There is a menu shortcut to run all cells under Cell > "Run All". This isn't bound to a keyboard shortcut by default- you'll have to define your own custom binding from within the notebook, as described here.
For example, to add a keyboard binding that lets you run all the cells in a notebook, you can insert this in a cell:
%%javascript
Jupyter.keyboard_manager.command_shortcuts.add_shortcut('r', {
help : 'run all cells',
help_index : 'zz',
handler : function (event) {
IPython.notebook.execute_all_cells();
return false;
}}
);
If you run this code from within iPython notebook, you should find that you now have a keyboard binding to run all cells (in this case, press ctrl-M followed by r)