utils/exportd/exportd.man

.\"@(#)nfsv4.exportd.8"
.\"
.\" Copyright (C) 2021 Red Hat <nfs@redhat.com>
.\"
.TH nfsv4.exportd 8 "02 Feb 2021"
.SH NAME
nfsv4.exportd \- NFSv4 Server Mount Daemon
.SH SYNOPSIS
.BI "/usr/sbin/nfsv4.exportd [" options "]"
.SH DESCRIPTION
The
.B nfsv4.exportd
is used to manage NFSv4 exports.
The NFS server
.RI ( nfsd )
maintains a cache of authentication and authorization information which
is used to identify the source of each request, and then what access
permissions that source has to any local filesystem.  When required
information is not found in the cache, the server sends a request to
.B nfsv4.exportd
to fill in the missing information.  
.B nfsv4.exportd
uses a table of information stored in
.B /var/lib/nfs/etab
and maintained by
.BR exportfs (8),
possibly based on the contents of 
.BR exports (5),
to respond to each request.
.SH OPTIONS
.TP
.B \-d kind " or " \-\-debug kind
Turn on debugging. Valid kinds are: all, auth, call, general and parse.
.TP
.BR \-l " or " \-\-log\-auth
Enable logging of responses to authentication and access requests from
nfsd.  Each response is then cached by the kernel for 30 minutes (or as set by
.B \-\-ttl
below), and will be refreshed after 15 minutes (half the ttl time) if
the relevant client remains active.
Note that
.B -l
is equivalent to
.B "-d auth"
and so can be enabled in
.B /etc/nfs.conf
with
.B "\[dq]debug = auth\[dq]"
in the
.B "[exportd]"
section.
.TP
.BR \-i " or " \-\-cache\-use\-ipaddr
Normally each client IP address is matched against each host identifier
(name, wildcard, netgroup etc) found in
.B /etc/exports
and a combined identity is formed from all matching identifiers.
Often many clients will map to the same combined identity so performing
this mapping reduces the number of distinct access details that the
kernel needs to store.
Specifying the
.B \-i
option suppresses this mapping so that access to each filesystem is
requested and cached separately for each client IP address.  Doing this
can increase the burden of updating the cache slightly, but can make the
log messages produced by the
.B -l
option easier to read.
.TP
.B \-T " or " \-\-ttl
Provide a time-to-live (TTL) for cached information given to the kernel.
The kernel will normally request an update if the information is needed
after half of this time has expired.  Increasing the provided number,
which is in seconds, reduces the rate of cache update requests, and this
is particularly noticeable when these requests are logged with
.BR \-l .
However increasing also means that changes to hostname to address
mappings can take longer to be noticed.
The default TTL is 1800 (30 minutes).
.TP
.B \-F " or " \-\-foreground
Run in foreground (do not daemonize)
.TP
.B \-h " or " \-\-help
Display usage message.
.TP
.BR "\-t N" " or " "\-\-num\-threads=N " or  " \-\-num\-threads N "
This option specifies the number of worker threads that 
.B nfsv4.exports
spawns.  The default is 1 thread, which is probably enough.  More
threads are usually only needed for NFS servers which need to handle
mount storms of hundreds of NFS mounts in a few seconds, or when
your DNS server is slow or unreliable.
.TP
.BR \-g " or " \-\-manage-gids
Accept requests from the kernel to map user id numbers into lists of
group id numbers for use in access control.  An NFS request will
normally (except when using Kerberos or other cryptographic
authentication) contain a user-id and a list of group-ids.  Due to a
limitation in the NFS protocol, at most 16 groups ids can be listed.
If you use the
.B \-g
flag, then the list of group ids received from the client will be
replaced by a list of group ids determined by an appropriate lookup on
the server. Note that the 'primary' group id is not affected so a
.B newgroup
command on the client will still be effective.  This function requires
a Linux Kernel with version at least 2.6.21.
.SH CONFIGURATION FILE
Many of the options that can be set on the command line can also be
controlled through values set in the
.B [exportd]
or, in some cases, the
.B [nfsd]
sections of the
.I /etc/nfs.conf
configuration file.
Values recognized in the
.B [exportd]
section include 
.B cache\-use\-ipaddr ,
.BR ttl ,
.BR manage-gids ", and"
.B debug 
which each have the same effect as the option with the same name.
.SH FILES
.TP 2.5i
.I /etc/exports
input file for
.BR exportfs ,
listing exports, export options, and access control lists
.SH SEE ALSO
.BR exportfs (8),
.BR exports (5),
.BR showmount (8),
.BR nfs.conf (5),
.BR firewall-cmd (1),
.sp
RFC 7530 - "Network File System (NFS) Version 4 Protocol"
.br
RFC 8881 - "Network File System (NFS) Version 4 Minor Version 1 Protocol"