Cannot obtain lock: E: Could not get lock /var/lib/dpkg/lock-frontend. It is held by process 2795 (apt) W: Be aware that removing the lock file is not a solution and may break your system. E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it?
*** This bug has been marked as a duplicate of bug 501468 ***