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Checksums

Checksum files are used to verify file integrity, providing a way to check that the local copy of a file is the same as the data-center's copy of the file. Checksum files are computed on a per-folder basis, providing the filename, md5, sha1, and files size for all files in a folder. For folder <folder-name> , the checksum file is called <folder-name>.cksum. Checksum files can be renamed with their folders, if necessary, without compromising the checksum file contents.

The checksum files list one file per line, with the values on each line separated by tabs. Each line provides the md5 hash, the sha1 hash, the file size in bytes, and the filename, in that order. The files are listed in (ascii) sorted order. This format makes it particularly easy to compare two checksum files using standard Unix/Linux tools like grep, awk, and diff.

The DCC provides a program (cksum) for computing and verifying checksum files as part of its CPTAC-DCC Tools package (Windows, Linux, Python versions are available). The checksum files computed by this script are platform independent, so that they can be computed on one platform and verified on another.