.\" Copyright (c) 2009 Rick Macklem, University of Guelph
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.Dd April 25, 2009
.Dt NFSCBD 8
.Os
.Sh NAME
.Nm nfscbd
.Nd
.Tn NFSv4
client side callback daemon
.Sh SYNOPSIS
.Nm nfscbd
.Op Fl p Ar port_number
.Op Fl P Ar client_principal
.Sh DESCRIPTION
.Nm
runs on a client using
.Tn NFSv4
to handle callback requests from the NFSv4 server.
If no
.Nm
is running, NFSv4 mounts will still work, but the server will never issue
Open Delegations to the client.
.Pp
One callback server and one master server
are always started.
.Pp
The following options are available:
.Bl -tag -width Ds
.It Fl p Ar port_number
Specifies what port# the callback server should use.
.It Fl P Ar client_principal
Specifies the host based principal name to be used as the target for
callbacks over RPCSEC_GSS. For KerberosV, it must be in the client's
default keytab file.
This client_principal should be the same one specified by the
.Cm gssname
argument being used by nfsv4 mounts.
If you do not specify this argument, callbacks will still work over AUTH_SYS,
which is what many extant servers use even for RPCSEC_GSS mounts, as of 2009.
.El
.Pp
For example,
.Dq Li "nfscbd -p 7654 -P root"
starts the daemon to handle callbacks on port# 7654 and is using the host based
principal root@<client-host>.<dns-domain> as the callback target.
.Pp
.Nm
listens for service requests at the port
defined by NFSV4_CBPORT in /usr/include/fs/nfs/nfs.h, unless
.Fl p
has been specified.
For more information on what callbacks and Open Delegations do, see
.%T "Network File System (NFS) Version 4 Protocol" ,
RFC3530.
.Sh EXIT STATUS
.Ex -std
.Sh SEE ALSO
.Xr nfsv4 4 ,
.Xr mount_nfs 8
.Sh HISTORY
First introduced with the experimental nfs client for NFSv4 support in 2009.