDMA libraries. Depending on the environment, it may operate as a persistent background process or be integrated into an application’s runtime, with system services or init scripts controlling its lifecycle.

Security and permissions considerations are standard for RDMA components: access to RDMA devices and the rdmacm interface generally requires appropriate privileges, and proper isolation is important in multi-tenant or cluster environments. See also RDMA, InfiniBand, RoCE, librdmacm, and rdma_cm_id for related concepts.