Q:

Set up a serial port with VirtualBox on Ubuntu (guest OS : Windows XP)

I'm having trouble for a few weeks now trying to access the serial port of my computer when working on the guest OS Windows XP Pro via VirtualBox. The host OS is Ubuntu 10.04 LTS and I'm using VirtualBox 5.0.18. In its settings, I've set up the serial port as on this screenshot:

...but then I can't run the virtual machine:

I've already asked the VirtualBox forum but they replied it was more a Ubuntu problem than a VB one, so I'm asking for help here! 
The thing I'm trying to do is to back up an old device (from the early 2000s or late 1990s), which back-up software can only be opened on Windows. I've managed to install and open it on my XP guest OS, but it cannot communicate with the peripheral device.
Excuse me if I'm not always intelligible, I'm not used to run Ubuntu and I'm French, so my English may not be perfect!
Thanks in advance though :)
Lucas

A:

Your user is not in the group that has access the serial port. You can either run Virtualbox as root (Not recommended ), or add your user to the group.
sudo usermod -a -G dialout <username>

You might have to logout and login again to make this work.
Cheers

A:

First check the actual permissions on your host system. Something like:
~ ls -l /dev/ttyS0
Mine is:
crw-rw---- 1 root dialout 4, 64 2016-05-24 07:34:52 /dev/ttyS0
This means thay either I need to be root (first 'rw-' from left) or I need to be in the dialout group (second 'rw-' from left).
Try from command line a check with command id like:

~ id
uid=1000(enzo) gid=1000(enzo) groups=1000(enzo),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),113(lpadmin),127(sambashare)

In this case I cannot access that serial port. So I can add myself to dialout group:

~ sudo usermod -a -G dialout enzo

where enzo is your very userid as shown above by command id
Then you need to logout and log back in in orderto have this change effective.

