hyperledger/fabric · error

error writing config update to output

Error message

error writing config update to output

What it means

After successfully marshaling the computed ConfigUpdate, computeUpdt writes the bytes to the user-specified output file. If that write fails (disk error, bad path, permissions), this wrapped error is returned. It indicates an I/O problem with the output destination, not a config computation problem.

Source

Thrown at cmd/configtxlator/main.go:230

	if err != nil {
		return errors.Wrapf(err, "error unmarshalling updated config")
	}

	cu, err := update.Compute(origConf, updtConf)
	if err != nil {
		return errors.Wrapf(err, "error computing config update")
	}

	cu.ChannelId = channelID

	outBytes, err := proto.Marshal(cu)
	if err != nil {
		return errors.Wrapf(err, "error marshaling computed config update")
	}

	_, err = output.Write(outBytes)
	if err != nil {
		return errors.Wrapf(err, "error writing config update to output")
	}

	return nil
}

View on GitHub (pinned to 2736b63f8f)

Solutions

1. Check the wrapped OS error: create the output directory if missing (e.g. mkdir -p).
2. Verify write permissions on the output location for the user running configtxlator.
3. If output is a directory, supply a file path instead.
4. Check disk space/quota (df -h) if in CI or a container.

Example fix

// before
configtxlator compute-update --original cfg.pb --updated upd.pb --channel myc --output /nonexistent/out.pb
// after
mkdir -p /tmp/config && configtxlator compute-update --original cfg.pb --updated upd.pb --channel myc --output /tmp/config/out.pb

outPath := "/tmp/config/out.pb"
if err := os.MkdirAll(filepath.Dir(outPath), 0o755); err != nil {
    log.Fatal(err)
}
if info, err := os.Stat(outPath); err == nil && info.IsDir() {
    log.Fatalf("%s is a directory, need a file path", outPath)
}

When it happens

Trigger: Running 'configtxlator compute-update --output <path>' where the path is in a non-existent directory, is not writable, is a directory itself, or the disk is full.

Common situations: Typo in --output path; read-only filesystem or container; output path pointing at a directory; no permission to write in the target dir; disk quota exceeded in CI.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• failed writing file %s: %v
• error writing output
• error reading input
• error encoding output
• error reading original config

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/fb2f062d58680e87. Report an issue: GitHub.