/dev/ttyS0 permission error

[Gilboa Davara]

On Sat, 2006-12-02 at 21:23 -0600, Jay Cliburn wrote:
> I've seen references to this scattered about on the web, but no solutions.
> 
> I installed FC6 on a Dell Inspiron 4000 laptop to use as a serial console for 
> debugging kernel problems.  Whenever I start minicom on the laptop, however, I'm 
> greeted with a permission denied error to /dev/ttyS0.  Sure enough, the perms on 
> ttyS0 are 0660 and I'm not a member of the uucp group:
> 
> crw-rw---- 1 root uucp 4, 64 Dec  1 06:04 /dev/ttyS0
> crw-rw---- 1 root uucp 4, 65 Dec  1 06:03 /dev/ttyS1
> crw-rw---- 1 root uucp 4, 66 Dec  1 06:03 /dev/ttyS2
> crw-rw---- 1 root uucp 4, 67 Dec  1 06:03 /dev/ttyS3
> 
> No problem, I thought -- I'll just gin up a udev rule and set the perms to 0666. 
>   Sorry; doesn't work.  As a matter of fact, it gets worse: perms on ttyS0 go to 
> 0600 root:root as a result of my new local rule.
> 
> Okay, not an ideal solution, but let's modify 50-udev.rules and set the default 
> rule for tty[A-Z]* to MODE="0666".  Nope.  Now they're *all* 0600 root:root.
> 
> Here's the rule:
> KERNEL=="ttyS0", NAME="%k", GROUP="uucp", MODE="0666"
> 
> I had no problems with this under Debian Etch and Knoppix Live running on the 
> same laptop.  Debian was running a 2.6.17 kernel, and for the life of me I can't 
> remember the Knoppix kernel version (the web site says 2.6.x -- big help), and I 
> don't have the CD here at home.
> 
> The current workaround is to add non-root users to the uucp group.  (Or maybe 
> this is the solution?)  Any ideas why I can't get a udev rule to change the 
> perms to 0666 on /dev/ttyS0?
> 
> Thanks,
> Jay
> 
> 

Why not solve the problem using the uucp group? It's the designed
solution?

- Gilboa