My OS is Ubuntu 12.10, and my account is called acgtyrant, and its UID is 1000. For the need of researching, I changed my UID from 1000 to 1010 in /etc/passwd, and then I found my files' master changed to a number:1000, which prove my suppose. But when I try to change my UID back, I found I can't edit the passwd file any more! Because when I try to run sudo vim /etc/passwd, the Bash told me sudo: unknown uid 1000: who are you?.
So how to solve it? Acctually I am a chinese student, so forgive my poor English please.