{"record":{"id":"821eba518988d95a","repo":"hashicorp/nomad","slug":"error-opening-fifo-parent-directory-q-v","errorCode":null,"errorMessage":"error opening fifo parent directory %q: %v","messagePattern":"error opening fifo parent directory %q: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"client/lib/fifo/mkfifoat.go","lineNumber":22,"sourceCode":"//go:build linux || freebsd || netbsd || openbsd\n\npackage fifo\n\nimport (\n\t\"fmt\"\n\t\"os\"\n\t\"path/filepath\"\n\n\t\"golang.org/x/sys/unix\"\n)\n\nfunc mkfifo(path string, mode uint32) (err error) {\n\tdir := filepath.Dir(path)\n\tbase := filepath.Base(path)\n\n\troot, err := os.OpenRoot(dir)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"error opening fifo parent directory %q: %v\", dir, err)\n\t}\n\tdefer root.Close()\n\n\tparent, err := root.Open(\".\")\n\tif err != nil {\n\t\treturn fmt.Errorf(\"error getting file handle to fifo parent directory %q: %v\", dir, err)\n\t}\n\tdefer parent.Close()\n\n\t// os.Root doesn't support creating a FIFO, so we need to drop to the\n\t// syscall and grab the parent's FD\n\terr = unix.Mkfifoat(int(parent.Fd()), base, mode)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"error creating fifo: %w\", err)\n\t}\n\treturn nil\n}\n","sourceCodeStart":4,"sourceCodeEnd":40,"githubUrl":"https://github.com/hashicorp/nomad/blob/482b49bf1aec006f089bcfc7e632d8f6ac303e5e/client/lib/fifo/mkfifoat.go#L4-L40","documentation":"This mkfifo variant creates FIFOs safely with mkfifoat: it first opens the FIFO's parent directory with os.OpenRoot so the create happens relative to a directory handle (no symlink escape). This error is returned when that parent-directory open fails — the directory does not exist (ENOENT) or is not accessible (EACCES).","triggerScenarios":"Calling fifo.Create(path, mode) on Linux when filepath.Dir(path) does not exist, the process lacks search permission on the directory, or the directory path is invalid/unmounted.","commonSituations":"Log IO setup before the runtime directory is created; typo in configured path; permission drops (container running as non-root user in root-owned dir); path traversal blocked because parent is a symlink to elsewhere.","solutions":["Create the parent directory first: os.MkdirAll(filepath.Dir(path), 0o700)","Verify the directory exists and is writable/searchable by the current user","Fix the configured FIFO path","Check for symlinked parent components that os.Root intentionally refuses to follow"],"exampleFix":"// before\nif err := fifo.Create(\"/run/containerd/io/stdout\", 0o600); err != nil { return err }\n// after\nif err := os.MkdirAll(\"/run/containerd/io\", 0o700); err != nil { return err }\nif err := fifo.Create(\"/run/containerd/io/stdout\", 0o600); err != nil { return err }","handlingStrategy":"validation","validationCode":"dir := filepath.Dir(path)\nif fi, err := os.Stat(dir); err != nil || !fi.IsDir() {\n\treturn fmt.Errorf(\"fifo parent dir %q missing\", dir)\n}","typeGuard":null,"tryCatchPattern":"err := fifo.Create(path, mode)\nif err != nil {\n\tif errors.Is(err, fs.ErrNotExist) {\n\t\tif mkErr := os.MkdirAll(filepath.Dir(path), 0o700); mkErr != nil { return mkErr }\n\t\terr = fifo.Create(path, mode)\n\t}\n\tif err != nil { return err }\n}","preventionTips":["Create parent directories before fifo.Create","Avoid symlinked parents; os.Root refuses to follow them","Validate configured fifo paths at startup","Run with a user that can search/write the parent dir"],"tags":["go","linux","fifo","directory-not-found"],"backgroundTag":"fifo-create-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"}