/usr/share/eccodes/definitions/mars/grib.mdfa.fc.def is in libeccodes-data 2.6.0-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | # assert(localDefinitionNumber == 1);
alias mars.step = stepRange;
unalias mars.time;
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