kovidgoyal/kitty · error

Failed to create SHM file with error: %w

Error message

Failed to create SHM file with error: %w

What it means

RunSSHAskpass serializes the askpass request into shared memory using shm.CreateTemp('askpass-*'). If CreateTemp fails (typically /dev/shm unavailable or not writable), this fatal error is returned.

Source

Thrown at kittens/ssh/askpass.go:132

						fmt.Println(code)
						return 0
					}
				}
			}
		}
	}
	q := map[string]any{
		"message":     msg,
		"type":        q_type,
		"is_password": !is_fingerprint_check,
	}
	data, err := json.Marshal(q)
	if err != nil {
		return fatal(err)
	}
	data_shm, err := shm.CreateTemp("askpass-*", uint64(len(data)+32))
	if err != nil {
		return fatal(fmt.Errorf("Failed to create SHM file with error: %w", err))
	}
	defer data_shm.Close()
	defer func() { _ = data_shm.Unlink() }()

	data_shm.Slice()[0] = 0
	if err = shm.WriteWithSize(data_shm, data, 1); err != nil {
		return fatal(fmt.Errorf("Failed to write to SHM file with error: %w", err))
	}
	if err = data_shm.Flush(); err != nil {
		return fatal(fmt.Errorf("Failed to flush SHM file with error: %w", err))
	}
	trigger_ask(data_shm.Name())
	for {
		time.Sleep(50 * time.Millisecond)
		if data_shm.Slice()[0] == 1 {
			break
		}
	}

View on GitHub (pinned to 6d5d0c4406)

Solutions

1. Ensure /dev/shm exists and is writable (mount tmpfs on it)
2. Increase /dev/shm size (docker --shm-size)
3. Free space if /dev/shm tmpfs is full
4. Avoid running the ssh kitten askpass inside restricted sandboxes

if st, err := os.Stat("/dev/shm"); err != nil || !st.IsDir() { /* fail early with clear message */ }

When it happens

Trigger: Running the ssh kitten askpass helper in an environment where POSIX shared memory is missing: containers without /dev/shm, restricted sandboxes, or tmpfs full.

Common situations: Docker containers with a tiny or absent /dev/shm, chroots, systems with noexec/ro /dev/shm mounts.

Related errors

• Failed to write to SHM file with error: %w
• Failed to flush SHM file with error: %w
• Failed to read from SHM file with error: %w
• Failed to parse response data: %#v with error: %w
• Incorrect owner on pwfile: uid={shm.stats.st_uid} gid={shm.s

AI-assisted analysis of kovidgoyal/kitty@6d5d0c4406 (2026-08-27). Data as JSON: /api/errors/0b61c1038b40e70c. Report an issue: GitHub.