[CentOS] Help with writing a udev rule

Wed May 2 16:54:40 UTC 2012
Robert Heller <heller at deepsoft.com>

At Wed, 2 May 2012 16:27:48 +0000 CentOS mailing list <centos at centos.org> wrote:

> Can someone please help me with writing a udev rule?
> I need /dev/ttyUSB0 to automatically have 777 rights when plugged in.  I'd like it to only apply to that one specific device.
> I'm not sure where to start, what files to look at and also what to write to make it work.

Does this give you a clue:

sauron.deepsoft.com% cat /etc/udev/rules.d/10-local.rules
#KERNEL="ttyS0", SYMLINK="mouse"
#KERNEL="mice",          NAME="input/%k",SYMLINK="mouse"
KERNEL=="ttyS4", SYMLINK="modem"
KERNEL=="ttyS5", SYMLINK="back", MODE="0666"
KERNEL=="ttyS7", SYMLINK="front", MODE="0666"
#KERNEL=="sr[0-9]*", GROUP="disk", MODE="0666"
#KERNEL=="scd[0-9]*", GROUP="disk", MODE="0666"
#KERNEL=="hd[a-z]", BUS=="ide", SYSFS{removable}=="1",
PROGRAM=="check-cdrom.sh %k DVD", SYMLINK+="dvdrom"
KERNEL=="sd[a-z]*", BUS=="scsi", SYSFS{vendor}=="Kingston", NAME="thumb"

Things to note: '/dev/ttyUSB0' is probably not a good name (I get away
with ttyS4, ttyS5, and ttyS7, since these are not hotplugable devices
(they are on a 4 port PCI card).  Anything subject to hot pluging (like
my Kingston thum drive), should probably be using a NAME or SYMLINK
directive and be testing on something like a SYSFS{vendor} or something.
Each time you plug it in the name could change, depending on what else
is plugged in at the time.

You probably want something like:

KERNEL=="ttyUSB*", BUS=="usb", SYSFS{vendor}=="whatever", MODE="0777", SYMLINK="USBSerialPort"

Put this in /etc/udev/rules.d/10-local.rules

Replace 'whatever' with the vendor name or use SYSFS{idVendor} and the
hex code, possibly also with a SYSFS{idProduct} test as well. You can
find out what works for the SYSFS keys by looking in
/sys/bus/usb/devices/usb*/* -- the keys are the names of the files and
the values to test for are the contents of these 'files'.

> Brad
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Robert Heller             -- 978-544-6933 / heller at deepsoft.com
Deepwoods Software        -- http://www.deepsoft.com/
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