nfs: add rd_NFS_DOMAIN parameter to set the NFSv4 domain name

https://bugzilla.redhat.com/show_bug.cgi?id=537969

dracut.8

@@ -231,6 +231,9 @@ options can be specified.
 \fBDeprecated!\fR kernel Documentation/filesystems/nfsroot.txt defines 
 this method.  
 This is supported by dracut but not recommended.
+.TP
+.B rd_NFS_DOMAIN=<NFSv4 domain name>
+Set the NFSv4 domain name. Will overwrite the settings in /etc/idmap.conf.
 
 .SH iSCSI
 .TP

modules.d/95nfs/nfsroot

@@ -133,7 +133,11 @@ if [ "$nfs" = "nfs4" ]; then
 
     # XXX really needed? Do we need non-root users before we start it in
     # XXX the real root image?
-    [ -z "$(pidof rpc.idmapd)" ] && rpc.idmapd
+    if nfsdomain=$(getarg rd_NFS_DOMAIN); then
+        [ -z "$(pidof rpc.idmapd)" ] && rpc.idmapd -d $nfsdomain
+    else
+        [ -z "$(pidof rpc.idmapd)" ] && rpc.idmapd
+    fi
 
     # XXX Should we loop here?
     mount -t nfs4 -o$options${nfslock+,$nfslock} \