49-52 should be deleted. It's fine when ${TARGET} do not exist, we can generate its contents.

Because this is a template, it do not really need the header anymore, because we prepend it anyway. This should be replaced with:

sed '1{/^FreeBSD.*/{d;};};' "${COMPAT_MOTD}" > "${TEMPLATE}"

TEMPLATE permission should be set here (or after line 34).

41-42: ln -sF "${TARGET}" "${COMPAT_MOTD}" would take care of the pre-existing file.

45-47: If after the above dance the template still do not exist as a file, we should bail out (return) or just ignore.

Note that since we now store template separately, this edit should only happen once. In other words, replace this with cat "${TEMPLATE}" >> ${T}

This line should be deleted.

Hm, what do you think about testing ${TARGET}/.. (i.e., "/var/run") for writability instead?

if [ ! -w /var/run ] || [ -f "${TARGET}" -a ! -w "${TARGET}" ]; then
    ...

OTOH, the test is inherited from the pretty ancient script; maybe we can assume we have a writable /var/run now. I am ok to delete it if you prefer.

Thanks, will fix.

Will fix, thanks.

-F or -f? Do we have any reason to believe /etc/motd is a directory? And if it is, that it is empty?

Yes, -f takes care of the expected preexisting file. I guess ln -sf unconditionally unlinks and recreates the symlink inode every time, but we are still conditional on [ ! -f $TEMPLATE ], so probably the IO isn't a concern.

Will plan to change to -f unless you feel strongly about -F.

Ok

Will fix.

Will fix, thanks.