Influencing Kernel Device Event Handling With Udev Rules - Novell LINUX ENTERPRISE SERVER 10 - INSTALLATION AND ADMINISTRATION 04-08-2006 Installation Manual

The UEVENT lines show the events the kernel has sent over netlink. The UDEV lines
show the finished udev event handlers. The timing is printed in microseconds. The time
between UEVENT and UDEV is the time udev took to process this event or the udev
daemon has delayed its execution to synchronize this event with related and already
running events. For example, events for hard disk partitions always wait for the main
disk device event to finish, because the partition events may rely on the data the main
disk event has queried from the hardware.
udevmonitor --env shows the complete event environment:
UDEV [1132633002.937243] add@/class/input/input7
UDEV_LOG=3
ACTION=add
DEVPATH=/class/input/input7
SUBSYSTEM=input
SEQNUM=1043
PHYSDEVPATH=/devices/pci0000:00/0000:00:1d.1/usb2/2-2/2-2:1.0
PHYSDEVBUS=usb
PHYSDEVDRIVER=usbhid
PRODUCT=3/46d/c03e/2000
NAME="Logitech USB-PS/2 Optical Mouse"
PHYS="usb-0000:00:1d.1-2/input0"
UNIQ=""
EV=7
KEY=70000 0 0 0 0 0 0 0 0
REL=103
udev also sends messages to syslog. The default syslog priority that controls which
messages are sent to syslog is specified in the udev configuration file /etc/udev/
udev.conf. The log priority of the running daemon can be changed with
udevcontrol log_priority=level/number.
25.6 Influencing Kernel Device Event
Handling with udev Rules
A udev rule can match any property the kernel adds to the event itself or any information
that the kernel exports to sysfs. The rule can also request additional information from
external programs. Every event is matched against all provided rules. All rules are lo-
cated in the /etc/udev/rules.d directory.
Every line in the rules file contains at least one key value pair. There are two kinds of
keys, match and assignment keys. If all match keys match their values, the rule is applied
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