What does "mapping=identity" mean in /etc/exports?

[Greg Scott]

Meanwhile, we went into production with the new NFS server and updated /etc/exports file last weekend.  The app that depends on the NFS server seems to be working just fine.  But in my case, the whole thing is wide open and the app doesn't seem to care a whole lot about mapping user identities.   Since it ain't broke, I don't think I'll try to fix it.  

> I believe this is some arcane invocation of idmapd functionality. Going back to
> SunOS memories, it took the user name (or perhaps number) as trusted and 
>allowed you to access things if your usernum was the same on the client.
> Understand that Solaris replaced SunOS about 20 years ago, and don't put full faith in my memory.
>
>In any case, if you have the same UID on all machines you will probably be fine, 
>but otherwise you will have to build a config file and run idmapd. The documentation 
>sucks, it isn't you, but "man idmapd" will get you started.

- Greg