nfsd.8: Add a short paragraph w.r.t. NFSv3 vs NFSv4 setup

The nfsd can be configured to support NFSv3, NFSv4 or both
of them.

This patch adds a short paragraph to nfsd.8 to explain this.

This is a content change.

Reviewed by:	kib, zaiee (manpages)
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D54279

1 files changed, 60 insertions, 2 deletions

diff --git a/usr.sbin/nfsd/nfsd.8 b/usr.sbin/nfsd/nfsd.8
index 2e5724dbce33..79085d33230c 100644
--- a/usr.sbin/nfsd/nfsd.8
+++ b/usr.sbin/nfsd/nfsd.8
@@ -25,7 +25,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd May 30, 2025
+.Dd December 23, 2025
 .Dt NFSD 8
 .Os
 .Sh NAME
@@ -46,7 +46,7 @@ NFS server
 .Sh DESCRIPTION
 The
 .Nm
-utility runs on a server machine to service NFS requests from client machines.
+utility runs on a server machine to service NFSv4 and/or NFSv3 requests from client machines.
 At least one
 .Nm
 must be running for a machine to operate as a server.
@@ -54,6 +54,62 @@ must be running for a machine to operate as a server.
 Unless otherwise specified, eight servers per CPU for UDP transport are
 started.
 .Pp
+The
+.Nm
+server may be configured to serve NFSv3, NFSv4 or both of them.
+When
+.Bd
+nfs_server_enable="YES"
+.Ed
+is set in
+.Xr rc.conf 5 ,
+.Nm
+is configured for NFSv3 only, by default.
+To configure the
+.Nm
+to serve NFSv4, you must also:
+.sp
+.Bl -bullet -compact
+.It
+Add a
+.Dq V4:
+line to
+.Xr exports 5 .
+(This is needed as well as either the ZFS sharenfs property
+or an exports line for each exported file system.)
+.It
+Either choose to do uids in
+.Dq strings ,
+which is probably
+the easiest unless you are doing
+.Xr kerberos 7
+mounts or
+run
+.Xr nfsuserd 8
+.Pq choose one, not both of these .
+Setting the sysctls MIBs
+.Va vfs.nfs.enable_uidtostring
+and
+.Va vfs.nfsd.enable_stringtouid
+to one and not running the nfsuserd chooses uids in
+.Dq strings .
+.It
+Set
+.Bd
+nfsv4_server_enable="YES"
+.Ed
+in
+.Xr rc.conf 5
+or set
+.Bd
+nfsv4_server_only="YES"
+.Ed
+in
+.Xr rc.conf 5
+if you do not want NFSv3 to be served.
+.El
+.sp
+.Pp
 When
 .Nm
 is run in an appropriately configured vnet jail, the server is restricted
@@ -336,7 +392,9 @@ just do a
 .Xr pnfs 4 ,
 .Xr pnfsserver 4 ,
 .Xr exports 5 ,
+.Xr rc.conf 5 ,
 .Xr stablerestart 5 ,
+.Xr kerberos 7 ,
 .Xr gssd 8 ,
 .Xr ipfw 8 ,
 .Xr jail 8 ,