Syncing GitHub Apache Hadoop Fork

When you 'Fork' a repository, it doesn't get automatically synced with the original repository.  There a two terms that we need to know.
upstream - The original repository that we have forked from.
downstream - The Forked copy of the original repository.

Following are the steps to Sync the Apache Hadoop Fork
Add the remote upstream URI
git remote add upstream https://github.com/apache/hadoop.git

Fetch changes from the Upstream repository
git fetch upstream

Merge changes (For Hadoop upstream/master did not work for me)
git merge -m "upstream merge" upstream/trunk

Added untracked changes
git add -A

Commit Changes
git commit -m "upstream merge"

Push changes
git push