I know this subject has come up quite a few times so far (with different distro's of texlive). See for instance:
Missing tlmgr texlive 2012
tlmgr: TeX Live 2011 is frozen forever
Texlive installation is missing tlmgr, how to fix?
None of them provided a solution that worked for me. The last link implies that the Ubuntu developers decided not to include tlmgr in the texlive distribution.
I installed texlive afresh via the following instructions: http://askubuntu.com/questions/160676/problems-installing-tex-live-2012-on-12-04
My texlive distro apparently lives here:
$ whereis texlive: /usr/share/texlive
Any clue where to find tlmgr or how to activate it without reinstalling the texlive distribution all over again?