Sat, 29 Dec 2018 19:39:30 -0600
> Date: Sat, 29 Dec 2018 14:03:28 -0600
> From: Danny Johnson <bunjee50 at gmail.com>
> To: TCLUG Mailing List <tclug-list at mn-linux.org>
> Subject: [tclug-list] change password
> Message-ID:
> 	<CANa+X+v175fJUbDkGzq31aNWdvYFt-ujU1wygjxeiW6fA97hHA at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
> 
> Hello!
> I can't get in to my terminal because it will not recognize my password.
> I am using Ubuntu 18.04.
> All was well then - BAMM!!!
> Really frustrating.
> Please advise.
> 
> Dan J.
> Newbie

I don't use ubuntu but this has worked on every other distro I have
used.
You could try this.
At the grub boot menu you should see:

Ubuntu
Ubuntu Advanced Options

Look under Advanced options for 'single user mode' or 'recovery console'
or similar. If available boot into that and skip down to "You should
now be in a console..."

If one of those is not available then go back to main menu and type e
to edit command line.
Look for line starting with either 'linux' or 'kernel' and add this to
end of line:

init=/bin/sh

then allow to boot.

You should now be in a console with a prompt.
Type mount
Look for line in output that says:
/dev/sda* on / ... (rw ...)
or
<uuid on> / ... (rw ...)  <- uuid looks like random characters

The important part here is the (rw ...) part. If it says 'ro' instead
of 'rw' you'll have to remount the file system as writable

mount -o remount,rw /

Then type

vi /etc/shadow

If vi is not available try vim.
Look for line with your user name and use arrow keys to put cursor
under first character in second field

dan:jflsjfljfslleie:::
       ^
then use the 'x' key to delete everything to next colon.
type
:wq
to exit vi/vim

Reboot
Login with no password  and then set a new one.

hth