error when running apt-get update on ubuntu 14

Solution 1:

Look at the "Secure APT" part of https://cran.r-project.org/bin/linux/ubuntu/README.html:

Adding the key with key ID E084DAB9 fixed the problem for me.

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys E084DAB9

Solution 2:

If you don't need R you can just remove the cran line from /etc/apt/sources.list and you should be good to go.

sudo apt-key del 1445181253 will remove the offending key.