Allow guest serial port to redirect to a pseudo terminal on UNIX hosts

[ziyan]

Currently you can redirect a guest's serial port only to a domain socket or a hardware port (TTY). Connecting to a domain socket requires additional tools like "socat" to transform the vbox domain socket to either a PTY or TCP port.

It would be nice to be able to redirect a guest's serial port *directly* to a pseudo terminal slave device on UNIX hosts. Basically I would like to do something like:

VBoxManage--uartmode1 /dev/ttyp1
screen /dev/ptyp1 && VBoxManage startvm linux

On v 4.1. this fails with Failed to open host device /dev/ttyp1 VERR_RESOURCE_BUSY

A forum thread describing this issue: ​https://forums.virtualbox.org/viewtopic.php?f=2&p=101962

I hope adding this is not too difficult since you already support TTYs. Thanks.

[aeichner]

This works here on an OS X host. The only problem is that I received a warning because pseudo terminals don't support TIOCMGET. This will be fixed in the next maintenance release where we just skip querying the status lines for pseudo terminals.

Can you confirm that this works for you with a recent VirtualBox release leaving the above mentioned warning aside?

[Valery Ushakov]

It failed most likely b/c the master side was not open. And since ~everyone has switched to the cloning sysv ptys that approach won't work there either as the ptys don't even exist until you clone yourself a master/slave pair. What you can do instead is use a script that you'd run under screen that will use the pty after the screen has created new window.

[Valery Ushakov]

Quick proof of concept script to start vbox with serial port connected to a new screen window