Manual page and help for the ddrescue linux command. GNU ddrescue is a data recovery tool that copies data from one file or block device to another, first attempting to save the error-free portion of the data. Always use a map file unless you know you don’t need it. Without a map file, ddrescue cannot continue the data backup, it can only restart the process. NOTE: In ddrescue versions prior to 1.20, the map file was called a “logfile”. The format is the same, only the name has changed. If you are restarting the system, check the device names before restarting ddrescue. Do not use the program with the "-F" or "-G" options until you have read the manual page of the program.