/usr/share/eccodes/definitions/metar/clouds.table 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 4 5 | SKC|0|Sky clear|
FEW|1|Few|
SCT|2|Scattered|
BKN|3|Broken|
OVC|4|Overcast|
|