What does errno 51 (EBADR) in Solaris mean?

EBADR

A request descriptor is not an ordinary file descriptor

EBADR is Solaris errno 51 and is labeled invalid request descriptor. It sits in the historical “convergent error returns” range of the illumos header. The word descriptor should not automatically send debugging toward close(), read(), or an invalid integer file descriptor; EBADF and EBADFD cover different conditions.

Oracle's Solaris Common Messages guide records a concrete historical use: NIS+ used this errno to indicate corrupted or missing tables. That is far more specific than the previous generic “old exchange operation” explanation and shows why the failing subsystem must be identified before interpreting the noun “request”.

What to verify

• Find the API or service that returned this errno and inspect its request-object or table validation path.
• For old NIS+ software, check the relevant table state and accompanying service diagnostics rather than retrying a filesystem operation.
• Keep this errno separate from EBADRQC: the latter identifies an invalid request code, not the request descriptor.

References

• Oracle Solaris intro(2) errno catalog
• Solaris Common Messages and Troubleshooting Guide
• illumos sys/errno.h ABI definitions