You probably have a "hier" man page on your system. https://man7.org/linux/man-pages/man7/hier.7.html https://man7.org/linux/man-pages/man7/hier.7.html Also sy

You probably have a "hier" man page on your system. https://man7.org/linux/man-pages/man7/hier.7.html https://man7.org/linux/man-pages/man7/hier.7.html Also systemd has a "file-hierarchy" man page for its understanding of the hierarchy, which includes e.g. its use of /run and which directory can be read-only - https://man7.org/linux/man-pages/man7/file-hierarchy.7.html https://man7.org/linux/man-pages/man7/file-hierarchy.7.html