@cJ It's present in SUSv2 (only available as PDF) hence why I said historical standard, although was already marked as obsolescent by then.

> You say nothing else needs to be remembered, but at least --one-file-system is a regular in my tar and rsync invocations.

Well never used that one, although I guess for the special case of backups I could but for me those go in scripts, including for restoring. And checking manpages while writing scripts is typically the way I go so mnemonics aren't needed.
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