How do I remove a PPA added via command-line?

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http://askubuntu.com – I added a PPA for updating my kernel for ubuntu-12.04. Later, I found that the kernel doesnot exist on the link within PPA. I used this command. sudo add-apt-repository ppa:kernel-ppa/ppa Now if I try sudo apt-get update, I get an error 404, because http://ppa.launchpad.net/kernel-ppa/ppa/ubuntu/dists/precise/main/source..., does not exist. Trouble is I am unable to do an update. Even not able to do sudo ppa-purge ppa:kernel-ppa/ppa Suggest a solution. (HowTos)