Debugging the udev event processing
===================================

To visualize the driver core events and the udev event processes, use:
  udevmonitor

it prints:
  UEVENT[1132632714.285362] add@/devices/pci0000:00/0000:00:1d.1/usb2/2-2
  UEVENT[1132632714.288166] add@/devices/pci0000:00/0000:00:1d.1/usb2/2-2/2-2:1.0
  UEVENT[1132632714.309485] add@/class/input/input6
  UEVENT[1132632714.309511] add@/class/input/input6/mouse2
  UEVENT[1132632714.309524] add@/class/usb_device/usbdev2.12
  UDEV  [1132632714.348966] add@/devices/pci0000:00/0000:00:1d.1/usb2/2-2
  UDEV  [1132632714.420947] add@/devices/pci0000:00/0000:00:1d.1/usb2/2-2/2-2:1.0
  UDEV  [1132632714.427298] add@/class/input/input6
  UDEV  [1132632714.434223] add@/class/usb_device/usbdev2.12
  UDEV  [1132632714.439934] add@/class/input/input6/mouse2

UEVENT lines show the events the kernel sends 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 was queued to synchronize it with other events.

If called with:
  udevmonitor --env

it prints the whole 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"


Udev also sends messages to syslog according to the configured debugging
level. Udev specific tools which are called, also respect the setting
of udev_log. But there might be some which need special actions to make
them verbose.

Set  udevs loglevel in the damon at runtime with:
  udevcontrol log_priority=<level>

Enable logging permanently, set (it may make udev _very_ slow):
  udev_log=info in /etc/udev/udev.conf.


For further processing of the logging output you should get a clean logfile at
next boot. Just move the old logfile away. (Syslog will still use the moved file
until it's restarted).

The script 'show_event_log' provided along with this file, can be used to
extract info out of /var/log/messages. Call it:
  show_event_log <first> [<last> [<list of event types>] ]
<first> is the sequence number of the first event you are interested in.
<last>  is the number of the last event. You may write 'last' literally. It may
        also be omitted if you want to see a single event. 
<list>  is a list of event types you like to see. If you omit it, you get most
        events, not all. Some are exclude by default. Use " " as list if you
        want to see really all. Or edit the list of skipped events in the first
        lines of the script

If you don't use /var/log/messages as the logfile you may set the environment
variable MESSAGES=<logfile>.