NAMEnfsdcltrack - NFSv4 Client Tracking Callout Program
SYNOPSISnfsdcltrack [-d] [-f] [-s stable storage dir] <command> <args...>
DESCRIPTIONnfsdcltrack 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
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.
- -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.
COMMANDSnfsdcltrack 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.
LEGACY TRANSITION MECHANISMThe 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
On a gracedone operation, nfsdcltrack will look to see if the
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.