Issue installing elasticsearch 1.0.6

$ echo "deb stable main" | sudo tee -a /etc/apt/sources.list.d/elasticsearch-1.x.list
deb stable main

$ sudo apt-get update && sudo apt-get install elasticsearch
W: Failed to fetch 404 Not Found [IP: 80]

Looks like you are using the wrong repository URL. Here's the official doc for where deb packages are hosted:

Maybe the following thread helps you as well: