Ubuntu 14.04 password lost and can't change boot order

I loaded up a little Intel NUC with Ubuntu 14.04 via a USB drive. I must have messed up the password to the default user because it's not working when the system goes to screen saver mode. I was going to just blast it with a new image. But now it seems to be insisting on booting to the internal hard drive (mSATA) and bypassing the bootable USB. Need help with either recovering the password or getting the thing to boot from the USB instead of the hard drive. Thank you.
amigan_99Network EngineerAsked:
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Set the BIOS to boot from the USB. If that doesn't work it might be because the USB drive is unbootable. Simply saving data/... on an USB drive doesn't mean it is bootable too.
Ubuntu usually has repair options in the boot menu, from which you can boot into single mode and then change the user password. When booting press ESC to get to the grub boot menu, and then you should be able to select the repair mode.

If there is no such option in the boot menu, press e to temporarily edit the boot menu, then select the line where it says "quiet splash" and behind that type "single". After that you should be able to boot into single mode and change the password.
Try this:

Stop the system at the boot menu
hit 'e' to Edit  the entry

Go down to edit the second line that starts with 'kernel'
hit 'e' to Edit the line

add  init=/bin/sh
to the end of the line
press enter
press 'b' for boot

after the system boots
use the commands
# mount -o remount,rw /
# passwd NameOfYourUser

Type new password.

# mount -o remount,ro /

Reboot system.
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Gerwin Jansen, EE MVETopic Advisor Commented:
Press SHIFT while booting to get in to the Grub menu, choose 'Advanced ..' and then the '... recovery' option. From the recovery menu, choose the 'root' prompt item. Then as root change the password of your user account using 'passwd <useraccount>'. Reboot and logon with your user account.
amigan_99Network EngineerAuthor Commented:
Having no luck getting to grub menu. I tried Shift-power on and Esc-power on. Ending up at the gui.
Gerwin Jansen, EE MVETopic Advisor Commented:
But you can get into BIOS using F2 key?

To get into GRUB menu, just reboot and try pressing SHIFT a few times, instead of keeping it pressed, system may think the keyboard is stuck.
Press esc after powering on, and after post is finished.
Press the appropriate key being shown on screen to enter in BIOS or select boot options and then select the  boot device you want to go with..

Post you can directly modify system's shadow file for removing encrypted password of root else by pressing keys multiple times you need to move at grub menu and then need to try what above had mentioned.

Usually you can press the following keys to enter BIOS and change boot order to USB:

Dell: F12 or F2
HP: F10 or F12 or F1
Lenovo: F12 or F2
Phoenix BIOS: DEL

When cold booting the machine, press and hold the key for 2 seconds, then briefly lift the key very quickly and then press it again 2 secs, repeat until BIOS is entered or if it didn't work, cold boot the machine again and try another key.
Gerwin Jansen, EE MVETopic Advisor Commented:
Intel NUC has F2 afaik

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amigan_99Network EngineerAuthor Commented:
Sorry - haven't been able to get back on this. Will try F2 tonight. But now I have found some threads where people can not get to the bios of the NUC in general. Some folks recommended trying a different monitor. ?? I have it attached to my HD TV as I want to use this as a media center once I finally get things going.

Gerwin Jansen, EE MVETopic Advisor Commented:
Seen those threads as well, what is your NUC device exactly? Does it have another video output than just HDMI? Can you test (maybe with a neighbor or friend) another HDMI display, like a computer monitor? NUC is easy to carry around ;)
amigan_99Network EngineerAuthor Commented:
The NUC is model DCCP847DYE. F2 got me to bios GUI and in there I saw the USB was no longer checked as a boot device. Not sure why that was the case as I was must have booted off USB originally in order to load Ubuntu. Anyhow things are looking up.
amigan_99Network EngineerAuthor Commented:
Ok that did it. Thank you. I am re-imaging from boot USB
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