I have noticed that when I unplug the network cable, system waits about 100 seconds to configure the network, So I edited /etc/init/failsafe.conf and comment two wait() lines (thanks to tutorial here)

# Plymouth errors should not stop the script because we *must* reach

# the end of this script to avoid letting the system spin forever

# waiting on it to start.

    $PLYMOUTH message --text="Waiting for network configuration..." || :

    #sleep 40



    $PLYMOUTH message --text="Waiting up to 60 more seconds for network configuration..." || :

    #sleep 59

    $PLYMOUTH message --text="Booting system without full network configuration..." || :

Then I grab a timer and start counting seconds of boot time, the odd thing is it takes 15 more seconds to boot a system with an unplugged network cable that a system with a plugged network cable. and most of the delay is in this line that appears on start up :

the disk driver for servername--vg-swap1 not ready

My home folder is encrypted and Ubuntu has been installed with LVM.

Maybe you say "so what harm can come from 15 more seconds of delay?" Well, I am configuring this server to be used in a traffic control system and in case of power failure the system should be back on its feet as soon as possible, so every second counts.

Thank you.