What is the default password of user and guest in Ubuntu 12.04

Greetings from the Dakota's! I came looking after an apt-get update messed up my new (very old stock!) PCduino. She worked great with the original Lubuntu on it, I was doing all my old favorite Linux functions and having a ball. Then I rebooted, and BANG! I couldn't do squat. I could not log in as ubuntu as it wanted me to, it would not take the ubuntu password, so I logged in as guest and it wouldn't let me sudo or su. So I began messing around and looking all over the web for a good answer, never really found one, but then it came to me, try ubuntu password for sudo on the guest account, didn't work very well, so I tried su with that password and I was IN! I quickly made myself an account with my name, then added myself to the SUDO list and I am again off and running with my new little toy. Sure wish the EBAY seller would have told me he was selling me a gizmo that was 5 years out of date and 3 generations of processor behind the current type, but I guess for ten bucks you can't expect the Cadillac, you need to be happy with the Chevy of the line,.

The Ubuntu 14 image I have for VMware has passwords defaulted to "password". I attempted to use sudo. It asked for "password for user". I typed "password" (without the quotes) and sudo completed the operation.

I had the same experience. In my case I tried and the default administrator's password was "ubuntu".

There is no default user (and therefore no default password) on Ubuntu. The guest user cannot perform any administration tasks at all.

As you completed the installation you must have chosen a username (and a password) during that process. Use that username and password to access your machine.

If you cannot remember the password see this answer to How do I reset a lost password

If the VM is brand new (and if the above process gives you troubles) it might be easier just to reinstall (and take note of some crucial settings).

Reboot your system and select Advanced options from grub. Then select Ubuntu (recovery mode) and create new user or change password for existing:

Creating new user:

adduser <username>

(replace <username> with the accountname you want to use)

Now just follow the steps and fill the information:

Adding user "new_user"
Adding new group "new_user" (1004).
Adding new user "new_user" (1004) with group "new_user.
Creating home directory "/home/new_user".
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
Changing the user information for new_user
Enter the new value, or press ENTER for the default
Full Name []:
Room Number []:
Work Phone []:
Home Phone []:
Other []:
Is this information correct? [y/N] y

By default the password for any guest user is disabled. So you don't have to enter any password for guest.

Also, by default, Ubuntu doesn't have any user named "user", only if you created one with this name and only you should know the password for this account in this case. If you don't remember it, see: How do I reset a lost password (using recovery mode requires me to type the password)?