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fedora-users: Re: Serial port permissions -

Re: Serial port permissions -

From: Bob Goodwin <bobgoodwin_at_nospam>
Date: Tue Oct 18 2011 - 16:21:19 GMT
To: users@lists.fedoraproject.org

On 18/10/11 12:00, Brian Mury wrote:
> On Tue, 2011-10-18 at 11:36 -0400, Bob Goodwin wrote:
>> How do I determine if I have the right serial port
>> permissions, where do I look?
> The serial port device should be owned by root, and belong to the
> dialout group, with both the owner and the group having read and write
> permissions. You can verify this like this:
>
>> ll /dev/ttyS*
> crw-rw---- 1 root dialout 4, 64 Oct 18 01:21 /dev/ttyS0
> crw-rw---- 1 root dialout 4, 65 Oct 18 00:28 /dev/ttyS1
> crw-rw---- 1 root dialout 4, 66 Oct 18 00:28 /dev/ttyS2
> crw-rw---- 1 root dialout 4, 67 Oct 18 00:28 /dev/ttyS3
> crw-rw---- 1 root dialout 4, 68 Oct 18 01:14 /dev/ttyS4
> crw-rw---- 1 root dialout 4, 69 Oct 18 00:29 /dev/ttyS5
> crw-rw---- 1 root dialout 4, 70 Oct 18 01:28 /dev/ttyS6
> crw-rw---- 1 root dialout 4, 71 Oct 18 01:10 /dev/ttyS7
>
> Yeah, I've got a lot of serial ports! :-)
> The column that says "root" is the owner.
> The column that says "dialout" is the group.
> The second and third characters are the owner read/write permissions (r
> or w indicates permission, - indicates no permission).
> The fifth and sixth characters are the group read/write permissions.
>
> You can run "system-config-users" as root, and add your user account to
> the dialout group. You'll need to log that user out and back in after
> making that change.
>
> Brian
>
>

        This is what I see there and it looks ok to me:

            [bobg@box9 ~]$ ll -al /dev/ttyS*
            crw-rw----. 1 root dialout 4, 64 Oct 18 03:14 /dev/ttyS0
            crw-rw----. 1 root dialout 4, 65 Oct 18 03:14 /dev/ttyS1
            crw-rw----. 1 root dialout 4, 66 Oct 18 03:14 /dev/ttyS2
            crw-rw----. 1 root dialout 4, 67 Oct 18 03:14 /dev/ttyS3

        I haven't changed anything in "system-config-users" I've set up
        on a second F-15 computer and still can't see anything toggle on
        DTR or RTS. Perhaps my test method is invalid? I am simply
        looking at the voltage between signal ground and those two
        points at the end of a cable with no termination, it is always a
        high negative value, above 12 volts.

        Bob

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