As a South Indian My name (in public school records) till I was age 21, was <name>. <initial>

I was forced to pick the last name for passport purposes and typically i either have the option of attaching my dad's name or my dad's town name.

My wife, didn't even do that and when she migrated to US, she was <name> LNU (short for Last Name Unknown). While applying for greencard we decided it was too much of a hassle for her and she attached her father's name