Bash on Ubuntu on Windows - rlwrap could not open master pty

Question

After installing Bash on Ubuntu on Windows, I'm receiving an error from any rlwrap command.

root@localhost:~# rlwrap ls
rlwrap: Could not open master pty: No such file or directory

I've made sure that /dev/ptmx has the correct permissions

root@localhost:~# ls -ld /dev/ptmx
crw-rw-rw- 1 root tty 5, 2 Apr  9 22:44 /dev/ptmx

Yet I still can't get it working. Am I the only one encountering this error? Any help would be greatly appreciated.

Answer 1

Windows Subsystem for Linux (WSL) doesn't (yet?) have a working pty implementation. I suspect that opening /dev/ptmx always fails for this reason, even though the device file exists and has the right permissions.

rlwrap, but also programs like screen and tmux, are never going to work without a pty device. They fail under WSL for the same reason as rlwrap.

Hans (rlwrap maintainer)

Answer 2

I just had the same issue on my Ubuntu 16.04. Purging and re-installing rlwrap solved the problem for me.

sudo apt-get purge rlwrap
sudo apt-get install rlwrap

Of course this is a bit of a different issue because it's not exactly WSL.