I'm trying to work out how to set up a custom udev rule to override permissions on serial ports (/dev/ttyS* and /dev/ttyUSB*) on CentOS 5.3
The default rule, in /etc/udev/rules.d/50-udev.rules has the line:
KERNEL=="tty[A-Z]*", NAME="%k", GROUP="uucp", MODE="0660"
and I would like the mode to be 0666
Various docs on web say that you shouldn't change 50-udev.rules, but instead create a new rule file that appears lexically before that rule - so I've created a file that contains the line:
KERNEL=="tty[A-Z]*", NAME="%k", GROUP="uucp", MODE="0666"
called 10-local.rules
However, this doesn't work ... the /dev/ttyS* device files get the 'default' owner/group/perms (mode = '0600', uid = '0', gid = '0')
If I rename the 10-local.rules to say 99-local.rules, then the device files get the owner/group/perms from 50-udev.rules (mode = '0660', uid = '0', gid = '14')
I can get the mode set to 0666 by editing 50-udev.rules, however this seems wrong as you should be able to override the defaults without doing this.
Anyone know if this is possible?
Thanks
James Pearson
On Tue, 2009-07-14 at 17:52 +0100, James Pearson wrote:
I'm trying to work out how to set up a custom udev rule to override permissions on serial ports (/dev/ttyS* and /dev/ttyUSB*) on CentOS 5.3
The default rule, in /etc/udev/rules.d/50-udev.rules has the line:
KERNEL=="tty[A-Z]*", NAME="%k", GROUP="uucp", MODE="0660"
and I would like the mode to be 0666
Various docs on web say that you shouldn't change 50-udev.rules, but instead create a new rule file that appears lexically before that rule - so I've created a file that contains the line:
KERNEL=="tty[A-Z]*", NAME="%k", GROUP="uucp", MODE="0666"
called 10-local.rules
However, this doesn't work ... the /dev/ttyS* device files get the 'default' owner/group/perms (mode = '0600', uid = '0', gid = '0')
If I rename the 10-local.rules to say 99-local.rules, then the device files get the owner/group/perms from 50-udev.rules (mode = '0660', uid = '0', gid = '14')
I can get the mode set to 0666 by editing 50-udev.rules, however this seems wrong as you should be able to override the defaults without doing this.
Anyone know if this is possible?
It seems like it should be. I presume that you have already been reading the rules guide found on your system at /usr/share/doc/udev-095/writing_udev_rules/index.html. I can't add much to that, except to point out that to support various models of UPS on different systems, I have put the following into a file named /etc/udev/rules.d/99-nut-ups.rules and gotten the desired results:
# Serial device for UPS monitoring KERNEL=="ttyS0", OWNER="nutdev", GROUP="nut", MODE="0660" KERNEL=="hiddev0", OWNER="nutdev", GROUP="nut", MODE="0660"
As you will note, these lines change the user and group ownership of the target files, but the permissions via the "MODE" parameter should work the same way.
I'm wondering if you might want to try a more selective target for the device in the "KERNEL" parameter, say "ttyS*" since you're targeting your serial ports.
Thanks
James Pearson _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Ron Loftin wrote:
It seems like it should be. I presume that you have already been reading the rules guide found on your system at /usr/share/doc/udev-095/writing_udev_rules/index.html. I can't add much to that, except to point out that to support various models of UPS on different systems, I have put the following into a file named /etc/udev/rules.d/99-nut-ups.rules and gotten the desired results:
# Serial device for UPS monitoring KERNEL=="ttyS0", OWNER="nutdev", GROUP="nut", MODE="0660" KERNEL=="hiddev0", OWNER="nutdev", GROUP="nut", MODE="0660"
As you will note, these lines change the user and group ownership of the target files, but the permissions via the "MODE" parameter should work the same way.
I'm wondering if you might want to try a more selective target for the device in the "KERNEL" parameter, say "ttyS*" since you're targeting your serial ports.
I think my problem is that I included the 'NAME="%k"' in the line from 50-udev.rules when I copied it to my custom rule file - leaving this out (as per your example) and calling it 99-local.rules - it now works.
Thanks
James Pearson
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James Pearson -
Ron Loftin