If the text is in first person, then in which person should the summary be written?

Even when a text is written in the first person perspective, your summary should be written in the third person perspective unless otherwise specified.

A summary should relate your understanding of the themes and events which occurred in the text. Try to imagine you are writing to someone who has not read the text before, and you'd like to give them a description of what the story was about. Think "short and sweet!" What are the most important points of the text?

If your teacher has specified that the summary ought to be written in first person, or from the perspective of the narrator of the text, then it is okay to write in first person. Try to put yourself in the narrator's shoes, but still relate the most important points of the text.