i have reinstalled ubuntu 13.10 saucy. actually the problem is that when i try to download from ubuntu software centre , it says the software is availble from the universe source , and showing an option of 'use this source' but when i click it nothing happen in progress bar. it is not with all softtwares but most of them. actually when earlier i installed i was facuing the same problem i found something(command) on internet and ran it on terminal. and then it works. but now i dont have that command . i also have enabed universe source in setting software and updates tab. bbut still faacing this. can anybody please provide me those commands to add repositry for saucy. i can remeber that it was three step command. having 'sudo' in first command. update in second or third. please i dont understand all thease things please help me plz. because without it my ubuntu is looking useless all the useful softwares need that universe repositry. thanks in advance.