Re: FreeBSD nfsroot - will it work with NFSv4.2?

On Fri, 20 Feb 2026 at 00:01, Rick Macklem <[email protected]> wrote:
>
> On Thu, Feb 19, 2026 at 2:40 PM Dan Shelton <[email protected]> wrote:
> >
> > On Thu, 19 Feb 2026 at 23:30, Rick Macklem <[email protected]> wrote:
> > >
> > > On Thu, Feb 19, 2026 at 2:23 PM Dan Shelton <[email protected]> wrote:
> > > >
> > > > Hello,
> > > >
> > > > Will a FreeBSD 15.0 diskless setup with nfsroot work with NFSv4.2?
> > > Nope. On FreeBSD a diskless NFS root fs must be NFSv3.
> >
> > Which is a bit of a problem since our IT guidelines prohibit the use of NFSv3.
> > Also, we assume that NFSv4.2 will perform much better, and we need ACL support.
> >
> > > (There are various bootstrap issues, such as a standalone NFS client
> > > that does not do NFSv4.
> >
> > Do you have a full list?
> Well, fixing the uid/gid mapping issue is the main one.
>
> To be honest (I've wondered why for many years) FreeBSD has two
> different ways that an NFS root fs can be booted.
> - One of them (which seems to be favored by the x86 crowd) uses
>   the afor mentioned NFSv3 standalone client.
> - The other doesn't use the NFSv3 standalone client and uses bootp.
>   (It seems to be favored by the non-x86 folk, like arm.)
>
> If only using the second one would be acceptable for NFSv4 root
> file systems, then it probably isn't that hard to do (hardwire a few
> mappings, so it works until nfsuserd is running) and fix up any
> bootstrap issues (FreeBSD servers generate the same file handles for NFSv3
> and NFSv4, but the client would need to handle any NFSv4 file handle
> of up to 128bytes.)
>
> I don't currently have a diskless setup to play with, but I will
> put it onto my to-do list. (The list never gets empty and often
> gets priority items, so I cannot say when I'll get around to it.)
>
> Of course if someone like yourself was to do it and come up
> with a patch, that would speed up the process.
>
> >
> > > There is also the handling of
> > > uid/gid<-->user/group name
> > > mappings by nfsuserd, which cannot be running until it is booted.
> > > Yes, there are ways to handle the mappings:
> > > - Do it like Linux and insist that it be uid/gid numbers in the strings.
> > > or
> > > - Hardwire enough mappings in the kernel to get the system going so
> > >   that nfsuserd can run.
> >
> > Can such a list be built in, or passed as a boot argument string?
> >
> > >
> > > Since there has not been any demand for NFSv4 diskless root file
> > > systems, it has not been done.
> >
> > We have demand, if we get a contract for that cluster setup... which
> > requires that this actually works in a demonstrator.
> >
> > I recall that there was this topic when Opensolaris.org was active,
> > but I never followed the SUN bugster RFE to implement that feature.
> > Everyone was just bloody crazy that ZFS will take over the world, so
> > cluster setups with nfsroot were treated like the orphaned stepchild
> > which also has rabies and scabies.
> I do know some folk use diskless NFS root file systems, but I have no
> idea how many there are? You are about the 2nd person to ask about
> NFSv4 root file systems.

NFSv4.2 root filesystem

Dan
-- 
Dan Shelton - Cluster Specialist Win/Lin/Bsd