Index: sys/boot/forth/loader.conf.5
===================================================================
--- sys/boot/forth/loader.conf.5
+++ sys/boot/forth/loader.conf.5
@@ -112,6 +112,23 @@
 that contains a kernel.
 .It Ar kernel_options
 Flags to be passed to the kernel.
+.It Ar vfs.root.mountfrom
+Specify root partition in a way the kernel understands.
+For example:
+.Pp
+.Dl vfs.root.mountfrom="ufs:da0s1a"
+.Pp
+Normally, value of this tunable is automatically derived and set by the
+.Xr loader 8
+after reading and parsing
+.Pa /etc/fstab .
+This parameter is provided for the cases when
+.Pa /etc/fstab
+cannot be accessed by the
+.Xr loader 8
+or is not available at the time when
+.Xr loader 8
+runs (e.g. diskless booting from NFS).
 .It Ar password
 Protect boot menu with a password without interrupting
 .Ic autoboot