NFSDCLTRACK(8)NFSDCLTRACK(8)NAMEnfsdcltrack - NFSv4 Client Tracking Callout Program
SYNOPSISnfsdcltrack [-d] [-f] [-s stable storage dir] <command> <args...>
nfsdcltack is the NFSv4 client tracking callout program. It is not
necessary to install this daemon on machines that are not acting as
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 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.
Enable debug level logging.
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.
COMMANDSnfsdcltrack requires a command for each invocation. Supported commands
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
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.
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.
This program requires a kernel that supports the nfsdcltrack
usermodehelper upcall. This support was first added to mainline kernels
AUTHORSnfsdcltrack was developed by Jeff Layton <firstname.lastname@example.org>.