How can I log in to Ubuntu using a USB serial port?

Question

How can I enable remote terminal log in into Ubuntu 9.10 (Karmic Koala) using a USB serial port?

I created device /dev/ttyUSB0, and I want to allow logins using HyperTerminal.

I found some resources, but they are related to real hardware RS-232 ports. I can't find any information about a USB converter.

So far I have established connection between that USB-serial port and my laptop. I can send text to the port (cp sometext.txt /dev/ttyUSB0) and read it using HyperTerminal.

What do I need to do to enable logins on this port?

Answer 1

See the Ubuntu Serial Console HowTo. You'll need to adapt it for your hardware -- instead of ttyS0, which is the first hardware serial port, you'll need to use ttyUSB0. An example of this is below.

---

At minimum, you need to configure upstart to start a getty on that port.

1. Create /etc/init/ttyUSB0.conf and paste the following into it:

   # ttyUSB0 - getty on USB serial port
   #
   # This service maintains a getty on ttyUSB0 from the point the system is
   # started until it is shut down again.
   
   start on stopped rc RUNLEVEL=[2345]
   stop on runlevel [!2345]
   
   respawn
   exec /sbin/getty -L 115200 ttyUSB0 vt102
   

2. Start the getty:

   sudo start ttyUSB0
   

Older Ubuntu versions and distributions that don't use upstart do this by adding a line in /etc/inittab.

This doesn't consider changes to the bootloader configuration to allow Grub to talk to the serial port; refer to the HowTo for details. I'm not sure if Grub can talk to a USB serial port or if that's limited to hardware ports.

Answer 2

Better approach in Ubuntu 12.04:

start on (tty-device-added ttyUSB0)
stop on (runlevel [!2345] or tty-device-removed ttyUSB0)

respawn
exec /sbin/getty -L 115200 ttyUSB0 vt102

• starting getty when hot plugging in ttyUSB0
• stop getty when hot plugging out ttyUSB0