NFSDCLTRACK(8)                                                NFSDCLTRACK(8)

NAME         top

       nfsdcltrack - NFSv4 Client Tracking Callout Program

SYNOPSIS         top

       nfsdcltrack [-d] [-f] [-s stable storage dir] <command> <args...>

DESCRIPTION         top

       nfsdcltrack is the NFSv4 client tracking callout program. It is not
       necessary to install this program 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
       8.6.3 and in RFC 5661, section 8.4.3.

       In order to prevent these problems, the server must track a small
       amount of per-client information on stable storage. This program
       provides the userspace piece of that functionality. When the kernel
       needs to manipulate the database that stores this info, it will
       execute this program to handle it.

OPTIONS         top

       -d, --debug
           Enable debug level logging.

       -f, --foreground
           Log to stderr instead of syslog.

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

COMMANDS         top

       nfsdcltrack requires a command for each invocation. Supported
       commands are:

           Initialize the database. This command requires no argument.

           Create a new client record (or update the timestamp on an
           existing one). This command requires a hex-encoded nfs_client_id4
           as an argument.

           Remove a client record from the database. This command requires a
           hex-encoded nfs_client_id4 as an argument.

           Check to see if a nfs_client_id4 is allowed to reclaim. This
           command requires a hex-encoded nfs_client_id4 as an argument.

           Remove any unreclaimed client records from the database. This
           command requires a epoch boot time as an argument.


       The directory for stable storage information can be set via the file
       /etc/nfs.conf by setting the storagedir value in the nfsdcltrack
       section.  For example:
              storagedir = /shared/nfs/nfsdcltrack
       Debuging to syslog can also be enabled by setting "debug = 1" in this


       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. If the kernel passes the
       correct information, then nfsdcltrack can use it to allow a seamless
       transition from the old client tracking scheme to the new one.

       On a check operation, if there is no record of the client in the
       database, nfsdcltrack will look to see if the
       NFSDCLTRACK_LEGACY_RECDIR environment variable is set. If it is, then
       it will fetch that value and see if a directory exists by that name.
       If it does, then the check operation will succeed and the directory
       will be removed.

       On a gracedone operation, nfsdcltrack will look to see if the
       NFSDCLTRACK_LEGACY_TOPDIR environment variable is set. If it is, then
       it will attempt to clean out that directory prior to exiting.

       Note that this transition is one-way. If the machine subsequently
       reboots back into an older kernel that does not support the
       nfsdcltrack upcall then the clients will not be able to recover their

NOTES         top

       This program requires a kernel that supports the nfsdcltrack
       usermodehelper upcall. This support was first added to mainline
       kernels in 3.8.

AUTHORS         top

       nfsdcltrack was developed by Jeff Layton <>.

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
       2017-03-13.  If you discover any rendering problems in this HTML ver‐
       sion 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 man‐
       ual page), send a mail to

                                 2012-10-24                   NFSDCLTRACK(8)