Every now and again the Ubuntu update servers become a little congested, particularly when there’s a new release of Ubuntu. If you find this happening, switch to an alternative server, preferably located near where your computer is located. there are many servers around the
world, all mirroring the same repositories.
Click System → Administration → Software Sources
Click the Download From drop-down list and then select Other
Click Select best server
You’ll need to reload the package lists from the server when prompted. Don’t worry about the possible security implications of signing up to a server you’ve never heard of. All Ubuntu software packages are digitally signed, so fakery is technically impossible.