Fix system with sources.list containing both Precise and Qantal releases

Fix system with sources.list containing both Precise and Qantal releases

I installed Precise 64 bit Server (12.04 LTS) successfully at first.
However, after installing various packages to aimed at supporting
node/oracle development, my system appeared to have become Quantal:
guob@sedona:/etc/apt/apt.conf.d$ cat /etc/lsb-release DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=12.10 DISTRIB_CODENAME=quantal DISTRIB_DESCRIPTION="Ubuntu
12.10"
For fear of being unable to access the server, I have not cycled the
server so far.
The sources.list shows mixed sources for both precise and quantal:
deb http://us.archive.ubuntu.com/ubuntu/ precise main universe restricted
multiverse deb http://archive.ubuntu.com/ubuntu quantal main universe
restricted multiverse
As a newbie, I have been puzzled how this could have happened. More
importantly, I urgently needed advice on how to revert system back to
12.04 LTS.
Thanks in advance!
Bo