One option is to view (maybe edit) the /etc/sudoers file via single user mode, (if visudo command is available just run that; else, recall that when using vi or vim, :w! will save a write protected file.. But actually EDITING the sudoers file should be a last resort in this case - you can make things worse by 'visudo' command is like crontab -e, in that is checks syntax before committing changes, which is why you should really use it if its available) .  

I think all you *really* need to do is place your desired user 's account as a member of the correct group (which is why we are viewing the sudoers file, so see which group is given "ALL").  The group is most likely "admin" (confirmed in the link below; in which case in single-user mode, edit /etc/group, and place your self in that group, following other group member syntax examples already in the file for reference). 

More info sudoers in Ubuntu: https://help.ubuntu.com/community/Sudoers

Ben



On Fri, Dec 30, 2011 at 3:05 PM, Kevin Fries <kevin@fries-biro.com> wrote:

Resetting the root password will get you nowhere.  Those directions are old and should not be used.

If you can get yourself root access, simply add your everyday account to the admin group.

I have not tried to single user access a machine with grub2, so I am less help there, hopefully someone else can help with that.

Kevin

On Dec 30, 2011 2:59 PM, "Ariel Gold" <arielqgold@gmail.com> wrote:
sorry, didn't read your whole post. but i recently used these instructions to reset a root password. http://www.howtoforge.com/how-to-reset-a-forgotten-root-password-with-knoppix  I booted from an Ubuntu cd instead of a Knoppix one...  (make sure you read the second page of that article, that's where the meat of it is)



On Fri, Dec 30, 2011 at 2:41 PM, david lopez <lopezdavid123@gmail.com> wrote:
Need help! (ubuntu 11.10)

Somehow managed to do a stupid thing -- that is, from the

   User_name in menu bar-->User Accounts
  
I managed to make all my login accounts 'standard' (normally at least one
login account is 'admin'). When I a try a 'sudo cmd', it says that the
user "is not in the sudoers file". When I try to go back to the User Accounts
gui and use the unlock icon and enter the correct password, the error
is "An application is attempting to preform an action that requires privileges.
Authentication as super user is required to perform this action".

Some linux web pages have recourse assuming the super user account password
has been lost and you may fix it by booting up the session with 'single'
user mode and changing the password via a root command 'passwd'. Since I
can still login into the account which should have super user privileges,
it is not clear that single user mode to change the password will correct
my lack of admin privileges problem.

BTW, I have not found single user mode recipe for ubuntu 11.10 on the web
that works so I don't know if re-setting the password will fix my lack of
admin privileges.

Two issues:
 1) How do I remedy my issue in restoring my "admin" privileges
 2) The gui should always make sure that at least one login account has
    'admin' privileges.
   
If fixing issue 1) involves the 'single' user mode, where is a good web
recipe for ubuntu 11.10.

David


--
David Lopez
Software Engineer

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Ben

python -c "exec(\"import math\\nprint ''.join(map(lambda x: chr(x), ( (ord('a')-(3*5)), int(math.sqrt(math.pi*76)*5+2), int(math.ceil(math.e)*28), int(math.floor(math.e)*35), long(abs(4%3*35+3)*2))))\")"