config/network-filesystems.md: document NFSv4-only server setup

Author: slymattz

src/config/network-filesystems.md

@@ -8,8 +8,9 @@ To mount an NFS share, start by installing the `nfs-utils` and `sv-netmount`
 packages.
 
 Before mounting an NFS share, [enable](./services/index.md#enabling-services)
-the `statd`, `rpcbind`, and `netmount` services. If the server supports `nfs4`,
-the `statd` service isn't necessary.
+the `statd`, `rpcbind`, and `netmount` services. Both `statd` and `rpcbind`
+services are only needed for NFSv3, so if you mount shares on your clients like
+that, keep them. For NFSv4 shares, `netmount` is enough.
 
 To mount an NFS share:
 
@@ -69,3 +70,39 @@ server status:
 
 You can use [nfs.conf(5)](https://man.voidlinux.org/nfs.conf.5) to configure
 your server.
+
+### Setting up a server (NFSv4-only, Kerberos disabled)
+
+If you don't plan on using NFSv3 even as a fallback option, you can set up an
+NFSv4-only server. This will let you eliminate the need for
+[enabling](./services/index.md#enabling-services) `statd` and `rpcbind`
+services, be it on server or client side.
+
+First, install `nfs-utils` and follow the instructions about `/etc/exports`
+listed above.
+
+Then, edit `/etc/nfs.conf` and disable version 3, as in:
+
+```
+[nfsd]
+vers3=n
+vers4=y
+vers4.1=y
+vers4.2=y
+```
+
+To verify which versions are enabled or disabled, run:
+
+```
+# cat /proc/fs/nfsd/versions
+```
+
+As the last step, set `NFSV4_ONLY` to a non-empty value in
+`/etc/sv/nfs-server/conf`
+
+```
+NFSV4_ONLY=true
+```
+
+Now you can [enable](./services/index.md#enabling-services) `nfs-server`
+service.