Diskless machines normally do the initial root mount read/write
as there is no reason to mount read-only (i.e. for fsck).

*** sys/nfs/nfs_vfsops.c.~24~	Thu Mar  3 19:33:41 1994
--- sys/nfs/nfs_vfsops.c	Sun Mar 13 15:11:46 1994
***************
*** 206,212 ****
  	bzero((caddr_t)mp, sizeof(*mp));
  	mp->mnt_op = &nfs_vfsops;
  	mp->mnt_mounth = NULLVP;
! 	mp->mnt_flag = MNT_RDONLY;
  	mp->mnt_exroot = 0;
  
  	/* Get the root file handle. */
--- 206,212 ----
  	bzero((caddr_t)mp, sizeof(*mp));
  	mp->mnt_op = &nfs_vfsops;
  	mp->mnt_mounth = NULLVP;
! 	mp->mnt_flag = 0;	/* XXX - was MNT_RDONLY; */
  	mp->mnt_exroot = 0;
  
  	/* Get the root file handle. */

This is a handy little fix for debugging.  I needed to know what device
node I was getting to help track down a problem...

*** nfs_vnops.c.orig	Wed Feb 16 05:35:54 1994
--- nfs_vnops.c	Sat Mar 12 12:38:10 1994
***************
*** 1785,1790 ****
--- 1785,1793 ----
  	if (vp->v_type == VFIFO)
  		fifo_printinfo(vp);
  #endif /* FIFO */
+ 	if (vp->v_type == VCHR || vp->v_type == VBLK) {
+ 		printf(", dev %d %d", major(vp->v_rdev), minor(vp->v_rdev));
+ 	}
  	printf("%s\n", (np->n_flag & NLOCKED) ? " (LOCKED)" : "");
  	if (np->n_lockholder == 0)
  		return (0);

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