John Garang, the former rebel leader who spent 21 years fighting the Khartoum government, was sworn in as first vice president yesterday, pledging to promote the unity of the country a day after nearly 1 million people welcomed his return to the capital. Garang took the oath just after President Omar Bashir signed an interim constitution that promises broader freedoms for Sudanese and brought an end to the state of emergency that has been in place off and on since 1989.