NAME

       nfsdcltrack - NFSv4 Client Tracking Callout Program

SYNOPSIS

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

DESCRIPTION

       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

       -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

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

       init
           Initialize the database. This command requires no argument.

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

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

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

LEGACY TRANSITION MECHANISM

       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 state.

NOTES

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

AUTHORS

       nfsdcltrack was developed by Jeff Layton <jlayton@redhat.com>.

                                                   2012-10-24                                     NFSDCLTRACK(8)