After downloading the latest stable version of Crate from http://download.cratedb.org/ the package needs to be unpacked:
sh$ tar zxf crate-*.tar.gz
Now Cate can be started in the foreground like this:
sh$ ./bin/crate -f
In order to start in the background omit the -f option. If started in the foreground you can use Control-C to stop the process again.
Note
Crate needs a working Java >= 1.7 installation in order to run.
See also