How long does Okonkwo have to leave Umuofia?

During Ezeudu's funeral, Okonkwo accidentally kills a clansman (Ezeudu's son) when his gun explodes.

Whenever a man kills a clansman, it is an affront to the Earth goddess, and the murderer must be exiled from the village, according to the tribe's traditions, with the murderer's possessions destroyed. However, since it was an accident (the female version of the crime), he is only exiled for seven years as opposed to life.