NFSDCLD(8)                                                        NFSDCLD(8)

NAME         top

       nfsdcld - NFSv4 Client Tracking Daemon

SYNOPSIS         top

       nfsdcld [-d] [-F] [-p path] [-s stable storage dir]

DESCRIPTION         top

       nfsdcld is the NFSv4 client tracking daemon. It is not necessary to
       run this daemon on machines that are not acting as NFSv4 servers.

       When a network partition is combined with a server reboot, there are
       edge conditions that can cause the server to grant lock reclaims when
       other clients have taken conflicting locks in the interim. A more
       detailed explanation of this issue is described in RFC 3530, section

       In order to prevent these problems, the server must track a small
       amount of per-client information on stable storage. This daemon
       provides the userspace piece of that functionality.

OPTIONS         top

       -d, --debug
           Enable debug level logging.

       -F, --foreground
           Runs the daemon in the foreground and prints all output to stderr

       -p path, --pipefsdir=path
           Location of the rpc_pipefs filesystem. The default value is

       -s storage_dir, --storagedir=storage_dir
           Directory where stable storage information should be kept. The
           default value is /var/lib/nfs/nfsdcld.


       The following values are recognized in the [nfsdcld] section of the
       /etc/nfs.conf configuration file:

           Equivalent to -s/--storagedir.

           Setting "debug = 1" is equivalent to -d/--debug.

       In addition, the following value is recognized from the [general]

           Equivalent to -p/--pipefsdir.

NOTES         top

       The Linux kernel NFSv4 server has historically tracked this
       information on stable storage by manipulating information on the
       filesystem directly, in the directory to which
       /proc/fs/nfsd/nfsv4recoverydir points.

       This changed with the original introduction of nfsdcld upcall in
       kernel version 3.4, which was later deprecated in favor of the
       nfsdcltrack(8) usermodehelper program, support for which was added in
       kernel version 3.8.  However, since the usermodehelper upcall does
       not work in containers, support for a new version of the nfsdcld
       upcall was added in kernel version 5.2.

       This daemon requires a kernel that supports the nfsdcld upcall. On
       older kernels, if the legacy client name tracking code was in use,
       then the kernel would not create the pipe that nfsdcld uses to talk
       to the kernel.  On newer kernels, nfsd attempts to initialize client
       tracking in the following order:  First, the nfsdcld upcall.  Second,
       the nfsdcltrack usermodehelper upcall.  Finally, the legacy client

       This daemon should be run as root, as the pipe that it uses to
       communicate with the kernel is only accessable by root. The daemon
       however does drop all superuser capabilities after starting. Because
       of this, the storagedir should be owned by root, and be readable and
       writable by owner.

       The daemon now supports different upcall versions to allow the kernel
       to pass additional data to be stored in the on-disk database.  The
       kernel will query the supported upcall version from nfsdcld during
       client tracking initialization.  A restart of nfsd is not necessary
       after upgrading nfsdcld, however nfsd will not use a later upcall
       version until restart.  A restart of nfsd is necessary after
       downgrading nfsdcld, to ensure that nfsd does not use an upcall
       version that nfsdcld does not support.  Additionally, a downgrade of
       nfsdcld requires the schema of the on-disk database to be downgraded
       as well.  That can be accomplished using the clddb-tool(8) utility.

FILES         top


SEE ALSO         top

       nfsdcltrack(8), clddb-tool(8)

AUTHORS         top

       The nfsdcld daemon was developed by Jeff Layton <>
       with modifications from Scott Mayhew <>.

COLOPHON         top

       This page is part of the nfs-utils (NFS utilities) project.
       Information about the project can be found at 
       ⟨⟩.  If you have a bug
       report for this manual page, see
       ⟨⟩.  This page was
       obtained from the project's upstream Git repository
       ⟨;a=summary⟩ on
       2019-11-19.  (At that time, the date of the most recent commit that
       was found in the repository was 2019-11-18.)  If you discover any
       rendering problems in this HTML version of the page, or you believe
       there is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

                                 2011-12-21                       NFSDCLD(8)

Pages that refer to this page: clddb-tool(8)