I have an Ubuntu 11.10 VPS running inside OPenVZ with a hosting company. I'm trying to get it to mount a remote NFS server using NFS4, but can only get it working using version 3. I've been Googling around this quite a lot and occasionally I'll read something along of the lines of "NFS4 clients can't work inside OpenVZ containers". I can't find an up-to-date concrete answer to this so I'll ask here:

Is this true, and if so, great - then I can stop trying to get this to work! But if it IS possible, why's it not working?? Here's what I've done --

  • nfs-common installed on client, nfs-kernel-server installed on server
  • saw some instructions to install nfs-utils on client, but apt-get can't find the package
  • mount from client to server works successfully with NFS vers 3
  • server seems to be working fine; can mount successfully using NFSv4 from an Ubuntu VM running on my desktop
  • BUT on the successful client machine nfs AND nfs4 is listed in /proc/filesystems, on the problematic one it's only nfs
  • I logged a ticket and the relevant module's now been installed on the VPS node, according to the engineer responsible. He's replied that it should now be working but I think he may have just re-enabled the "standard" NFS module (see above re: cat /proc/filesystems | grep nfs)

    $ sudo mount -v -t nfs4 [SERVER_IP]:/ /NFS-ARCHIVE/ mount.nfs4: pinging: prog 100003 vers 4 prot tcp port 2049 mount.nfs4: No such device

    $ sudo mount.nfs [SERVER_IP]:/ /NFS-ARCHIVE/ -w -n -o nfs4 mount.nfs: Unsupported nfs mount option: nfs4

  • I've read that I might need to manually load the module by running modprobe nfs before mounting, but I don't think I can do that on a VPS. sudo modprobe -l on the client returns nothing

Any help much appreciated, especially if you can categorically answer the first question - at least if I know it's impossible I can then move onto setting everything up using vers 3!

  • In case anyone from the future finds this question: I continued reading up on the issue but couldn't get a solid answer stating whether NFS4 was supported in OpenVZ based VMs. But I did come across this great post, which explained some VPS basics for me, the most useful of which was that Xen-based VMs, while maybe not quite as well-performing as OpenVZ-based ones, should allow you to load kernel modules at will. I switched over to a Xen container and had no problem getting NFS4 (and bonus: ufw) working easily – Mark G Mar 9 '12 at 19:33

Later versions of OpenVZ do support NFS4 in container. We are using the latest CentOS 6.2 together with the latest stable OpenVZ release 2.6.32-042stab053.5 and NFS4 do work well for us.


While NFS 4 clients do work in an OpenVZ VPS (tested with Proxmox 2.1) if the feature nfs:on is enabled and the nfs module is loaded on the host (i.e. container 0), the name -> UID lookups are always done using the rpc.idmapd running on the host. This means that you need to have the same users in your host /etc/passwd as in your VPS.

Furthermore, the default mount option sec=sys permissions don't work right if the UIDs/GIDs numbers don't match between your VPS, host and server! One would expect that with nfs3 (since it sends UID/GID numbers over the wire), but with nfs4 the username/groupnames are sent. See http://thread.gmane.org/gmane.linux.nfsv4/7103/focus=7105 (and answer to RHEL - NFS4: Mounted/Exported as rw, user write permission denied) for more details.

The upshot is you can mount nfs4 inside a VPS with sec=sys provided

  1. You have a new enough openVZ kernel.

  2. You have enough control over the host and VPS setup to

    • enable the nfs:on option for the nfs4 client VPS
    • load the nfs module on the host
    • run the rpc.idmapd daemon on the host
    • control the /etc/passwd entries on the host
  3. You can live with the limitations implied by having to share VPS/host usernames.

It may be possible to set up something more flexible using kerberos/ldap or perhaps even if there is a way to control the idmapd domain used for the mount, but I have no experience with those options.


The VPS itself has to have the feature nfs:on enabled. Ask your hosting company to enable that.

You can find more information on the Wiki: http://wiki.openvz.org/NFS

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.