Is Daru a reliable narrator?

This is an interesting question. Daru is definitely a sympathetic narrator. Daru lives alone in his schoolhouse on the dust swept Algerian mountain but feels himself privileged to do so,

"In contrast with such poverty, he who lived almost like a monk in his remote schoolhouse, nonetheless satisfied with the little he had and with the rough life, and had felt like a lord with his whitewashed walls, his narrow couch, his unpainted shelves, his well, and his weekly provision of water and food."

Daru wants to do the right thing but isn't completely sure what the right thing to do is. Daru is a pacifist in an atmosphere charged with the potential for violence. It is Daru's conduct amidst the coming chaos that I think makes him a reliable narrator. Daru seems incapable of lying. He tells Balducci that he would never dispute what happened and Balducci knows Daru's word is his bond. Daru risking his own fate to the forces of his reality: he offers the Arab freedom to choose Arab or French law. This is exactly what makes him a reliable narrator: Daru has nothing to gain by leaving the Arab at the top of the hill. In the end all Daru is left with is a threat scrawled on a chalkboard and existential angst.