I just can't bend my brain to understand how the -f and -u flags are supposed work
together...

-f says to always remove existing target file in favor of source file
-u says only copy if source is newer than an existing target

anyone that can enlighten me?

After playing with cp for a while it seems that (at least on Debian x86 Linux) -u
beats -f, and if target file, newer than source file, exists, no copy is performed, no
matter in what order the flags are given.

For a freshly created disk (from factory or after applying the builder .upgrade)
which the FAQ procedure uses, neither -f nor -u should be necessary, as there are
no existing fid files in the target that we need to clobber or preserve. If you're
playing around having mounted a partition under /drive0 on the source drive you
probably also know enough to append 'x' on your own...

The /drive0/ instead of /drive0 is a good precaution, though if /drive0 is missing you
have something seriously wrong and will probably need to reapply a .upgrade file
anyway...

Tony, generally flags in Unix can be given separately, like '-f -a -q', or in one go
(some exceptions exist) like '-faq'

Considering the fact that the FAQ presumes a fresh drive, I'd say

cp -av /drive1/fids /drive0/ (Enter)

for the FAQ, with a small note that if you already have partially copied the fids,
change '-av' to '-avuf'. Or just point to this thread

Edit:

Bah, also given the fact that the FAQ presumes a fresh target - adding the -u
and -f flags will do no harm, and might be useful on other occasions - I'll change my vote to

cp -avuf /drive1/fids /drive0/ (Enter)

/Michael