Serial port permissions -

Brian Mury brianmury at alumni.uvic.ca
Tue Oct 18 16:00:16 UTC 2011


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




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