What is a BAK2 File Type?
All BAK2 files have a compound file extension. The file is added to a file for which it stores information, such as a PLAYER or SHIPWORLD file. If the file stores backup information for a SHIPWORLD file, for example, the file name will be ab 07704dbcb4162646d4d93bbeef34df.shipworld.bak2.
You can delete the file from the file name and open it as a SHIPWORLD file in Starbound. It is important, however, that you do not change the string before the extensions.
The BAK2 files are located in the player " directory in the Starbound directory. For example if you purchased Starbound through Steam, the BAK2 files are stored in the following location in Windows:
Program Records / Steam / SteamApps / Common / Starbound / Player.
It also uses .BAK1 and .BAK3 files.