The issue: NFS fails to start in CentOS 7 if it cannot resolve any of a list of hosts.
Well, my manager had to google to find the *truly* obscure solution that uses a deeply oddball syntax.
In /usr/lib/systemd/system/nfs-server.service, you edit the following line so that it looks like this: ExecStartPre=-/usr/sbin/exportfs -r
Notice the *deeply* weird syntax of "=-<cmd>". This apparently tells it that "a nonzero exit code" should be ignored and considered "success".
And, I read in the manpage for systemd.service that if you precede it with an @, it will pass arguments. Why it does not use the used-everywhere-else of *post*fixing those parms, I have no data.
And, speaking specifically about nfs-server.service, I also don't understand why you'd set as an out-of-the-box default that it should fail to come up if it can't resolve any export host, rather than default to coming up.
mark, discovering new reasons to dislike systemd