hashicorp/packer · error

could not write final plugin binary file: %w

Error message

could not write final plugin binary file: %w

What it means

InstallLatest has downloaded a plugin binary into a buffer and opened the final destination file in the plugin directory, but writing the buffered bytes to that file failed. The getter treats this as fatal for that plugin requirement and aborts the install. It wraps the underlying OS error, which is the real diagnostic.

Source

Thrown at packer/plugin-getter/plugins.go:919

						}
						return nil, errs
					}

					// create directories if need be
					if err := os.MkdirAll(outputFolder, 0755); err != nil {
						err := fmt.Errorf("could not create plugin folder %q: %w", outputFolder, err)
						errs = multierror.Append(errs, err)
						log.Printf("[TRACE] %s", err.Error())
						return nil, errs
					}
					outputFile, err := os.OpenFile(outputFileName, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0755)
					if err != nil {
						err = fmt.Errorf("could not create final plugin binary file: %w", err)
						errs = multierror.Append(errs, err)
						return nil, errs
					}
					if _, err := outputFile.Write(outputFileData.Bytes()); err != nil {
						err = fmt.Errorf("could not write final plugin binary file: %w", err)
						errs = multierror.Append(errs, err)
						return nil, errs
					}
					outputFile.Close()

					cs, err = checksum.Checksummer.Sum(&outputFileData)
					if err != nil {
						err := fmt.Errorf("failed to checksum binary file: %s", err)
						errs = multierror.Append(errs, err)
						log.Printf("[WARNING] %v, ignoring", err)
					}
					if err := os.WriteFile(outputFileName+checksum.Checksummer.FileExt(), []byte(hex.EncodeToString(cs)), 0644); err != nil {
						err := fmt.Errorf("failed to write local binary checksum file: %s", err)
						errs = multierror.Append(errs, err)
						log.Printf("[WARNING] %v, ignoring", err)
						os.Remove(outputFileName)
						continue
					}

View on GitHub (pinned to eb36e3c3e4)

Solutions

1. Check free disk space on the partition holding the Packer plugins directory (df -h ~/.packer.d) and free space if needed
2. Inspect the wrapped cause (%w) in the full error for ENOSPC/EPERM/EACCES and fix that specific condition
3. Remove the partial plugin file and directory, then re-run `packer init`
4. Ensure the directory permissions allow writes for the user running packer; avoid running with a mismatched user (sudo)
5. Set PACKER_PLUGIN_PATH to a writable location if the default path is restricted

Example fix

// before (running as root then as user leaves mixed-permission files)
sudo packer init .
// after
rm -rf ~/.packer.d/plugins/github.com/broken-plugin
packer init .

import "os"
// before `packer init` in CI:
info, err := os.Stat(pluginDir)
if err != nil || !info.IsDir() {
    return fmt.Errorf("plugin dir %s missing or not writable: %w", pluginDir, err)
}
if err := checkFreeSpace(pluginDir, 500*1024*1024); err != nil { // require 500MB
    return err
}

When it happens

Trigger: outputFile.Write() returns an error during InstallLatest — typically disk full (ENOSPC), permission denied on the newly created file, or I/O error on the target filesystem.

Common situations: Disk quota exhausted in ~/.packer.d/plugins; read-only mount or noexec/immutable file attributes; antivirus or another process locking the freshly created binary; running packer as a user without write access to PACKER_PLUGIN_PATH.

Related errors

• failed to write local binary checksum file: %s
• Checksum: failed to open file for checksum: %s
• ListInstallations: failed to list installed plugins: %s
• could not create plugin folder %q: %w
• could not create final plugin binary file: %w

AI-assisted analysis of hashicorp/packer@eb36e3c3e4 (2026-09-05). Data as JSON: /api/errors/c80552a49853e481. Report an issue: GitHub.