nfsdcld(8) — Linux manual page


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

       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 8.6.3.

       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

       -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 tracking.

       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 nfsdclddb(8) utility.

FILES         top


SEE ALSO         top

       nfsdcltrack(8), nfsdclddb(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
       2021-08-27.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-08-21.)  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
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       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: nfsdclddb(8)