Confining Strings from $G_2$-holonomy spacetimes

The low energy physics of M theory near certain singularities of $G_2$-holonomy spacetimes can be described by pure N=1 super Yang-Mills theory in four dimensions. In this note we consider the cases when the gauge group is SO(2n), E6, E7 or E8. Confining strings with precisely the expected charges are naturally identified in proposed ``gravity duals'' of these singular M theory spacetimes.