/dev/ttyS0 permission failure in user

clem_g · 06-01-2007, 06:02 PM

Gtkterm uses the serial port /dev/ttyS0 ( COM1 in DOS / Windows ), I am only able to use this in ROOT. When loged on as user - fails to open /dev/ttyS0.

I have used the command:
sudo chmod a+w+r /dev/ttyS0 from ROOT and then it works, however when I reboot the machine I have to do this again.

Q - How can I permanently set the permission so that I do not have to run this command from ROOT every time I reboot?

I am using Fedora Core 5.

Sorry I am new to Linux and this forum
Clem.

ScottSmith · 06-01-2007, 07:16 PM

I am using Debian and if I add myself to the 'dialout' group I get the permission to use the device. I am not sure if this true for Red Hat, but worth a try. It might even be a different group; you can check what group uses /dev/ttyS? by typing in a terminal window ll /dev/ttyS?.

Wim Sturkenboom · 06-02-2007, 01:21 AM

Check the group for /dev/ttyS0 (as said) and make yourself a member of that group. I seem to remember that the group is uucp

clem_g · 06-03-2007, 05:40 PM

How do I make myself a member of the group uucp?

do I edit the file /etc/group and add a line to it?

This group file contains the following lines amongst many other lines

uucp:x:14:uucp
clem:x:500:

my user name is clem

can you advise me what I should put in this file?

Wim Sturkenboom · 06-04-2007, 12:27 AM

Use usermod with the -G option. Read the man page. You can use a graphical tool if X is running on your system (at least, older RHs had that functionality).

ScottSmith · 06-04-2007, 03:21 PM

You can type adduser clem uucp into a terminal window; that should get you the permissions that you need.

forrestt · 06-04-2007, 05:02 PM

you can also edit the /etc/group file and change the uucp entry to:

uucp:x:14:uucp,clem

Wim Sturkenboom · 06-05-2007, 01:22 AM

Quote:

Originally Posted by ScottSmith

You can type adduser clem uucp into a terminal window; that should get you the permissions that you need.

adduser creates a new account by asking questions, or am I mistaken and can it be used to nodify it as well?

ScottSmith · 06-05-2007, 02:03 AM

If used as adduser <username> it will create a new user and asking questions about the user. However, if used as adduser <username> <group> will add <username> to the specified <group>.

Conversely you can use deluser <username> to remove/delete a user from the system. Also deluser <username> <group> to remove a user from a group.

jaepi · 06-05-2007, 02:30 AM

chmod 777 dev/ttyS0

Wim Sturkenboom · 06-05-2007, 05:23 AM

That's not the way as it opens it up for the whole world and, as stated in the opening post, it is no longer there after a reboot.

helptonewbie · 06-05-2007, 06:04 AM

you could if you wanted to change the permissions set it to do so in /etc/rc.d/local.rc, and put your command in there on a new line it will be run as root anyway. Your probably better off however setting your user as part of the group, better security