{"record":{"id":"bc95b046155eeb69","repo":"hashicorp/nomad","slug":"failed-to-create-stderr-v","errorCode":null,"errorMessage":"failed to create stderr: %v","messagePattern":"failed to create stderr: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"drivers/shared/executor/executor.go","lineNumber":285,"sourceCode":"\t\t\tf, err := fifo.OpenWriter(c.StdoutPath)\n\t\t\tif err != nil {\n\t\t\t\treturn nil, fmt.Errorf(\"failed to create stdout: %v\", err)\n\t\t\t}\n\t\t\tc.stdout = f\n\t\t} else {\n\t\t\tc.stdout = nopCloser{io.Discard}\n\t\t}\n\t}\n\treturn c.stdout, nil\n}\n\n// Stderr returns a writer for the configured file descriptor\nfunc (c *ExecCommand) Stderr() (io.WriteCloser, error) {\n\tif c.stderr == nil {\n\t\tif c.StderrPath != \"\" && c.StderrPath != os.DevNull {\n\t\t\tf, err := fifo.OpenWriter(c.StderrPath)\n\t\t\tif err != nil {\n\t\t\t\treturn nil, fmt.Errorf(\"failed to create stderr: %v\", err)\n\t\t\t}\n\t\t\tc.stderr = f\n\t\t} else {\n\t\t\tc.stderr = nopCloser{io.Discard}\n\t\t}\n\t}\n\treturn c.stderr, nil\n}\n\nfunc (c *ExecCommand) Close() {\n\tif c.stdout != nil {\n\t\tc.stdout.Close()\n\t}\n\tif c.stderr != nil {\n\t\tc.stderr.Close()\n\t}\n}\n","sourceCodeStart":267,"sourceCodeEnd":303,"githubUrl":"https://github.com/hashicorp/nomad/blob/482b49bf1aec006f089bcfc7e632d8f6ac303e5e/drivers/shared/executor/executor.go#L267-L303","documentation":"ExecCommand.Stderr() mirrors Stdout(): it lazily opens a FIFO writer at StderrPath to stream task stderr. If fifo.OpenWriter on the stderr path fails, the error is wrapped with this message and Launch fails.","triggerScenarios":"Launch() calls command.Stderr() and fifo.OpenWriter(c.StderrPath) errors — missing fifo, permission denied, or path deleted between stdout and stderr opens.","commonSituations":"Same as stdout fifo failures: allocation dir permission problems, premature cleanup, MAC policy (SELinux) denials, disk full preventing pipe allocation is rare but possible.","solutions":["Verify the stderr fifo exists in the alloc dir; restart the allocation if missing","Correct ownership/permissions on the alloc/log directories","Check audit logs for SELinux/apparmor denials on the path","Compare with the stdout error — if both fail, the alloc dir is the problem"],"exampleFix":"// before\n// SELinux: 'denied { write } for comm=nomad path=.../stderr.fifo'\n// after\n// semanage fcontext -a -t container_file_t '.../stderr.fifo' && restorecon -v .../stderr.fifo","handlingStrategy":"try-catch","validationCode":"func stderrFifoReady(path string) error {\n  fi, err := os.Stat(path)\n  if err != nil { return fmt.Errorf(\"stderr fifo missing: %w\", err) }\n  if fi.Mode()&os.ModeNamedPipe == 0 { return fmt.Errorf(\"%s is not a fifo\", path) }\n  f, err := os.OpenFile(path, os.O_WRONLY, 0)\n  if err != nil { return err }\n  f.Close()\n  return nil\n}","typeGuard":null,"tryCatchPattern":"if err := launchTask(); err != nil {\n  if strings.Contains(err.Error(), \"failed to create stderr\") {\n    log.Printf(\"stderr fifo broken: %v — check alloc dir perms\", err)\n    return restartAllocation()\n  }\n  return err\n}","preventionTips":["Verify fifo writability before deploying permission changes","Consistent UID/GID between client and executor users","Audit MAC (SELinux) policy changes affecting alloc dirs","Monitor alloc-dir tampering by external log shippers"],"tags":["fifo","stderr","streaming","nomad-executor"],"backgroundTag":"fifo-open-failed","analyzedSha":"482b49bf1aec006f089bcfc7e632d8f6ac303e5e","analyzedAt":"2026-09-04T07:54:14.808Z","contentChangedAt":"2026-09-04T07:54:14.808Z","schemaVersion":2},"datasetVersion":"2026-09-08T10:18:20.063Z"}