/var/lib/pcp/config/pmchart/Filesystem is in pcp-gui 3.10.8build1.
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 | #kmchart
version 1
chart title "File System Fullness % [%h]" style plot
plot legend "%i" metric filesys.full not-matching "/dev/shm|/dev$"
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