Several networked filesystems (i.e. afs) have similar concepts. This just
moves it into the vfs layer so that it can be used on all of them and even
local filesystems.
The best example of how this can be useful is to allow a heterogeneous
environment which uses a common filesystem. For example, both x86_64 and
power systems could mount a root nfs share and execute with a common set of
configurations and data, but the binary directories (bin and lib) could
point to architecture specific directories.
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