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This page describes how to use NFS client inside a container.

Yellowpin.svg Note: see NFS server inside container for info about nfsd.

Mounting filesystems from the hardware node can be performed more elegantly using Bind mounts.



You will need the following software:

  1. vzctl version 3.0.13 or higher (do vzctl --version)
  2. kernel version 2.6.18-028test006 or higher (2.6.18-028stab* will do), or any recent RHEL5-based or 2.6.20-based kernel.

Note: In all the kernels earlier than 028stab038, kernel NFS support can be given to a container by setting:

     sunrpc.ve_allow_rpc = 1
     fs.nfs.ve_allow_nfs = 1
     kernel.ve_allow_kthreads = 1

This can be done by adding the above lines into /etc/sysctl.conf on the hardware node, and then running sysctl -p.

Prepare the HN[edit]

For NFS mounts to work in the containers with the RHEL5-based kernels you must enable kernel threads in the container by setting kernel.ve_allow_kthreads=1 in /etc/sysctl.conf.

RHEL7-based kernels support three different NFS protocol versions:

NFS version 2 (NFSv2) is older and is widely supported. NFS version 3 (NFSv3) has more features, including 64bit file handles, Safe Async writes and more robust error handling. NFS version 4 (NFSv4) works through firewalls and on the Internet, no longer requires portmapper, supports ACLs, and utilizes stateful operations. Red Hat Enterprise Linux supports NFSv2, NFSv3, and NFSv4 clients, and when mounting a file system via NFS, Red Hat Enterprise Linux uses NFSv3 by default, if the server supports it.

Accordingly, there are three kernel modules: nfs (for NFSv2), nfsv3, and nfsv4. As NFS server inside container currently only supports NFSv3, it's very likely that you'll need to load nfsv3 module for clients.

# modprobe nfs

You will probably want the nfs module to load automatically on reboots. One way to do this is to put the modprobe command in your /etc/rc.d/rc.local file:

 modprobe nfs

Alternatively, you can add a new line with nfs to your /etc/modules or /etc/modules.conf file.

Prepare the container[edit]

To allow a container to use NFS filesystem, you will need to start it with "nfs" feature enabled. If the container is running while you set the --features nfs:on, you will need to reboot it.

# vzctl set 101 --features "nfs:on" --save
# vzctl start 101

After this you may see nfs in /proc/filesystems

# vzctl exec 101 cat /proc/filesystems
nodev   rpc_pipefs
nodev   proc
nodev   nfs
nodev   sysfs
nodev   tmpfs
nodev   devpts

Mounting NFS[edit]

Make sure that packages nfs-utils and nfs-utils-lib or similar are installed in a container. Also make sure that the portmap (or rpcbind) service is started, otherwise the mount with default options will fail and require the -nolock option. See the known issues for more information.

Assuming that you already have NFS server set up at, mounting will be simple

# vzctl enter 100
# mkdir /nfs
# mount -t nfs /nfs
# cat /proc/mounts 
simfs / simfs rw 0 0
proc /proc proc rw 0 0
sysfs /sys sysfs rw 0 0
devpts /dev/pts devpts rw 0 0
nfs /nfs nfs rw,vers=3,rsize=32768,wsize=32768,hard,proto=tcp,timeo=600,retrans=2,sec=sys,addr= 0 0

For more details on how to setup NFS mount, see NFS-client HOWTO

Known issues[edit]

  • There are quite a few parameters in NFS, so sometimes it doesn't work due to misconfiguration. We've created a separate page describing such situations: NFS doesn't work.
  • Package nfs-common can not be installed. Make sure you start portmap before trying to install nfs-common.
    • For Ubuntu/Debian OpenVZ containers, the portmap/rpcbind service may not start automatically. However, you can enable it by editing the /etc/default/nfs-common configuration file.

See also[edit]