EC
EREMOTEIO
Linux / POSIXERRORNotableNetworkHIGH confidence

Remote I/O Error

Production Risk

High — indicates remote storage failure; investigate server disk health immediately.

What this means

EREMOTEIO (errno 121) is returned when a remote I/O error occurs, typically from NFS or a network-backed block device when data cannot be read or written due to a remote failure.

Why it happens
  1. 1NFS server returned an I/O error
  2. 2Network-attached storage device failure
  3. 3Remote disk error on NFS server
How to reproduce

NFS read when the server has a disk error.

trigger — this will error
trigger — this will error
ssize_t n = read(nfs_fd, buf, sizeof(buf));
// Returns -1, errno = EREMOTEIO when server has I/O error

expected output

read: Remote I/O error (EREMOTEIO)

Fix

Check NFS server disk health

WHEN When EREMOTEIO is returned on NFS operations

Check NFS server disk health
# Check server-side disk health (run on NFS server)
smartctl -a /dev/sda
dmesg | grep -i "i/o error"
# Check NFS server logs
journalctl -u nfs-server

Why this works

EREMOTEIO originates on the server; investigate server disk and system logs.

Sources
Official documentation ↗

Linux Programmer Manual errno(3)

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