I am new to ubuntu. I have just switched from win7 to ubuntu 12.04. After installing ubuntu I put to install all my required packages from software center but one weired thing I noticed is that few packages were not got installed(not sure if only few or many but I noticed few like java, synaptic package manager) from software centers. I had to run apt-get command from terminal to install these softwares. I did not see any error thrown by software centers for these packages that means these were downloaded by software center properly. I am not sure if these packages were downloaded then where did the gone and why did they were not got installed.