One or more techniques and/or computing devices are provided for restarting a dump backup. For example, a phase offset table is used to track a directory transfer phase offset and a file transfer phase offset of phases of a dump backup. An offset map is used to map inodes, of data being backed up, to offsets within a backup image within which the data is being backed up. The phase offset table and/or the offset map are evaluated using a bytes written value to identify a phase during which the dump backup aborted and to identify a restart point. Accordingly, the dump backup is restarted at the restart point. In this way, the dump backup may be restarted during any phase and/or at any point using the bytes written value, the phase offset table, and the offset map without the need for additional information such as a file history.