Digging up the Past Achievement in Halo: The Master Chief Collection

Towards the start of the first mission, this achievement can be obtained fairly early on before any big firefights or events even occur. After gaining control of the Master Chief, simply walk forward through the corridor ahead.

Instead of passing into the next room, turn to the left and descend the staircase. Down here, you will spot a terminal of the other side of the room, so approach the console and activate it to read the Master Chief’s records, thus unlocking the achievement. Take note that this terminal does not necessarily count towards the "Terminus" achievement.