nfsdcltrack

NFSDCLTRACK(8)                                                  NFSDCLTRACK(8)

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)