errno 45 (EL2NSYNC) in Linux: meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: EL2NSYNC is a legacy Linux errno meaning legacy level-2 synchronization lost.

Could be also:
Constant	Type	OS
KERN_RPC_CONTINUE_ORPHAN	Kern return	Mac
ippStsLLADisabled	Intel Ipp Status	Any
ENOTSUP	errno	Mac
EDEADLK	errno	Solaris
SCSI_DISK_DRIVER_INTERNAL	BugCheck Code	Windows

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EL2HLT	ENOTSUP

EL2NSYNC

EL2NSYNC: Linux legacy errno

EL2NSYNC (errno 2) reports that the legacy level-2 communications state is not synchronized. These names come from historical System V/XENIX compatibility interfaces; on modern Linux they usually point to a driver, STREAMS-compatibility layer, or legacy IPC contract rather than a general filesystem error.

Evidence to capture

Record stream/device identity, protocol state, synchronization counters, and last successful event.

Focused test

compare synchronization state before and after a controlled reinitialization of the same stream.

Correction

restore protocol synchronization rather than changing unrelated application data.

Verification

Repeat the original system call and confirm it passes the former EL2NSYNC boundary with the same object identity.

Technical references

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