Take the 2-minute tour ×
Ask Ubuntu is a question and answer site for Ubuntu users and developers. It's 100% free, no registration required.

I had Windows XP on this box and it failed. Thinking it was corrupted OS I tried to reinstall, and it failed. But then I tried to install Ubuntu, and I could not run it from the USB or from the HD.

Did the mem test and found out one of my 512MB sticks (had 2) failed. I removed the bad one and was able to install Ubuntu but it was sluggish.

I was trying to quickly setup my packet radio for Hurricane Sandy. Downloaded the Serial Port Terminal and was able to get some use but the system kept locking up. So Installed Xubuntu next to it, planning on running out the next day to get RAM for the box. Put Xubuntu on and now I am getting the following error with serial port terminal.:

Cannot open /dev/ttyS0: Permission denied

I would like to be able to use serial port terminal, or equivalent with Xubuntu so I can use my kpc3 packet terminal, connect to the com port on the back of my computer.

Any ideas?

share|improve this question

2 Answers 2

The tty devices belong to the "dialout" group, I suspect you are not a member of this group and hence are denied access to /dev/ttyS0, so you need to add yourself to that group.

First check if you are a member of that group:

groups ${USER}

..this will list all the groups you belong to. If you don't belong to the dialout grup then add yourself to it, for example:

sudo gpasswd --add ${USER} dialout

You then need to log out and log back in again for it to be effective. Then see if it fixes your problem.

share|improve this answer

Had a look around various forums and it looks to be a bug related to permissions. Here's how I got around the problem (long version). You WILL need BOTH cu and setserial packages installed.

In three terminal tabs, monitored output from # tail -f /var/log/messages That's how we know if we have a /dev/ttyUSB0 or not.

In the second tab, simply ran a loop to ls -l this device to see it's permissions and it's group ID is 'dialout'. THIS is the critical bit. For some reason, your user MUST use this GID to do the cu, so...

In the third tab, as root, did # newgrp dialout (to correspond with the GID of dialout). Tested with # touch /tmp/anything ... doing ls -l on this file shows it is created by root with a dialout group, so we're ready to ... # cu -l /dev/ttyUSB0 In my case I needed to hit return again to see the expected prompt, in other cases speed may need to be specified.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.