"Unable to detach from controlling tty (errno=25 Not a tty)"

[christianinsert]

I get quite often the error Unable to detach from controlling tty (errno=25 Not a tty). I could not find any documentation about this. What does it mean? Should I be worried? What can I do to fix it?

[asottile]

this message is normal in verbose mode -- it is a debug message showing that it is not attached to a tty

$ echo hi | dumb-init --verbose echo hello
[dumb-init] Unable to detach from controlling tty (errno=25 Inappropriate ioctl for device).
[dumb-init] Child spawned with PID 37933.
[dumb-init] Unable to attach to controlling tty (errno=25 Inappropriate ioctl for device).
[dumb-init] setsid complete.
hello
[dumb-init] Received signal 17.
[dumb-init] A child with PID 37933 exited with exit status 0.
[dumb-init] Forwarded signal 15 to children.
[dumb-init] Child exited with status 0. Goodbye.

[christianinsert]

Thanks for the info! (If more people get confused about that it might be worth adding to the docs?)

[asottile]

I'm not sure why one would be confused -- it's only there in --verbose mode, it's not messaged as an error, it doesn't terminate the process.