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nfsdcld - NFSv4 Client Tracking Daemon

nfsdcld [-d] [-F] [-p path] [-s stable storage dir]

nfsdcld is the NFSv4 client tracking daemon. It is not necessary to run this daemon 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.

In order to prevent these problems, the server must track a small amount of per-client information on stable storage. This daemon provides the userspace piece of that functionality.

-d, --debug
Enable debug level logging.
-F, --foreground
Runs the daemon in the foreground and prints all output to stderr
-p path, --pipefsdir=path
Location of the rpc_pipefs filesystem. The default value is /var/lib/nfs/rpc_pipefs.
-s storage_dir, --storagedir=storage_dir
Directory where stable storage information should be kept. The default value is /var/lib/nfs/nfsdcld.

The following values are recognized in the [nfsdcld] section of the /etc/nfs.conf configuration file:
Equivalent to -s/--storagedir.
Setting "debug = 1" is equivalent to -d/--debug.

In addition, the following value is recognized from the [general] section:

Equivalent to -p/--pipefsdir.

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.

This daemon requires a kernel that supports the nfsdcld upcall. If the kernel does not support the new upcall, or is using the legacy client name tracking code then it will not create the pipe that nfsdcld uses to talk to the kernel.

This daemon should be run as root, as the pipe that it uses to communicate with the kernel is only accessable by root. The daemon however does drop all superuser capabilities after starting. Because of this, the storagedir should be owned by root, and be readable and writable by owner.

The nfsdcld daemon was developed by Jeff Layton <>.