SystemRescueCd is a free system rescue disk, which can be booted from either a CD-ROM or USB drive, or installed onto a hard drive. Its primary use is in administrating or repairing a computer system that can no longer be booted, usually as the result of a crash. Through the rescue disk, users can restore, reformat, debug, create or otherwise modify the partitions of a hard disk, or backup important data on a computer system that can no longer be booted. Moreover, it includes various tools, such as PhotoRec and ddrescue, which can help to recover lost data from physically damaged drives.