The son of Umar Ibn Al Khattab. Do Shias accept his narrations?
Abdullah ibn umar (the son of second Caliph), did not swear allegiance to Imam Ali (a.s.). Although he was not from Imam Ali’s enemies. He did not support of Imam’s opponents, and so on. According to some narrations, at the end times of his life, Abdullah regretted that he didn’t support Imam Ali (a.s.) and did not war beside him.
He can be deemed as a non-politic individual who often was following of individual worship. And it was due to his incomplete ability in politics that he was far of it. (He didn’t see sufficient ability and cleverness in himself to participate in politics.)
Source and detailed answer in Persian (Farsi): www.islamquest.net