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Creating an Account with some root permissions

Posted on 2000-03-01
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Last Modified: 2013-12-16
Hi there,

I'm using linux to communicate with external devices by serial or parallel ports. However, I must be root or set root permissions to my prog for accessing to these io ports. What I would like is to create an account which has root permissions for io ports but not for the rest such as accessing in Write mode to system files or accessing to /root directory.

How could I do this ?
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Question by:daanen
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by:bcoleman
ID: 2573403
All you have to do is change ownership and permission for the /dev/{whatever port} to the user.  What you might want to do is set up a group which have permission to access the ports and put those users who need access in that group.
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Expert Comment

by:jyu_88
ID: 2573595
alternatively, you can use 'sudo' program to explicitly grant certain user/group to run a single program/a set of programs as root.
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Reinier earned 20 total points
ID: 2597141
Or you can create a special group for these devices. Say you want to give rw access to /dev/ttyS3 and /dev/ttyS4. Then you add a new group named "devusers" or whatever in /etc/group and /etc/gshadow, like this:

groupadd -g 300 devusers

The exact name and group numerical id are not important, but they must be unique. Next you have to add root and all usernames of the users that must acces the device, to this group. You can do this by hand-editing /etc/group, but you can probabely also use linuxconf or whatever setuptool that comes with your distro.

Then go to /dev, do

chown root:devusers ttyS[34]
chmod 664 ttyS[34]

and you're set.
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Author Comment

by:daanen
ID: 2599453
Thanks for these answers. As I'm the unique user of my linux box, I just chmod 666 /dev/ttyS*. But in the future, I'll probably use Reinier's solution
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