boot_speed_up_might_cause_failure

# toggle the following option on seems to be possible to cause net card bringing up failure

# Speed up boot without waiting for settle in udev
#OMIT_UDEV_SETTLE=y

# Speed up boot without waiting for settle in udev_retry
#OMIT_UDEV_RETRY_SETTLE=yes


During the boot script udev, there is a call to udev settle that requires some time to complete. 
This time may or may not be required depending on devices present in the system. 
If you only have simple partitions and a single ethernet card, the boot process will probably not 
need to wait for this command. To skip it, set the variable OMIT_UDEV_SETTLE=y.


The boot script udev_retry also runs udev settle by default. This command is only needed by 
default if the /var directory is separately mounted. This is because the clock needs the file 
/var/lib/hwclock/adjtime. Other customizations may also need to wait for udev to complete, 
but in many installations it is not needed. Skip the command by setting the variable OMIT_UDEV_RETRY_SETTLE=y.